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This is gdb.info, produced by makeinfo version 4.8 from
../.././gdb/doc/gdb.texinfo.
INFO-DIR-SECTION Software development
START-INFO-DIR-ENTRY
* Gdb: (gdb). The GNU debugger.
END-INFO-DIR-ENTRY
This file documents the GNU debugger GDB.
This is the Ninth Edition, of `Debugging with GDB: the GNU
Source-Level Debugger' for GDB Version 6.6.
Copyright (C) 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996,
1998,
1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006
Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with the
Invariant Sections being "Free Software" and "Free Software Needs Free
Documentation", with the Front-Cover Texts being "A GNU Manual," and
with the Back-Cover Texts as in (a) below.
(a) The Free Software Foundation's Back-Cover Text is: "You have
freedom to copy and modify this GNU Manual, like GNU software. Copies
published by the Free Software Foundation raise funds for GNU
development."

File: gdb.info, Node: GDB/MI Breakpoint Commands, Next: GDB/MI Program Context, Prev: GDB/MI Command Description Format, Up: GDB/MI
24.7 GDB/MI Breakpoint Commands
===============================
This section documents GDB/MI commands for manipulating breakpoints.
The `-break-after' Command
--------------------------
Synopsis
........
-break-after NUMBER COUNT
The breakpoint number NUMBER is not in effect until it has been hit
COUNT times. To see how this is reflected in the output of the
`-break-list' command, see the description of the `-break-list' command
below.
GDB Command
...........
The corresponding GDB command is `ignore'.
Example
.......
(gdb)
-break-insert main
^done,bkpt={number="1",addr="0x000100d0",file="hello.c",
fullname="/home/foo/hello.c",line="5",times="0"}
(gdb)
-break-after 1 3
~
^done
(gdb)
-break-list
^done,BreakpointTable={nr_rows="1",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",
addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
line="5",times="0",ignore="3"}]}
(gdb)
The `-break-condition' Command
------------------------------
Synopsis
........
-break-condition NUMBER EXPR
Breakpoint NUMBER will stop the program only if the condition in
EXPR is true. The condition becomes part of the `-break-list' output
(see the description of the `-break-list' command below).
GDB Command
...........
The corresponding GDB command is `condition'.
Example
.......
(gdb)
-break-condition 1 1
^done
(gdb)
-break-list
^done,BreakpointTable={nr_rows="1",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",
addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
line="5",cond="1",times="0",ignore="3"}]}
(gdb)
The `-break-delete' Command
---------------------------
Synopsis
........
-break-delete ( BREAKPOINT )+
Delete the breakpoint(s) whose number(s) are specified in the
argument list. This is obviously reflected in the breakpoint list.
GDB command
...........
The corresponding GDB command is `delete'.
Example
.......
(gdb)
-break-delete 1
^done
(gdb)
-break-list
^done,BreakpointTable={nr_rows="0",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[]}
(gdb)
The `-break-disable' Command
----------------------------
Synopsis
........
-break-disable ( BREAKPOINT )+
Disable the named BREAKPOINT(s). The field `enabled' in the break
list is now set to `n' for the named BREAKPOINT(s).
GDB Command
...........
The corresponding GDB command is `disable'.
Example
.......
(gdb)
-break-disable 2
^done
(gdb)
-break-list
^done,BreakpointTable={nr_rows="1",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="2",type="breakpoint",disp="keep",enabled="n",
addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
line="5",times="0"}]}
(gdb)
The `-break-enable' Command
---------------------------
Synopsis
........
-break-enable ( BREAKPOINT )+
Enable (previously disabled) BREAKPOINT(s).
GDB Command
...........
The corresponding GDB command is `enable'.
Example
.......
(gdb)
-break-enable 2
^done
(gdb)
-break-list
^done,BreakpointTable={nr_rows="1",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="2",type="breakpoint",disp="keep",enabled="y",
addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
line="5",times="0"}]}
(gdb)
The `-break-info' Command
-------------------------
Synopsis
........
-break-info BREAKPOINT
Get information about a single breakpoint.
GDB command
...........
The corresponding GDB command is `info break BREAKPOINT'.
Example
.......
N.A.
The `-break-insert' Command
---------------------------
Synopsis
........
-break-insert [ -t ] [ -h ] [ -r ]
[ -c CONDITION ] [ -i IGNORE-COUNT ]
[ -p THREAD ] [ LINE | ADDR ]
If specified, LINE, can be one of:
* function
* filename:linenum
* filename:function
* *address
The possible optional parameters of this command are:
`-t'
Insert a temporary breakpoint.
`-h'
Insert a hardware breakpoint.
`-c CONDITION'
Make the breakpoint conditional on CONDITION.
`-i IGNORE-COUNT'
Initialize the IGNORE-COUNT.
`-r'
Insert a regular breakpoint in all the functions whose names match
the given regular expression. Other flags are not applicable to
regular expresson.
Result
......
The result is in the form:
^done,bkpt={number="NUMBER",type="TYPE",disp="del"|"keep",
enabled="y"|"n",addr="HEX",func="FUNCNAME",file="FILENAME",
fullname="FULL_FILENAME",line="LINENO",[thread="THREADNO,]
times="TIMES"}
where NUMBER is the GDB number for this breakpoint, FUNCNAME is the
name of the function where the breakpoint was inserted, FILENAME is the
name of the source file which contains this function, LINENO is the
source line number within that file and TIMES the number of times that
the breakpoint has been hit (always 0 for -break-insert but may be
greater for -break-info or -break-list which use the same output).
Note: this format is open to change.
GDB Command
...........
The corresponding GDB commands are `break', `tbreak', `hbreak',
`thbreak', and `rbreak'.
Example
.......
(gdb)
-break-insert main
^done,bkpt={number="1",addr="0x0001072c",file="recursive2.c",
fullname="/home/foo/recursive2.c,line="4",times="0"}
(gdb)
-break-insert -t foo
^done,bkpt={number="2",addr="0x00010774",file="recursive2.c",
fullname="/home/foo/recursive2.c,line="11",times="0"}
(gdb)
-break-list
^done,BreakpointTable={nr_rows="2",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",
addr="0x0001072c", func="main",file="recursive2.c",
fullname="/home/foo/recursive2.c,"line="4",times="0"},
bkpt={number="2",type="breakpoint",disp="del",enabled="y",
addr="0x00010774",func="foo",file="recursive2.c",
fullname="/home/foo/recursive2.c",line="11",times="0"}]}
(gdb)
-break-insert -r foo.*
~int foo(int, int);
^done,bkpt={number="3",addr="0x00010774",file="recursive2.c,
"fullname="/home/foo/recursive2.c",line="11",times="0"}
(gdb)
The `-break-list' Command
-------------------------
Synopsis
........
-break-list
Displays the list of inserted breakpoints, showing the following
fields:
`Number'
number of the breakpoint
`Type'
type of the breakpoint: `breakpoint' or `watchpoint'
`Disposition'
should the breakpoint be deleted or disabled when it is hit: `keep'
or `nokeep'
`Enabled'
is the breakpoint enabled or no: `y' or `n'
`Address'
memory location at which the breakpoint is set
`What'
logical location of the breakpoint, expressed by function name,
file name, line number
`Times'
number of times the breakpoint has been hit
If there are no breakpoints or watchpoints, the `BreakpointTable'
`body' field is an empty list.
GDB Command
...........
The corresponding GDB command is `info break'.
Example
.......
(gdb)
-break-list
^done,BreakpointTable={nr_rows="2",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",
addr="0x000100d0",func="main",file="hello.c",line="5",times="0"},
bkpt={number="2",type="breakpoint",disp="keep",enabled="y",
addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
line="13",times="0"}]}
(gdb)
Here's an example of the result when there are no breakpoints:
(gdb)
-break-list
^done,BreakpointTable={nr_rows="0",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[]}
(gdb)
The `-break-watch' Command
--------------------------
Synopsis
........
-break-watch [ -a | -r ]
Create a watchpoint. With the `-a' option it will create an
"access" watchpoint, i.e. a watchpoint that triggers either on a read
from or on a write to the memory location. With the `-r' option, the
watchpoint created is a "read" watchpoint, i.e. it will trigger only
when the memory location is accessed for reading. Without either of
the options, the watchpoint created is a regular watchpoint, i.e. it
will trigger when the memory location is accessed for writing. *Note
Setting watchpoints: Set Watchpoints.
Note that `-break-list' will report a single list of watchpoints and
breakpoints inserted.
GDB Command
...........
The corresponding GDB commands are `watch', `awatch', and `rwatch'.
Example
.......
Setting a watchpoint on a variable in the `main' function:
(gdb)
-break-watch x
^done,wpt={number="2",exp="x"}
(gdb)
-exec-continue
^running
^done,reason="watchpoint-trigger",wpt={number="2",exp="x"},
value={old="-268439212",new="55"},
frame={func="main",args=[],file="recursive2.c",
fullname="/home/foo/bar/recursive2.c",line="5"}
(gdb)
Setting a watchpoint on a variable local to a function. GDB will
stop the program execution twice: first for the variable changing
value, then for the watchpoint going out of scope.
(gdb)
-break-watch C
^done,wpt={number="5",exp="C"}
(gdb)
-exec-continue
^running
^done,reason="watchpoint-trigger",
wpt={number="5",exp="C"},value={old="-276895068",new="3"},
frame={func="callee4",args=[],
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"}
(gdb)
-exec-continue
^running
^done,reason="watchpoint-scope",wpnum="5",
frame={func="callee3",args=[{name="strarg",
value="0x11940 \"A string argument.\""}],
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"}
(gdb)
Listing breakpoints and watchpoints, at different points in the
program execution. Note that once the watchpoint goes out of scope, it
is deleted.
(gdb)
-break-watch C
^done,wpt={number="2",exp="C"}
(gdb)
-break-list
^done,BreakpointTable={nr_rows="2",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",
addr="0x00010734",func="callee4",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",times="1"},
bkpt={number="2",type="watchpoint",disp="keep",
enabled="y",addr="",what="C",times="0"}]}
(gdb)
-exec-continue
^running
^done,reason="watchpoint-trigger",wpt={number="2",exp="C"},
value={old="-276895068",new="3"},
frame={func="callee4",args=[],
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"}
(gdb)
-break-list
^done,BreakpointTable={nr_rows="2",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",
addr="0x00010734",func="callee4",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",times="1"},
bkpt={number="2",type="watchpoint",disp="keep",
enabled="y",addr="",what="C",times="-5"}]}
(gdb)
-exec-continue
^running
^done,reason="watchpoint-scope",wpnum="2",
frame={func="callee3",args=[{name="strarg",
value="0x11940 \"A string argument.\""}],
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"}
(gdb)
-break-list
^done,BreakpointTable={nr_rows="1",nr_cols="6",
hdr=[{width="3",alignment="-1",col_name="number",colhdr="Num"},
{width="14",alignment="-1",col_name="type",colhdr="Type"},
{width="4",alignment="-1",col_name="disp",colhdr="Disp"},
{width="3",alignment="-1",col_name="enabled",colhdr="Enb"},
{width="10",alignment="-1",col_name="addr",colhdr="Address"},
{width="40",alignment="2",col_name="what",colhdr="What"}],
body=[bkpt={number="1",type="breakpoint",disp="keep",enabled="y",
addr="0x00010734",func="callee4",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
times="1"}]}
(gdb)

File: gdb.info, Node: GDB/MI Program Context, Next: GDB/MI Thread Commands, Prev: GDB/MI Breakpoint Commands, Up: GDB/MI
24.8 GDB/MI Program Context
============================
The `-exec-arguments' Command
-----------------------------
Synopsis
........
-exec-arguments ARGS
Set the inferior program arguments, to be used in the next
`-exec-run'.
GDB Command
...........
The corresponding GDB command is `set args'.
Example
.......
Don't have one around.
The `-exec-show-arguments' Command
----------------------------------
Synopsis
........
-exec-show-arguments
Print the arguments of the program.
GDB Command
...........
The corresponding GDB command is `show args'.
Example
.......
N.A.
The `-environment-cd' Command
-----------------------------
Synopsis
........
-environment-cd PATHDIR
Set GDB's working directory.
GDB Command
...........
The corresponding GDB command is `cd'.
Example
.......
(gdb)
-environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
^done
(gdb)
The `-environment-directory' Command
------------------------------------
Synopsis
........
-environment-directory [ -r ] [ PATHDIR ]+
Add directories PATHDIR to beginning of search path for source files.
If the `-r' option is used, the search path is reset to the default
search path. If directories PATHDIR are supplied in addition to the
`-r' option, the search path is first reset and then addition occurs as
normal. Multiple directories may be specified, separated by blanks.
Specifying multiple directories in a single command results in the
directories added to the beginning of the search path in the same order
they were presented in the command. If blanks are needed as part of a
directory name, double-quotes should be used around the name. In the
command output, the path will show up separated by the system
directory-separator character. The directory-seperator character must
not be used in any directory name. If no directories are specified,
the current search path is displayed.
GDB Command
...........
The corresponding GDB command is `dir'.
Example
.......
(gdb)
-environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
(gdb)
-environment-directory ""
^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
(gdb)
-environment-directory -r /home/jjohnstn/src/gdb /usr/src
^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
(gdb)
-environment-directory -r
^done,source-path="$cdir:$cwd"
(gdb)
The `-environment-path' Command
-------------------------------
Synopsis
........
-environment-path [ -r ] [ PATHDIR ]+
Add directories PATHDIR to beginning of search path for object files.
If the `-r' option is used, the search path is reset to the original
search path that existed at gdb start-up. If directories PATHDIR are
supplied in addition to the `-r' option, the search path is first reset
and then addition occurs as normal. Multiple directories may be
specified, separated by blanks. Specifying multiple directories in a
single command results in the directories added to the beginning of the
search path in the same order they were presented in the command. If
blanks are needed as part of a directory name, double-quotes should be
used around the name. In the command output, the path will show up
separated by the system directory-separator character. The
directory-seperator character must not be used in any directory name.
If no directories are specified, the current path is displayed.
GDB Command
...........
The corresponding GDB command is `path'.
Example
.......
(gdb)
-environment-path
^done,path="/usr/bin"
(gdb)
-environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
(gdb)
-environment-path -r /usr/local/bin
^done,path="/usr/local/bin:/usr/bin"
(gdb)
The `-environment-pwd' Command
------------------------------
Synopsis
........
-environment-pwd
Show the current working directory.
GDB command
...........
The corresponding GDB command is `pwd'.
Example
.......
(gdb)
-environment-pwd
^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
(gdb)

File: gdb.info, Node: GDB/MI Thread Commands, Next: GDB/MI Program Execution, Prev: GDB/MI Program Context, Up: GDB/MI
24.9 GDB/MI Thread Commands
===========================
The `-thread-info' Command
--------------------------
Synopsis
........
-thread-info
GDB command
...........
No equivalent.
Example
.......
N.A.
The `-thread-list-all-threads' Command
--------------------------------------
Synopsis
........
-thread-list-all-threads
GDB Command
...........
The equivalent GDB command is `info threads'.
Example
.......
N.A.
The `-thread-list-ids' Command
------------------------------
Synopsis
........
-thread-list-ids
Produces a list of the currently known GDB thread ids. At the end
of the list it also prints the total number of such threads.
GDB Command
...........
Part of `info threads' supplies the same information.
Example
.......
No threads present, besides the main process:
(gdb)
-thread-list-ids
^done,thread-ids={},number-of-threads="0"
(gdb)
Several threads:
(gdb)
-thread-list-ids
^done,thread-ids={thread-id="3",thread-id="2",thread-id="1"},
number-of-threads="3"
(gdb)
The `-thread-select' Command
----------------------------
Synopsis
........
-thread-select THREADNUM
Make THREADNUM the current thread. It prints the number of the new
current thread, and the topmost frame for that thread.
GDB Command
...........
The corresponding GDB command is `thread'.
Example
.......
(gdb)
-exec-next
^running
(gdb)
*stopped,reason="end-stepping-range",thread-id="2",line="187",
file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
(gdb)
-thread-list-ids
^done,
thread-ids={thread-id="3",thread-id="2",thread-id="1"},
number-of-threads="3"
(gdb)
-thread-select 3
^done,new-thread-id="3",
frame={level="0",func="vprintf",
args=[{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""},
{name="arg",value="0x2"}],file="vprintf.c",line="31"}
(gdb)

File: gdb.info, Node: GDB/MI Program Execution, Next: GDB/MI Stack Manipulation, Prev: GDB/MI Thread Commands, Up: GDB/MI
24.10 GDB/MI Program Execution
==============================
These are the asynchronous commands which generate the out-of-band
record `*stopped'. Currently GDB only really executes asynchronously
with remote targets and this interaction is mimicked in other cases.
The `-exec-continue' Command
----------------------------
Synopsis
........
-exec-continue
Resumes the execution of the inferior program until a breakpoint is
encountered, or until the inferior exits.
GDB Command
...........
The corresponding GDB corresponding is `continue'.
Example
.......
-exec-continue
^running
(gdb)
@Hello world
*stopped,reason="breakpoint-hit",bkptno="2",frame={func="foo",args=[],
file="hello.c",fullname="/home/foo/bar/hello.c",line="13"}
(gdb)
The `-exec-finish' Command
--------------------------
Synopsis
........
-exec-finish
Resumes the execution of the inferior program until the current
function is exited. Displays the results returned by the function.
GDB Command
...........
The corresponding GDB command is `finish'.
Example
.......
Function returning `void'.
-exec-finish
^running
(gdb)
@hello from foo
*stopped,reason="function-finished",frame={func="main",args=[],
file="hello.c",fullname="/home/foo/bar/hello.c",line="7"}
(gdb)
Function returning other than `void'. The name of the internal GDB
variable storing the result is printed, together with the value itself.
-exec-finish
^running
(gdb)
*stopped,reason="function-finished",frame={addr="0x000107b0",func="foo",
args=[{name="a",value="1"],{name="b",value="9"}},
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
gdb-result-var="$1",return-value="0"
(gdb)
The `-exec-interrupt' Command
-----------------------------
Synopsis
........
-exec-interrupt
Interrupts the background execution of the target. Note how the
token associated with the stop message is the one for the execution
command that has been interrupted. The token for the interrupt itself
only appears in the `^done' output. If the user is trying to interrupt
a non-running program, an error message will be printed.
GDB Command
...........
The corresponding GDB command is `interrupt'.
Example
.......
(gdb)
111-exec-continue
111^running
(gdb)
222-exec-interrupt
222^done
(gdb)
111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
frame={addr="0x00010140",func="foo",args=[],file="try.c",
fullname="/home/foo/bar/try.c",line="13"}
(gdb)
(gdb)
-exec-interrupt
^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
(gdb)
The `-exec-next' Command
------------------------
Synopsis
........
-exec-next
Resumes execution of the inferior program, stopping when the
beginning of the next source line is reached.
GDB Command
...........
The corresponding GDB command is `next'.
Example
.......
-exec-next
^running
(gdb)
*stopped,reason="end-stepping-range",line="8",file="hello.c"
(gdb)
The `-exec-next-instruction' Command
------------------------------------
Synopsis
........
-exec-next-instruction
Executes one machine instruction. If the instruction is a function
call, continues until the function returns. If the program stops at an
instruction in the middle of a source line, the address will be printed
as well.
GDB Command
...........
The corresponding GDB command is `nexti'.
Example
.......
(gdb)
-exec-next-instruction
^running
(gdb)
*stopped,reason="end-stepping-range",
addr="0x000100d4",line="5",file="hello.c"
(gdb)
The `-exec-return' Command
--------------------------
Synopsis
........
-exec-return
Makes current function return immediately. Doesn't execute the
inferior. Displays the new current frame.
GDB Command
...........
The corresponding GDB command is `return'.
Example
.......
(gdb)
200-break-insert callee4
200^done,bkpt={number="1",addr="0x00010734",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"}
(gdb)
000-exec-run
000^running
(gdb)
000*stopped,reason="breakpoint-hit",bkptno="1",
frame={func="callee4",args=[],
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"}
(gdb)
205-break-delete
205^done
(gdb)
111-exec-return
111^done,frame={level="0",func="callee3",
args=[{name="strarg",
value="0x11940 \"A string argument.\""}],
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"}
(gdb)
The `-exec-run' Command
-----------------------
Synopsis
........
-exec-run
Starts execution of the inferior from the beginning. The inferior
executes until either a breakpoint is encountered or the program exits.
In the latter case the output will include an exit code, if the
program has exited exceptionally.
GDB Command
...........
The corresponding GDB command is `run'.
Examples
........
(gdb)
-break-insert main
^done,bkpt={number="1",addr="0x0001072c",file="recursive2.c",line="4"}
(gdb)
-exec-run
^running
(gdb)
*stopped,reason="breakpoint-hit",bkptno="1",
frame={func="main",args=[],file="recursive2.c",
fullname="/home/foo/bar/recursive2.c",line="4"}
(gdb)
Program exited normally:
(gdb)
-exec-run
^running
(gdb)
x = 55
*stopped,reason="exited-normally"
(gdb)
Program exited exceptionally:
(gdb)
-exec-run
^running
(gdb)
x = 55
*stopped,reason="exited",exit-code="01"
(gdb)
Another way the program can terminate is if it receives a signal
such as `SIGINT'. In this case, GDB/MI displays this:
(gdb)
*stopped,reason="exited-signalled",signal-name="SIGINT",
signal-meaning="Interrupt"
The `-exec-step' Command
------------------------
Synopsis
........
-exec-step
Resumes execution of the inferior program, stopping when the
beginning of the next source line is reached, if the next source line
is not a function call. If it is, stop at the first instruction of the
called function.
GDB Command
...........
The corresponding GDB command is `step'.
Example
.......
Stepping into a function:
-exec-step
^running
(gdb)
*stopped,reason="end-stepping-range",
frame={func="foo",args=[{name="a",value="10"},
{name="b",value="0"}],file="recursive2.c",
fullname="/home/foo/bar/recursive2.c",line="11"}
(gdb)
Regular stepping:
-exec-step
^running
(gdb)
*stopped,reason="end-stepping-range",line="14",file="recursive2.c"
(gdb)
The `-exec-step-instruction' Command
------------------------------------
Synopsis
........
-exec-step-instruction
Resumes the inferior which executes one machine instruction. The
output, once GDB has stopped, will vary depending on whether we have
stopped in the middle of a source line or not. In the former case, the
address at which the program stopped will be printed as well.
GDB Command
...........
The corresponding GDB command is `stepi'.
Example
.......
(gdb)
-exec-step-instruction
^running
(gdb)
*stopped,reason="end-stepping-range",
frame={func="foo",args=[],file="try.c",
fullname="/home/foo/bar/try.c",line="10"}
(gdb)
-exec-step-instruction
^running
(gdb)
*stopped,reason="end-stepping-range",
frame={addr="0x000100f4",func="foo",args=[],file="try.c",
fullname="/home/foo/bar/try.c",line="10"}
(gdb)
The `-exec-until' Command
-------------------------
Synopsis
........
-exec-until [ LOCATION ]
Executes the inferior until the LOCATION specified in the argument
is reached. If there is no argument, the inferior executes until a
source line greater than the current one is reached. The reason for
stopping in this case will be `location-reached'.
GDB Command
...........
The corresponding GDB command is `until'.
Example
.......
(gdb)
-exec-until recursive2.c:6
^running
(gdb)
x = 55
*stopped,reason="location-reached",frame={func="main",args=[],
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"}
(gdb)

File: gdb.info, Node: GDB/MI Stack Manipulation, Next: GDB/MI Variable Objects, Prev: GDB/MI Program Execution, Up: GDB/MI
24.11 GDB/MI Stack Manipulation Commands
========================================
The `-stack-info-frame' Command
-------------------------------
Synopsis
........
-stack-info-frame
Get info on the selected frame.
GDB Command
...........
The corresponding GDB command is `info frame' or `frame' (without
arguments).
Example
.......
(gdb)
-stack-info-frame
^done,frame={level="1",addr="0x0001076c",func="callee3",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"}
(gdb)
The `-stack-info-depth' Command
-------------------------------
Synopsis
........
-stack-info-depth [ MAX-DEPTH ]
Return the depth of the stack. If the integer argument MAX-DEPTH is
specified, do not count beyond MAX-DEPTH frames.
GDB Command
...........
There's no equivalent GDB command.
Example
.......
For a stack with frame levels 0 through 11:
(gdb)
-stack-info-depth
^done,depth="12"
(gdb)
-stack-info-depth 4
^done,depth="4"
(gdb)
-stack-info-depth 12
^done,depth="12"
(gdb)
-stack-info-depth 11
^done,depth="11"
(gdb)
-stack-info-depth 13
^done,depth="12"
(gdb)
The `-stack-list-arguments' Command
-----------------------------------
Synopsis
........
-stack-list-arguments SHOW-VALUES
[ LOW-FRAME HIGH-FRAME ]
Display a list of the arguments for the frames between LOW-FRAME and
HIGH-FRAME (inclusive). If LOW-FRAME and HIGH-FRAME are not provided,
list the arguments for the whole call stack. If the two arguments are
equal, show the single frame at the corresponding level. It is an
error if LOW-FRAME is larger than the actual number of frames. On the
other hand, HIGH-FRAME may be larger than the actual number of frames,
in which case only existing frames will be returned.
The SHOW-VALUES argument must have a value of 0 or 1. A value of 0
means that only the names of the arguments are listed, a value of 1
means that both names and values of the arguments are printed.
GDB Command
...........
GDB does not have an equivalent command. `gdbtk' has a `gdb_get_args'
command which partially overlaps with the functionality of
`-stack-list-arguments'.
Example
.......
(gdb)
-stack-list-frames
^done,
stack=[
frame={level="0",addr="0x00010734",func="callee4",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"},
frame={level="1",addr="0x0001076c",func="callee3",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"},
frame={level="2",addr="0x0001078c",func="callee2",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"},
frame={level="3",addr="0x000107b4",func="callee1",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"},
frame={level="4",addr="0x000107e0",func="main",
file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"}]
(gdb)
-stack-list-arguments 0
^done,
stack-args=[
frame={level="0",args=[]},
frame={level="1",args=[name="strarg"]},
frame={level="2",args=[name="intarg",name="strarg"]},
frame={level="3",args=[name="intarg",name="strarg",name="fltarg"]},
frame={level="4",args=[]}]
(gdb)
-stack-list-arguments 1
^done,
stack-args=[
frame={level="0",args=[]},
frame={level="1",
args=[{name="strarg",value="0x11940 \"A string argument.\""}]},
frame={level="2",args=[
{name="intarg",value="2"},
{name="strarg",value="0x11940 \"A string argument.\""}]},
{frame={level="3",args=[
{name="intarg",value="2"},
{name="strarg",value="0x11940 \"A string argument.\""},
{name="fltarg",value="3.5"}]},
frame={level="4",args=[]}]
(gdb)
-stack-list-arguments 0 2 2
^done,stack-args=[frame={level="2",args=[name="intarg",name="strarg"]}]
(gdb)
-stack-list-arguments 1 2 2
^done,stack-args=[frame={level="2",
args=[{name="intarg",value="2"},
{name="strarg",value="0x11940 \"A string argument.\""}]}]
(gdb)
The `-stack-list-frames' Command
--------------------------------
Synopsis
........
-stack-list-frames [ LOW-FRAME HIGH-FRAME ]
List the frames currently on the stack. For each frame it displays
the following info:
`LEVEL'
The frame number, 0 being the topmost frame, i.e. the innermost
function.
`ADDR'
The `$pc' value for that frame.
`FUNC'
Function name.
`FILE'
File name of the source file where the function lives.
`LINE'
Line number corresponding to the `$pc'.
If invoked without arguments, this command prints a backtrace for the
whole stack. If given two integer arguments, it shows the frames whose
levels are between the two arguments (inclusive). If the two arguments
are equal, it shows the single frame at the corresponding level. It is
an error if LOW-FRAME is larger than the actual number of frames. On
the other hand, HIGH-FRAME may be larger than the actual number of
frames, in which case only existing frames will be returned.
GDB Command
...........
The corresponding GDB commands are `backtrace' and `where'.
Example
.......
Full stack backtrace:
(gdb)
-stack-list-frames
^done,stack=
[frame={level="0",addr="0x0001076c",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"},
frame={level="1",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="2",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="3",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="4",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="5",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="6",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="7",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="8",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="9",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="10",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="11",addr="0x00010738",func="main",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"}]
(gdb)
Show frames between LOW_FRAME and HIGH_FRAME:
(gdb)
-stack-list-frames 3 5
^done,stack=
[frame={level="3",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="4",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"},
frame={level="5",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"}]
(gdb)
Show a single frame:
(gdb)
-stack-list-frames 3 3
^done,stack=
[frame={level="3",addr="0x000107a4",func="foo",
file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"}]
(gdb)
The `-stack-list-locals' Command
--------------------------------
Synopsis
........
-stack-list-locals PRINT-VALUES
Display the local variable names for the selected frame. If
PRINT-VALUES is 0 or `--no-values', print only the names of the
variables; if it is 1 or `--all-values', print also their values; and
if it is 2 or `--simple-values', print the name, type and value for
simple data types and the name and type for arrays, structures and
unions. In this last case, a frontend can immediately display the
value of simple data types and create variable objects for other data
types when the the user wishes to explore their values in more detail.
GDB Command
...........
`info locals' in GDB, `gdb_get_locals' in `gdbtk'.
Example
.......
(gdb)
-stack-list-locals 0
^done,locals=[name="A",name="B",name="C"]
(gdb)
-stack-list-locals --all-values
^done,locals=[{name="A",value="1"},{name="B",value="2"},
{name="C",value="{1, 2, 3}"}]
-stack-list-locals --simple-values
^done,locals=[{name="A",type="int",value="1"},
{name="B",type="int",value="2"},{name="C",type="int [3]"}]
(gdb)
The `-stack-select-frame' Command
---------------------------------
Synopsis
........
-stack-select-frame FRAMENUM
Change the selected frame. Select a different frame FRAMENUM on the
stack.
GDB Command
...........
The corresponding GDB commands are `frame', `up', `down',
`select-frame', `up-silent', and `down-silent'.
Example
.......
(gdb)
-stack-select-frame 2
^done
(gdb)

File: gdb.info, Node: GDB/MI Variable Objects, Next: GDB/MI Data Manipulation, Prev: GDB/MI Stack Manipulation, Up: GDB/MI
24.12 GDB/MI Variable Objects
=============================
Motivation for Variable Objects in GDB/MI
-----------------------------------------
For the implementation of a variable debugger window (locals, watched
expressions, etc.), we are proposing the adaptation of the existing code
used by `Insight'.
The two main reasons for that are:
1. It has been proven in practice (it is already on its second
generation).
2. It will shorten development time (needless to say how important it
is now).
The original interface was designed to be used by Tcl code, so it was
slightly changed so it could be used through GDB/MI. This section
describes the GDB/MI operations that will be available and gives some
hints about their use.
_Note_: In addition to the set of operations described here, we
expect the GUI implementation of a variable window to require, at
least, the following operations:
* `-gdb-show' `output-radix'
* `-stack-list-arguments'
* `-stack-list-locals'
* `-stack-select-frame'
Introduction to Variable Objects in GDB/MI
------------------------------------------
The basic idea behind variable objects is the creation of a named object
to represent a variable, an expression, a memory location or even a CPU
register. For each object created, a set of operations is available for
examining or changing its properties.
Furthermore, complex data types, such as C structures, are
represented in a tree format. For instance, the `struct' type variable
is the root and the children will represent the struct members. If a
child is itself of a complex type, it will also have children of its
own. Appropriate language differences are handled for C, C++ and Java.
When returning the actual values of the objects, this facility allows
for the individual selection of the display format used in the result
creation. It can be chosen among: binary, decimal, hexadecimal, octal
and natural. Natural refers to a default format automatically chosen
based on the variable type (like decimal for an `int', hex for
pointers, etc.).
The following is the complete set of GDB/MI operations defined to
access this functionality:
*Operation* *Description*
`-var-create' create a variable object
`-var-delete' delete the variable object and its children
`-var-set-format' set the display format of this variable
`-var-show-format' show the display format of this variable
`-var-info-num-children' tells how many children this object has
`-var-list-children' return a list of the object's children
`-var-info-type' show the type of this variable object
`-var-info-expression' print what this variable object represents
`-var-show-attributes' is this variable editable? does it exist
here?
`-var-evaluate-expression' get the value of this variable
`-var-assign' set the value of this variable
`-var-update' update the variable and its children
In the next subsection we describe each operation in detail and
suggest how it can be used.
Description And Use of Operations on Variable Objects
-----------------------------------------------------
The `-var-create' Command
-------------------------
Synopsis
........
-var-create {NAME | "-"}
{FRAME-ADDR | "*"} EXPRESSION
This operation creates a variable object, which allows the
monitoring of a variable, the result of an expression, a memory cell or
a CPU register.
The NAME parameter is the string by which the object can be
referenced. It must be unique. If `-' is specified, the varobj system
will generate a string "varNNNNNN" automatically. It will be unique
provided that one does not specify NAME on that format. The command
fails if a duplicate name is found.
The frame under which the expression should be evaluated can be
specified by FRAME-ADDR. A `*' indicates that the current frame should
be used.
EXPRESSION is any expression valid on the current language set (must
not begin with a `*'), or one of the following:
* `*ADDR', where ADDR is the address of a memory cell
* `*ADDR-ADDR' -- a memory address range (TBD)
* `$REGNAME' -- a CPU register name
Result
......
This operation returns the name, number of children and the type of the
object created. Type is returned as a string as the ones generated by
the GDB CLI:
name="NAME",numchild="N",type="TYPE"
The `-var-delete' Command
-------------------------
Synopsis
........
-var-delete NAME
Deletes a previously created variable object and all of its children.
Returns an error if the object NAME is not found.
The `-var-set-format' Command
-----------------------------
Synopsis
........
-var-set-format NAME FORMAT-SPEC
Sets the output format for the value of the object NAME to be
FORMAT-SPEC.
The syntax for the FORMAT-SPEC is as follows:
FORMAT-SPEC ==>
{binary | decimal | hexadecimal | octal | natural}
The `-var-show-format' Command
------------------------------
Synopsis
........
-var-show-format NAME
Returns the format used to display the value of the object NAME.
FORMAT ==>
FORMAT-SPEC
The `-var-info-num-children' Command
------------------------------------
Synopsis
........
-var-info-num-children NAME
Returns the number of children of a variable object NAME:
numchild=N
The `-var-list-children' Command
--------------------------------
Synopsis
........
-var-list-children [PRINT-VALUES] NAME
Return a list of the children of the specified variable object and
create variable objects for them, if they do not already exist. With a
single argument or if PRINT-VALUES has a value for of 0 or
`--no-values', print only the names of the variables; if PRINT-VALUES
is 1 or `--all-values', also print their values; and if it is 2 or
`--simple-values' print the name and value for simple data types and
just the name for arrays, structures and unions.
Example
.......
(gdb)
-var-list-children n
^done,numchild=N,children=[{name=NAME,
numchild=N,type=TYPE},(repeats N times)]
(gdb)
-var-list-children --all-values n
^done,numchild=N,children=[{name=NAME,
numchild=N,value=VALUE,type=TYPE},(repeats N times)]
The `-var-info-type' Command
----------------------------
Synopsis
........
-var-info-type NAME
Returns the type of the specified variable NAME. The type is
returned as a string in the same format as it is output by the GDB CLI:
type=TYPENAME
The `-var-info-expression' Command
----------------------------------
Synopsis
........
-var-info-expression NAME
Returns what is represented by the variable object NAME:
lang=LANG-SPEC,exp=EXPRESSION
where LANG-SPEC is `{"C" | "C++" | "Java"}'.
The `-var-show-attributes' Command
----------------------------------
Synopsis
........
-var-show-attributes NAME
List attributes of the specified variable object NAME:
status=ATTR [ ( ,ATTR )* ]
where ATTR is `{ { editable | noneditable } | TBD }'.
The `-var-evaluate-expression' Command
--------------------------------------
Synopsis
........
-var-evaluate-expression NAME
Evaluates the expression that is represented by the specified
variable object and returns its value as a string in the current format
specified for the object:
value=VALUE
Note that one must invoke `-var-list-children' for a variable before
the value of a child variable can be evaluated.
The `-var-assign' Command
-------------------------
Synopsis
........
-var-assign NAME EXPRESSION
Assigns the value of EXPRESSION to the variable object specified by
NAME. The object must be `editable'. If the variable's value is
altered by the assign, the variable will show up in any subsequent
`-var-update' list.
Example
.......
(gdb)
-var-assign var1 3
^done,value="3"
(gdb)
-var-update *
^done,changelist=[{name="var1",in_scope="true",type_changed="false"}]
(gdb)
The `-var-update' Command
-------------------------
Synopsis
........
-var-update [PRINT-VALUES] {NAME | "*"}
Update the value of the variable object NAME by evaluating its
expression after fetching all the new values from memory or registers.
A `*' causes all existing variable objects to be updated. The option
PRINT-VALUES determines whether names both and values, or just names
are printed in the manner described for `-var-list-children' (*note
-var-list-children::).
Example
.......
(gdb)
-var-assign var1 3
^done,value="3"
(gdb)
-var-update --all-values var1
^done,changelist=[{name="var1",value="3",in_scope="true",
type_changed="false"}]
(gdb)

File: gdb.info, Node: GDB/MI Data Manipulation, Next: GDB/MI Tracepoint Commands, Prev: GDB/MI Variable Objects, Up: GDB/MI
24.13 GDB/MI Data Manipulation
==============================
This section describes the GDB/MI commands that manipulate data:
examine memory and registers, evaluate expressions, etc.
The `-data-disassemble' Command
-------------------------------
Synopsis
........
-data-disassemble
[ -s START-ADDR -e END-ADDR ]
| [ -f FILENAME -l LINENUM [ -n LINES ] ]
-- MODE
Where:
`START-ADDR'
is the beginning address (or `$pc')
`END-ADDR'
is the end address
`FILENAME'
is the name of the file to disassemble
`LINENUM'
is the line number to disassemble around
`LINES'
is the the number of disassembly lines to be produced. If it is
-1, the whole function will be disassembled, in case no END-ADDR is
specified. If END-ADDR is specified as a non-zero value, and
LINES is lower than the number of disassembly lines between
START-ADDR and END-ADDR, only LINES lines are displayed; if LINES
is higher than the number of lines between START-ADDR and
END-ADDR, only the lines up to END-ADDR are displayed.
`MODE'
is either 0 (meaning only disassembly) or 1 (meaning mixed source
and disassembly).
Result
......
The output for each instruction is composed of four fields:
* Address
* Func-name
* Offset
* Instruction
Note that whatever included in the instruction field, is not
manipulated directely by GDB/MI, i.e. it is not possible to adjust its
format.
GDB Command
...........
There's no direct mapping from this command to the CLI.
Example
.......
Disassemble from the current value of `$pc' to `$pc + 20':
(gdb)
-data-disassemble -s $pc -e "$pc + 20" -- 0
^done,
asm_insns=[
{address="0x000107c0",func-name="main",offset="4",
inst="mov 2, %o0"},
{address="0x000107c4",func-name="main",offset="8",
inst="sethi %hi(0x11800), %o2"},
{address="0x000107c8",func-name="main",offset="12",
inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"},
{address="0x000107cc",func-name="main",offset="16",
inst="sethi %hi(0x11800), %o2"},
{address="0x000107d0",func-name="main",offset="20",
inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"}]
(gdb)
Disassemble the whole `main' function. Line 32 is part of `main'.
-data-disassemble -f basics.c -l 32 -- 0
^done,asm_insns=[
{address="0x000107bc",func-name="main",offset="0",
inst="save %sp, -112, %sp"},
{address="0x000107c0",func-name="main",offset="4",
inst="mov 2, %o0"},
{address="0x000107c4",func-name="main",offset="8",
inst="sethi %hi(0x11800), %o2"},
[...]
{address="0x0001081c",func-name="main",offset="96",inst="ret "},
{address="0x00010820",func-name="main",offset="100",inst="restore "}]
(gdb)
Disassemble 3 instructions from the start of `main':
(gdb)
-data-disassemble -f basics.c -l 32 -n 3 -- 0
^done,asm_insns=[
{address="0x000107bc",func-name="main",offset="0",
inst="save %sp, -112, %sp"},
{address="0x000107c0",func-name="main",offset="4",
inst="mov 2, %o0"},
{address="0x000107c4",func-name="main",offset="8",
inst="sethi %hi(0x11800), %o2"}]
(gdb)
Disassemble 3 instructions from the start of `main' in mixed mode:
(gdb)
-data-disassemble -f basics.c -l 32 -n 3 -- 1
^done,asm_insns=[
src_and_asm_line={line="31",
file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
testsuite/gdb.mi/basics.c",line_asm_insn=[
{address="0x000107bc",func-name="main",offset="0",
inst="save %sp, -112, %sp"}]},
src_and_asm_line={line="32",
file="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb/ \
testsuite/gdb.mi/basics.c",line_asm_insn=[
{address="0x000107c0",func-name="main",offset="4",
inst="mov 2, %o0"},
{address="0x000107c4",func-name="main",offset="8",
inst="sethi %hi(0x11800), %o2"}]}]
(gdb)
The `-data-evaluate-expression' Command
---------------------------------------
Synopsis
........
-data-evaluate-expression EXPR
Evaluate EXPR as an expression. The expression could contain an
inferior function call. The function call will execute synchronously.
If the expression contains spaces, it must be enclosed in double quotes.
GDB Command
...........
The corresponding GDB commands are `print', `output', and `call'. In
`gdbtk' only, there's a corresponding `gdb_eval' command.
Example
.......
In the following example, the numbers that precede the commands are the
"tokens" described in *Note GDB/MI Command Syntax: GDB/MI Command
Syntax. Notice how GDB/MI returns the same tokens in its output.
211-data-evaluate-expression A
211^done,value="1"
(gdb)
311-data-evaluate-expression &A
311^done,value="0xefffeb7c"
(gdb)
411-data-evaluate-expression A+3
411^done,value="4"
(gdb)
511-data-evaluate-expression "A + 3"
511^done,value="4"
(gdb)
The `-data-list-changed-registers' Command
------------------------------------------
Synopsis
........
-data-list-changed-registers
Display a list of the registers that have changed.
GDB Command
...........
GDB doesn't have a direct analog for this command; `gdbtk' has the
corresponding command `gdb_changed_register_list'.
Example
.......
On a PPC MBX board:
(gdb)
-exec-continue
^running
(gdb)
*stopped,reason="breakpoint-hit",bkptno="1",frame={func="main",
args=[],file="try.c",fullname="/home/foo/bar/try.c",line="5"}
(gdb)
-data-list-changed-registers
^done,changed-registers=["0","1","2","4","5","6","7","8","9",
"10","11","13","14","15","16","17","18","19","20","21","22","23",
"24","25","26","27","28","30","31","64","65","66","67","69"]
(gdb)
The `-data-list-register-names' Command
---------------------------------------
Synopsis
........
-data-list-register-names [ ( REGNO )+ ]
Show a list of register names for the current target. If no
arguments are given, it shows a list of the names of all the registers.
If integer numbers are given as arguments, it will print a list of the
names of the registers corresponding to the arguments. To ensure
consistency between a register name and its number, the output list may
include empty register names.
GDB Command
...........
GDB does not have a command which corresponds to
`-data-list-register-names'. In `gdbtk' there is a corresponding
command `gdb_regnames'.
Example
.......
For the PPC MBX board:
(gdb)
-data-list-register-names
^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
"r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
"r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
"r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
"f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
"f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
"", "pc","ps","cr","lr","ctr","xer"]
(gdb)
-data-list-register-names 1 2 3
^done,register-names=["r1","r2","r3"]
(gdb)
The `-data-list-register-values' Command
----------------------------------------
Synopsis
........
-data-list-register-values FMT [ ( REGNO )*]
Display the registers' contents. FMT is the format according to
which the registers' contents are to be returned, followed by an
optional list of numbers specifying the registers to display. A
missing list of numbers indicates that the contents of all the
registers must be returned.
Allowed formats for FMT are:
`x'
Hexadecimal
`o'
Octal
`t'
Binary
`d'
Decimal
`r'
Raw
`N'
Natural
GDB Command
...........
The corresponding GDB commands are `info reg', `info all-reg', and (in
`gdbtk') `gdb_fetch_registers'.
Example
.......
For a PPC MBX board (note: line breaks are for readability only, they
don't appear in the actual output):
(gdb)
-data-list-register-values r 64 65
^done,register-values=[{number="64",value="0xfe00a300"},
{number="65",value="0x00029002"}]
(gdb)
-data-list-register-values x
^done,register-values=[{number="0",value="0xfe0043c8"},
{number="1",value="0x3fff88"},{number="2",value="0xfffffffe"},
{number="3",value="0x0"},{number="4",value="0xa"},
{number="5",value="0x3fff68"},{number="6",value="0x3fff58"},
{number="7",value="0xfe011e98"},{number="8",value="0x2"},
{number="9",value="0xfa202820"},{number="10",value="0xfa202808"},
{number="11",value="0x1"},{number="12",value="0x0"},
{number="13",value="0x4544"},{number="14",value="0xffdfffff"},
{number="15",value="0xffffffff"},{number="16",value="0xfffffeff"},
{number="17",value="0xefffffed"},{number="18",value="0xfffffffe"},
{number="19",value="0xffffffff"},{number="20",value="0xffffffff"},
{number="21",value="0xffffffff"},{number="22",value="0xfffffff7"},
{number="23",value="0xffffffff"},{number="24",value="0xffffffff"},
{number="25",value="0xffffffff"},{number="26",value="0xfffffffb"},
{number="27",value="0xffffffff"},{number="28",value="0xf7bfffff"},
{number="29",value="0x0"},{number="30",value="0xfe010000"},
{number="31",value="0x0"},{number="32",value="0x0"},
{number="33",value="0x0"},{number="34",value="0x0"},
{number="35",value="0x0"},{number="36",value="0x0"},
{number="37",value="0x0"},{number="38",value="0x0"},
{number="39",value="0x0"},{number="40",value="0x0"},
{number="41",value="0x0"},{number="42",value="0x0"},
{number="43",value="0x0"},{number="44",value="0x0"},
{number="45",value="0x0"},{number="46",value="0x0"},
{number="47",value="0x0"},{number="48",value="0x0"},
{number="49",value="0x0"},{number="50",value="0x0"},
{number="51",value="0x0"},{number="52",value="0x0"},
{number="53",value="0x0"},{number="54",value="0x0"},
{number="55",value="0x0"},{number="56",value="0x0"},
{number="57",value="0x0"},{number="58",value="0x0"},
{number="59",value="0x0"},{number="60",value="0x0"},
{number="61",value="0x0"},{number="62",value="0x0"},
{number="63",value="0x0"},{number="64",value="0xfe00a300"},
{number="65",value="0x29002"},{number="66",value="0x202f04b5"},
{number="67",value="0xfe0043b0"},{number="68",value="0xfe00b3e4"},
{number="69",value="0x20002b03"}]
(gdb)
The `-data-read-memory' Command
-------------------------------
Synopsis
........
-data-read-memory [ -o BYTE-OFFSET ]
ADDRESS WORD-FORMAT WORD-SIZE
NR-ROWS NR-COLS [ ASCHAR ]
where:
`ADDRESS'
An expression specifying the address of the first memory word to be
read. Complex expressions containing embedded white space should
be quoted using the C convention.
`WORD-FORMAT'
The format to be used to print the memory words. The notation is
the same as for GDB's `print' command (*note Output formats:
Output Formats.).
`WORD-SIZE'
The size of each memory word in bytes.
`NR-ROWS'
The number of rows in the output table.
`NR-COLS'
The number of columns in the output table.
`ASCHAR'
If present, indicates that each row should include an ASCII dump.
The value of ASCHAR is used as a padding character when a byte is
not a member of the printable ASCII character set (printable ASCII
characters are those whose code is between 32 and 126,
inclusively).
`BYTE-OFFSET'
An offset to add to the ADDRESS before fetching memory.
This command displays memory contents as a table of NR-ROWS by
NR-COLS words, each word being WORD-SIZE bytes. In total, `NR-ROWS *
NR-COLS * WORD-SIZE' bytes are read (returned as `total-bytes').
Should less than the requested number of bytes be returned by the
target, the missing words are identified using `N/A'. The number of
bytes read from the target is returned in `nr-bytes' and the starting
address used to read memory in `addr'.
The address of the next/previous row or page is available in
`next-row' and `prev-row', `next-page' and `prev-page'.
GDB Command
...........
The corresponding GDB command is `x'. `gdbtk' has `gdb_get_mem' memory
read command.
Example
.......
Read six bytes of memory starting at `bytes+6' but then offset by `-6'
bytes. Format as three rows of two columns. One byte per word.
Display each word in hex.
(gdb)
9-data-read-memory -o -6 -- bytes+6 x 1 3 2
9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
prev-page="0x0000138a",memory=[
{addr="0x00001390",data=["0x00","0x01"]},
{addr="0x00001392",data=["0x02","0x03"]},
{addr="0x00001394",data=["0x04","0x05"]}]
(gdb)
Read two bytes of memory starting at address `shorts + 64' and
display as a single word formatted in decimal.
(gdb)
5-data-read-memory shorts+64 d 2 1 1
5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
next-row="0x00001512",prev-row="0x0000150e",
next-page="0x00001512",prev-page="0x0000150e",memory=[
{addr="0x00001510",data=["128"]}]
(gdb)
Read thirty two bytes of memory starting at `bytes+16' and format as
eight rows of four columns. Include a string encoding with `x' used as
the non-printable character.
(gdb)
4-data-read-memory bytes+16 x 1 8 4 x
4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
next-row="0x000013c0",prev-row="0x0000139c",
next-page="0x000013c0",prev-page="0x00001380",memory=[
{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"},
{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"},
{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"},
{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"},
{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"},
{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"},
{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"},
{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"}]
(gdb)

File: gdb.info, Node: GDB/MI Tracepoint Commands, Next: GDB/MI Symbol Query, Prev: GDB/MI Data Manipulation, Up: GDB/MI
24.14 GDB/MI Tracepoint Commands
================================
The tracepoint commands are not yet implemented.

File: gdb.info, Node: GDB/MI Symbol Query, Next: GDB/MI File Commands, Prev: GDB/MI Tracepoint Commands, Up: GDB/MI
24.15 GDB/MI Symbol Query Commands
==================================
The `-symbol-info-address' Command
----------------------------------
Synopsis
........
-symbol-info-address SYMBOL
Describe where SYMBOL is stored.
GDB Command
...........
The corresponding GDB command is `info address'.
Example
.......
N.A.
The `-symbol-info-file' Command
-------------------------------
Synopsis
........
-symbol-info-file
Show the file for the symbol.
GDB Command
...........
There's no equivalent GDB command. `gdbtk' has `gdb_find_file'.
Example
.......
N.A.
The `-symbol-info-function' Command
-----------------------------------
Synopsis
........
-symbol-info-function
Show which function the symbol lives in.
GDB Command
...........
`gdb_get_function' in `gdbtk'.
Example
.......
N.A.
The `-symbol-info-line' Command
-------------------------------
Synopsis
........
-symbol-info-line
Show the core addresses of the code for a source line.
GDB Command
...........
The corresponding GDB command is `info line'. `gdbtk' has the
`gdb_get_line' and `gdb_get_file' commands.
Example
.......
N.A.
The `-symbol-info-symbol' Command
---------------------------------
Synopsis
........
-symbol-info-symbol ADDR
Describe what symbol is at location ADDR.
GDB Command
...........
The corresponding GDB command is `info symbol'.
Example
.......
N.A.
The `-symbol-list-functions' Command
------------------------------------
Synopsis
........
-symbol-list-functions
List the functions in the executable.
GDB Command
...........
`info functions' in GDB, `gdb_listfunc' and `gdb_search' in `gdbtk'.
Example
.......
N.A.
The `-symbol-list-lines' Command
--------------------------------
Synopsis
........
-symbol-list-lines FILENAME
Print the list of lines that contain code and their associated
program addresses for the given source filename. The entries are
sorted in ascending PC order.
GDB Command
...........
There is no corresponding GDB command.
Example
.......
(gdb)
-symbol-list-lines basics.c
^done,lines=[{pc="0x08048554",line="7"},{pc="0x0804855a",line="8"}]
(gdb)
The `-symbol-list-types' Command
--------------------------------
Synopsis
........
-symbol-list-types
List all the type names.
GDB Command
...........
The corresponding commands are `info types' in GDB, `gdb_search' in
`gdbtk'.
Example
.......
N.A.
The `-symbol-list-variables' Command
------------------------------------
Synopsis
........
-symbol-list-variables
List all the global and static variable names.
GDB Command
...........
`info variables' in GDB, `gdb_search' in `gdbtk'.
Example
.......
N.A.
The `-symbol-locate' Command
----------------------------
Synopsis
........
-symbol-locate
GDB Command
...........
`gdb_loc' in `gdbtk'.
Example
.......
N.A.
The `-symbol-type' Command
--------------------------
Synopsis
........
-symbol-type VARIABLE
Show type of VARIABLE.
GDB Command
...........
The corresponding GDB command is `ptype', `gdbtk' has
`gdb_obj_variable'.
Example
.......
N.A.

File: gdb.info, Node: GDB/MI File Commands, Next: GDB/MI Target Manipulation, Prev: GDB/MI Symbol Query, Up: GDB/MI
24.16 GDB/MI File Commands
==========================
This section describes the GDB/MI commands to specify executable file
names and to read in and obtain symbol table information.
The `-file-exec-and-symbols' Command
------------------------------------
Synopsis
........
-file-exec-and-symbols FILE
Specify the executable file to be debugged. This file is the one
from which the symbol table is also read. If no file is specified, the
command clears the executable and symbol information. If breakpoints
are set when using this command with no arguments, GDB will produce
error messages. Otherwise, no output is produced, except a completion
notification.
GDB Command
...........
The corresponding GDB command is `file'.
Example
.......
(gdb)
-file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
^done
(gdb)
The `-file-exec-file' Command
-----------------------------
Synopsis
........
-file-exec-file FILE
Specify the executable file to be debugged. Unlike
`-file-exec-and-symbols', the symbol table is _not_ read from this
file. If used without argument, GDB clears the information about the
executable file. No output is produced, except a completion
notification.
GDB Command
...........
The corresponding GDB command is `exec-file'.
Example
.......
(gdb)
-file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
^done
(gdb)
The `-file-list-exec-sections' Command
--------------------------------------
Synopsis
........
-file-list-exec-sections
List the sections of the current executable file.
GDB Command
...........
The GDB command `info file' shows, among the rest, the same information
as this command. `gdbtk' has a corresponding command `gdb_load_info'.
Example
.......
N.A.
The `-file-list-exec-source-file' Command
-----------------------------------------
Synopsis
........
-file-list-exec-source-file
List the line number, the current source file, and the absolute path
to the current source file for the current executable.
GDB Command
...........
The GDB equivalent is `info source'
Example
.......
(gdb)
123-file-list-exec-source-file
123^done,line="1",file="foo.c",fullname="/home/bar/foo.c"
(gdb)
The `-file-list-exec-source-files' Command
------------------------------------------
Synopsis
........
-file-list-exec-source-files
List the source files for the current executable.
It will always output the filename, but only when GDB can find the
absolute file name of a source file, will it output the fullname.
GDB Command
...........
The GDB equivalent is `info sources'. `gdbtk' has an analogous command
`gdb_listfiles'.
Example
.......
(gdb)
-file-list-exec-source-files
^done,files=[
{file=foo.c,fullname=/home/foo.c},
{file=/home/bar.c,fullname=/home/bar.c},
{file=gdb_could_not_find_fullpath.c}]
(gdb)
The `-file-list-shared-libraries' Command
-----------------------------------------
Synopsis
........
-file-list-shared-libraries
List the shared libraries in the program.
GDB Command
...........
The corresponding GDB command is `info shared'.
Example
.......
N.A.
The `-file-list-symbol-files' Command
-------------------------------------
Synopsis
........
-file-list-symbol-files
List symbol files.
GDB Command
...........
The corresponding GDB command is `info file' (part of it).
Example
.......
N.A.
The `-file-symbol-file' Command
-------------------------------
Synopsis
........
-file-symbol-file FILE
Read symbol table info from the specified FILE argument. When used
without arguments, clears GDB's symbol table info. No output is
produced, except for a completion notification.
GDB Command
...........
The corresponding GDB command is `symbol-file'.
Example
.......
(gdb)
-file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
^done
(gdb)

File: gdb.info, Node: GDB/MI Target Manipulation, Next: GDB/MI Miscellaneous Commands, Prev: GDB/MI File Commands, Up: GDB/MI
24.17 GDB/MI Target Manipulation Commands
=========================================
The `-target-attach' Command
----------------------------
Synopsis
........
-target-attach PID | FILE
Attach to a process PID or a file FILE outside of GDB.
GDB command
...........
The corresponding GDB command is `attach'.
Example
.......
N.A.
The `-target-compare-sections' Command
--------------------------------------
Synopsis
........
-target-compare-sections [ SECTION ]
Compare data of section SECTION on target to the exec file. Without
the argument, all sections are compared.
GDB Command
...........
The GDB equivalent is `compare-sections'.
Example
.......
N.A.
The `-target-detach' Command
----------------------------
Synopsis
........
-target-detach
Detach from the remote target which normally resumes its execution.
There's no output.
GDB command
...........
The corresponding GDB command is `detach'.
Example
.......
(gdb)
-target-detach
^done
(gdb)
The `-target-disconnect' Command
--------------------------------
Synopsis
........
-target-disconnect
Disconnect from the remote target. There's no output and the target
is generally not resumed.
GDB command
...........
The corresponding GDB command is `disconnect'.
Example
.......
(gdb)
-target-disconnect
^done
(gdb)
The `-target-download' Command
------------------------------
Synopsis
........
-target-download
Loads the executable onto the remote target. It prints out an
update message every half second, which includes the fields:
`section'
The name of the section.
`section-sent'
The size of what has been sent so far for that section.
`section-size'
The size of the section.
`total-sent'
The total size of what was sent so far (the current and the
previous sections).
`total-size'
The size of the overall executable to download.
Each message is sent as status record (*note GDB/MI Output Syntax:
GDB/MI Output Syntax.).
In addition, it prints the name and size of the sections, as they are
downloaded. These messages include the following fields:
`section'
The name of the section.
`section-size'
The size of the section.
`total-size'
The size of the overall executable to download.
At the end, a summary is printed.
GDB Command
...........
The corresponding GDB command is `load'.
Example
.......
Note: each status message appears on a single line. Here the messages
have been broken down so that they can fit onto a page.
(gdb)
-target-download
+download,{section=".text",section-size="6668",total-size="9880"}
+download,{section=".text",section-sent="512",section-size="6668",
total-sent="512",total-size="9880"}
+download,{section=".text",section-sent="1024",section-size="6668",
total-sent="1024",total-size="9880"}
+download,{section=".text",section-sent="1536",section-size="6668",
total-sent="1536",total-size="9880"}
+download,{section=".text",section-sent="2048",section-size="6668",
total-sent="2048",total-size="9880"}
+download,{section=".text",section-sent="2560",section-size="6668",
total-sent="2560",total-size="9880"}
+download,{section=".text",section-sent="3072",section-size="6668",
total-sent="3072",total-size="9880"}
+download,{section=".text",section-sent="3584",section-size="6668",
total-sent="3584",total-size="9880"}
+download,{section=".text",section-sent="4096",section-size="6668",
total-sent="4096",total-size="9880"}
+download,{section=".text",section-sent="4608",section-size="6668",
total-sent="4608",total-size="9880"}
+download,{section=".text",section-sent="5120",section-size="6668",
total-sent="5120",total-size="9880"}
+download,{section=".text",section-sent="5632",section-size="6668",
total-sent="5632",total-size="9880"}
+download,{section=".text",section-sent="6144",section-size="6668",
total-sent="6144",total-size="9880"}
+download,{section=".text",section-sent="6656",section-size="6668",
total-sent="6656",total-size="9880"}
+download,{section=".init",section-size="28",total-size="9880"}
+download,{section=".fini",section-size="28",total-size="9880"}
+download,{section=".data",section-size="3156",total-size="9880"}
+download,{section=".data",section-sent="512",section-size="3156",
total-sent="7236",total-size="9880"}
+download,{section=".data",section-sent="1024",section-size="3156",
total-sent="7748",total-size="9880"}
+download,{section=".data",section-sent="1536",section-size="3156",
total-sent="8260",total-size="9880"}
+download,{section=".data",section-sent="2048",section-size="3156",
total-sent="8772",total-size="9880"}
+download,{section=".data",section-sent="2560",section-size="3156",
total-sent="9284",total-size="9880"}
+download,{section=".data",section-sent="3072",section-size="3156",
total-sent="9796",total-size="9880"}
^done,address="0x10004",load-size="9880",transfer-rate="6586",
write-rate="429"
(gdb)
The `-target-exec-status' Command
---------------------------------
Synopsis
........
-target-exec-status
Provide information on the state of the target (whether it is
running or not, for instance).
GDB Command
...........
There's no equivalent GDB command.
Example
.......
N.A.
The `-target-list-available-targets' Command
--------------------------------------------
Synopsis
........
-target-list-available-targets
List the possible targets to connect to.
GDB Command
...........
The corresponding GDB command is `help target'.
Example
.......
N.A.
The `-target-list-current-targets' Command
------------------------------------------
Synopsis
........
-target-list-current-targets
Describe the current target.
GDB Command
...........
The corresponding information is printed by `info file' (among other
things).
Example
.......
N.A.
The `-target-list-parameters' Command
-------------------------------------
Synopsis
........
-target-list-parameters
GDB Command
...........
No equivalent.
Example
.......
N.A.
The `-target-select' Command
----------------------------
Synopsis
........
-target-select TYPE PARAMETERS ...
Connect GDB to the remote target. This command takes two args:
`TYPE'
The type of target, for instance `async', `remote', etc.
`PARAMETERS'
Device names, host names and the like. *Note Commands for
managing targets: Target Commands, for more details.
The output is a connection notification, followed by the address at
which the target program is, in the following form:
^connected,addr="ADDRESS",func="FUNCTION NAME",
args=[ARG LIST]
GDB Command
...........
The corresponding GDB command is `target'.
Example
.......
(gdb)
-target-select async /dev/ttya
^connected,addr="0xfe00a300",func="??",args=[]
(gdb)

File: gdb.info, Node: GDB/MI Miscellaneous Commands, Prev: GDB/MI Target Manipulation, Up: GDB/MI
24.18 Miscellaneous GDB/MI Commands
===================================
The `-gdb-exit' Command
-----------------------
Synopsis
........
-gdb-exit
Exit GDB immediately.
GDB Command
...........
Approximately corresponds to `quit'.
Example
.......
(gdb)
-gdb-exit
^exit
The `-exec-abort' Command
-------------------------
Synopsis
........
-exec-abort
Kill the inferior running program.
GDB Command
...........
The corresponding GDB command is `kill'.
Example
.......
N.A.
The `-gdb-set' Command
----------------------
Synopsis
........
-gdb-set
Set an internal GDB variable.
GDB Command
...........
The corresponding GDB command is `set'.
Example
.......
(gdb)
-gdb-set $foo=3
^done
(gdb)
The `-gdb-show' Command
-----------------------
Synopsis
........
-gdb-show
Show the current value of a GDB variable.
GDB command
...........
The corresponding GDB command is `show'.
Example
.......
(gdb)
-gdb-show annotate
^done,value="0"
(gdb)
The `-gdb-version' Command
--------------------------
Synopsis
........
-gdb-version
Show version information for GDB. Used mostly in testing.
GDB Command
...........
The GDB equivalent is `show version'. GDB by default shows this
information when you start an interactive session.
Example
.......
(gdb)
-gdb-version
~GNU gdb 5.2.1
~Copyright 2000 Free Software Foundation, Inc.
~GDB is free software, covered by the GNU General Public License, and
~you are welcome to change it and/or distribute copies of it under
~ certain conditions.
~Type "show copying" to see the conditions.
~There is absolutely no warranty for GDB. Type "show warranty" for
~ details.
~This GDB was configured as
"--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
^done
(gdb)
The `-interpreter-exec' Command
-------------------------------
Synopsis
--------
-interpreter-exec INTERPRETER COMMAND
Execute the specified COMMAND in the given INTERPRETER.
GDB Command
-----------
The corresponding GDB command is `interpreter-exec'.
Example
-------
(gdb)
-interpreter-exec console "break main"
&"During symbol reading, couldn't parse type; debugger out of date?.\n"
&"During symbol reading, bad structure-type format.\n"
~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
^done
(gdb)
The `-inferior-tty-set' Command
-------------------------------
Synopsis
--------
-inferior-tty-set /dev/pts/1
Set terminal for future runs of the program being debugged.
GDB Command
-----------
The corresponding GDB command is `set inferior-tty' /dev/pts/1.
Example
-------
(gdb)
-inferior-tty-set /dev/pts/1
^done
(gdb)
The `-inferior-tty-show' Command
--------------------------------
Synopsis
--------
-inferior-tty-show
Show terminal for future runs of program being debugged.
GDB Command
-----------
The corresponding GDB command is `show inferior-tty'.
Example
-------
(gdb)
-inferior-tty-set /dev/pts/1
^done
(gdb)
-inferior-tty-show
^done,inferior_tty_terminal="/dev/pts/1"
(gdb)

File: gdb.info, Node: Annotations, Next: GDB/MI, Prev: Emacs, Up: Top
25 GDB Annotations
******************
This chapter describes annotations in GDB. Annotations were designed
to interface GDB to graphical user interfaces or other similar programs
which want to interact with GDB at a relatively high level.
The annotation mechanism has largely been superseeded by GDB/MI
(*note GDB/MI::).
* Menu:
* Annotations Overview:: What annotations are; the general syntax.
* Prompting:: Annotations marking GDB's need for input.
* Errors:: Annotations for error messages.
* Invalidation:: Some annotations describe things now invalid.
* Annotations for Running::
Whether the program is running, how it stopped, etc.
* Source Annotations:: Annotations describing source code.

File: gdb.info, Node: Annotations Overview, Next: Prompting, Up: Annotations
25.1 What is an Annotation?
===========================
Annotations start with a newline character, two `control-z' characters,
and the name of the annotation. If there is no additional information
associated with this annotation, the name of the annotation is followed
immediately by a newline. If there is additional information, the name
of the annotation is followed by a space, the additional information,
and a newline. The additional information cannot contain newline
characters.
Any output not beginning with a newline and two `control-z'
characters denotes literal output from GDB. Currently there is no need
for GDB to output a newline followed by two `control-z' characters, but
if there was such a need, the annotations could be extended with an
`escape' annotation which means those three characters as output.
The annotation LEVEL, which is specified using the `--annotate'
command line option (*note Mode Options::), controls how much
information GDB prints together with its prompt, values of expressions,
source lines, and other types of output. Level 0 is for no anntations,
level 1 is for use when GDB is run as a subprocess of GNU Emacs, level
3 is the maximum annotation suitable for programs that control GDB, and
level 2 annotations have been made obsolete (*note Limitations of the
Annotation Interface: (annotate)Limitations.).
`set annotate LEVEL'
The GDB command `set annotate' sets the level of annotations to
the specified LEVEL.
`show annotate'
Show the current annotation level.
This chapter describes level 3 annotations.
A simple example of starting up GDB with annotations is:
$ gdb --annotate=3
GNU gdb 6.0
Copyright 2003 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License,
and you are welcome to change it and/or distribute copies of it
under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB. Type "show warranty"
for details.
This GDB was configured as "i386-pc-linux-gnu"
^Z^Zpre-prompt
(gdb)
^Z^Zprompt
quit
^Z^Zpost-prompt
$
Here `quit' is input to GDB; the rest is output from GDB. The three
lines beginning `^Z^Z' (where `^Z' denotes a `control-z' character) are
annotations; the rest is output from GDB.

File: gdb.info, Node: Prompting, Next: Errors, Prev: Annotations Overview, Up: Annotations
25.2 Annotation for GDB Input
=============================
When GDB prompts for input, it annotates this fact so it is possible to
know when to send output, when the output from a given command is over,
etc.
Different kinds of input each have a different "input type". Each
input type has three annotations: a `pre-' annotation, which denotes
the beginning of any prompt which is being output, a plain annotation,
which denotes the end of the prompt, and then a `post-' annotation
which denotes the end of any echo which may (or may not) be associated
with the input. For example, the `prompt' input type features the
following annotations:
^Z^Zpre-prompt
^Z^Zprompt
^Z^Zpost-prompt
The input types are
`prompt'
When GDB is prompting for a command (the main GDB prompt).
`commands'
When GDB prompts for a set of commands, like in the `commands'
command. The annotations are repeated for each command which is
input.
`overload-choice'
When GDB wants the user to select between various overloaded
functions.
`query'
When GDB wants the user to confirm a potentially dangerous
operation.
`prompt-for-continue'
When GDB is asking the user to press return to continue. Note:
Don't expect this to work well; instead use `set height 0' to
disable prompting. This is because the counting of lines is buggy
in the presence of annotations.

File: gdb.info, Node: Errors, Next: Invalidation, Prev: Prompting, Up: Annotations
25.3 Errors
===========
^Z^Zquit
This annotation occurs right before GDB responds to an interrupt.
^Z^Zerror
This annotation occurs right before GDB responds to an error.
Quit and error annotations indicate that any annotations which GDB
was in the middle of may end abruptly. For example, if a
`value-history-begin' annotation is followed by a `error', one cannot
expect to receive the matching `value-history-end'. One cannot expect
not to receive it either, however; an error annotation does not
necessarily mean that GDB is immediately returning all the way to the
top level.
A quit or error annotation may be preceded by
^Z^Zerror-begin
Any output between that and the quit or error annotation is the error
message.
Warning messages are not yet annotated.

File: gdb.info, Node: Invalidation, Next: Annotations for Running, Prev: Errors, Up: Annotations
25.4 Invalidation Notices
=========================
The following annotations say that certain pieces of state may have
changed.
`^Z^Zframes-invalid'
The frames (for example, output from the `backtrace' command) may
have changed.
`^Z^Zbreakpoints-invalid'
The breakpoints may have changed. For example, the user just
added or deleted a breakpoint.

File: gdb.info, Node: Annotations for Running, Next: Source Annotations, Prev: Invalidation, Up: Annotations
25.5 Running the Program
========================
When the program starts executing due to a GDB command such as `step'
or `continue',
^Z^Zstarting
is output. When the program stops,
^Z^Zstopped
is output. Before the `stopped' annotation, a variety of
annotations describe how the program stopped.
`^Z^Zexited EXIT-STATUS'
The program exited, and EXIT-STATUS is the exit status (zero for
successful exit, otherwise nonzero).
`^Z^Zsignalled'
The program exited with a signal. After the `^Z^Zsignalled', the
annotation continues:
INTRO-TEXT
^Z^Zsignal-name
NAME
^Z^Zsignal-name-end
MIDDLE-TEXT
^Z^Zsignal-string
STRING
^Z^Zsignal-string-end
END-TEXT
where NAME is the name of the signal, such as `SIGILL' or
`SIGSEGV', and STRING is the explanation of the signal, such as
`Illegal Instruction' or `Segmentation fault'. INTRO-TEXT,
MIDDLE-TEXT, and END-TEXT are for the user's benefit and have no
particular format.
`^Z^Zsignal'
The syntax of this annotation is just like `signalled', but GDB is
just saying that the program received the signal, not that it was
terminated with it.
`^Z^Zbreakpoint NUMBER'
The program hit breakpoint number NUMBER.
`^Z^Zwatchpoint NUMBER'
The program hit watchpoint number NUMBER.

File: gdb.info, Node: Source Annotations, Prev: Annotations for Running, Up: Annotations
25.6 Displaying Source
======================
The following annotation is used instead of displaying source code:
^Z^Zsource FILENAME:LINE:CHARACTER:MIDDLE:ADDR
where FILENAME is an absolute file name indicating which source
file, LINE is the line number within that file (where 1 is the first
line in the file), CHARACTER is the character position within the file
(where 0 is the first character in the file) (for most debug formats
this will necessarily point to the beginning of a line), MIDDLE is
`middle' if ADDR is in the middle of the line, or `beg' if ADDR is at
the beginning of the line, and ADDR is the address in the target
program associated with the source which is being displayed. ADDR is
in the form `0x' followed by one or more lowercase hex digits (note
that this does not depend on the language).

File: gdb.info, Node: GDB Bugs, Next: Formatting Documentation, Prev: GDB/MI, Up: Top
26 Reporting Bugs in GDB
************************
Your bug reports play an essential role in making GDB reliable.
Reporting a bug may help you by bringing a solution to your problem,
or it may not. But in any case the principal function of a bug report
is to help the entire community by making the next version of GDB work
better. Bug reports are your contribution to the maintenance of GDB.
In order for a bug report to serve its purpose, you must include the
information that enables us to fix the bug.
* Menu:
* Bug Criteria:: Have you found a bug?
* Bug Reporting:: How to report bugs

File: gdb.info, Node: Bug Criteria, Next: Bug Reporting, Up: GDB Bugs
26.1 Have you found a bug?
==========================
If you are not sure whether you have found a bug, here are some
guidelines:
* If the debugger gets a fatal signal, for any input whatever, that
is a GDB bug. Reliable debuggers never crash.
* If GDB produces an error message for valid input, that is a bug.
(Note that if you're cross debugging, the problem may also be
somewhere in the connection to the target.)
* If GDB does not produce an error message for invalid input, that
is a bug. However, you should note that your idea of "invalid
input" might be our idea of "an extension" or "support for
traditional practice".
* If you are an experienced user of debugging tools, your suggestions
for improvement of GDB are welcome in any case.

File: gdb.info, Node: Bug Reporting, Prev: Bug Criteria, Up: GDB Bugs
26.2 How to report bugs
=======================
A number of companies and individuals offer support for GNU products.
If you obtained GDB from a support organization, we recommend you
contact that organization first.
You can find contact information for many support companies and
individuals in the file `etc/SERVICE' in the GNU Emacs distribution.
In any event, we also recommend that you submit bug reports for GDB.
The prefered method is to submit them directly using GDB's Bugs web
page (http://www.gnu.org/software/gdb/bugs/). Alternatively, the
e-mail gateway <bug-gdb@gnu.org> can be used.
*Do not send bug reports to `info-gdb', or to `help-gdb', or to any
newsgroups.* Most users of GDB do not want to receive bug reports.
Those that do have arranged to receive `bug-gdb'.
The mailing list `bug-gdb' has a newsgroup `gnu.gdb.bug' which
serves as a repeater. The mailing list and the newsgroup carry exactly
the same messages. Often people think of posting bug reports to the
newsgroup instead of mailing them. This appears to work, but it has one
problem which can be crucial: a newsgroup posting often lacks a mail
path back to the sender. Thus, if we need to ask for more information,
we may be unable to reach you. For this reason, it is better to send
bug reports to the mailing list.
The fundamental principle of reporting bugs usefully is this:
*report all the facts*. If you are not sure whether to state a fact or
leave it out, state it!
Often people omit facts because they think they know what causes the
problem and assume that some details do not matter. Thus, you might
assume that the name of the variable you use in an example does not
matter. Well, probably it does not, but one cannot be sure. Perhaps
the bug is a stray memory reference which happens to fetch from the
location where that name is stored in memory; perhaps, if the name were
different, the contents of that location would fool the debugger into
doing the right thing despite the bug. Play it safe and give a
specific, complete example. That is the easiest thing for you to do,
and the most helpful.
Keep in mind that the purpose of a bug report is to enable us to fix
the bug. It may be that the bug has been reported previously, but
neither you nor we can know that unless your bug report is complete and
self-contained.
Sometimes people give a few sketchy facts and ask, "Does this ring a
bell?" Those bug reports are useless, and we urge everyone to _refuse
to respond to them_ except to chide the sender to report bugs properly.
To enable us to fix the bug, you should include all these things:
* The version of GDB. GDB announces it if you start with no
arguments; you can also print it at any time using `show version'.
Without this, we will not know whether there is any point in
looking for the bug in the current version of GDB.
* The type of machine you are using, and the operating system name
and version number.
* What compiler (and its version) was used to compile GDB--e.g.
"gcc-2.8.1".
* What compiler (and its version) was used to compile the program
you are debugging--e.g. "gcc-2.8.1", or "HP92453-01 A.10.32.03 HP
C Compiler". For GCC, you can say `gcc --version' to get this
information; for other compilers, see the documentation for those
compilers.
* The command arguments you gave the compiler to compile your
example and observe the bug. For example, did you use `-O'? To
guarantee you will not omit something important, list them all. A
copy of the Makefile (or the output from make) is sufficient.
If we were to try to guess the arguments, we would probably guess
wrong and then we might not encounter the bug.
* A complete input script, and all necessary source files, that will
reproduce the bug.
* A description of what behavior you observe that you believe is
incorrect. For example, "It gets a fatal signal."
Of course, if the bug is that GDB gets a fatal signal, then we
will certainly notice it. But if the bug is incorrect output, we
might not notice unless it is glaringly wrong. You might as well
not give us a chance to make a mistake.
Even if the problem you experience is a fatal signal, you should
still say so explicitly. Suppose something strange is going on,
such as, your copy of GDB is out of synch, or you have encountered
a bug in the C library on your system. (This has happened!) Your
copy might crash and ours would not. If you told us to expect a
crash, then when ours fails to crash, we would know that the bug
was not happening for us. If you had not told us to expect a
crash, then we would not be able to draw any conclusion from our
observations.
To collect all this information, you can use a session recording
program such as `script', which is available on many Unix systems.
Just run your GDB session inside `script' and then include the
`typescript' file with your bug report.
Another way to record a GDB session is to run GDB inside Emacs and
then save the entire buffer to a file.
* If you wish to suggest changes to the GDB source, send us context
diffs. If you even discuss something in the GDB source, refer to
it by context, not by line number.
The line numbers in our development sources will not match those
in your sources. Your line numbers would convey no useful
information to us.
Here are some things that are not necessary:
* A description of the envelope of the bug.
Often people who encounter a bug spend a lot of time investigating
which changes to the input file will make the bug go away and which
changes will not affect it.
This is often time consuming and not very useful, because the way
we will find the bug is by running a single example under the
debugger with breakpoints, not by pure deduction from a series of
examples. We recommend that you save your time for something else.
Of course, if you can find a simpler example to report _instead_
of the original one, that is a convenience for us. Errors in the
output will be easier to spot, running under the debugger will take
less time, and so on.
However, simplification is not vital; if you do not want to do
this, report the bug anyway and send us the entire test case you
used.
* A patch for the bug.
A patch for the bug does help us if it is a good one. But do not
omit the necessary information, such as the test case, on the
assumption that a patch is all we need. We might see problems
with your patch and decide to fix the problem another way, or we
might not understand it at all.
Sometimes with a program as complicated as GDB it is very hard to
construct an example that will make the program follow a certain
path through the code. If you do not send us the example, we will
not be able to construct one, so we will not be able to verify
that the bug is fixed.
And if we cannot understand what bug you are trying to fix, or why
your patch should be an improvement, we will not install it. A
test case will help us to understand.
* A guess about what the bug is or what it depends on.
Such guesses are usually wrong. Even we cannot guess right about
such things without first using the debugger to find the facts.

File: gdb.info, Node: Command Line Editing, Next: Using History Interactively, Prev: Formatting Documentation, Up: Top
27 Command Line Editing
***********************
This chapter describes the basic features of the GNU command line
editing interface.
* Menu:
* Introduction and Notation:: Notation used in this text.
* Readline Interaction:: The minimum set of commands for editing a line.
* Readline Init File:: Customizing Readline from a user's view.
* Bindable Readline Commands:: A description of most of the Readline commands
available for binding
* Readline vi Mode:: A short description of how to make Readline
behave like the vi editor.

File: gdb.info, Node: Introduction and Notation, Next: Readline Interaction, Up: Command Line Editing
27.1 Introduction to Line Editing
=================================
The following paragraphs describe the notation used to represent
keystrokes.
The text `C-k' is read as `Control-K' and describes the character
produced when the <k> key is pressed while the Control key is depressed.
The text `M-k' is read as `Meta-K' and describes the character
produced when the Meta key (if you have one) is depressed, and the <k>
key is pressed. The Meta key is labeled <ALT> on many keyboards. On
keyboards with two keys labeled <ALT> (usually to either side of the
space bar), the <ALT> on the left side is generally set to work as a
Meta key. The <ALT> key on the right may also be configured to work as
a Meta key or may be configured as some other modifier, such as a
Compose key for typing accented characters.
If you do not have a Meta or <ALT> key, or another key working as a
Meta key, the identical keystroke can be generated by typing <ESC>
_first_, and then typing <k>. Either process is known as "metafying"
the <k> key.
The text `M-C-k' is read as `Meta-Control-k' and describes the
character produced by "metafying" `C-k'.
In addition, several keys have their own names. Specifically,
<DEL>, <ESC>, <LFD>, <SPC>, <RET>, and <TAB> all stand for themselves
when seen in this text, or in an init file (*note Readline Init File::).
If your keyboard lacks a <LFD> key, typing <C-j> will produce the
desired character. The <RET> key may be labeled <Return> or <Enter> on
some keyboards.

File: gdb.info, Node: Readline Interaction, Next: Readline Init File, Prev: Introduction and Notation, Up: Command Line Editing
27.2 Readline Interaction
=========================
Often during an interactive session you type in a long line of text,
only to notice that the first word on the line is misspelled. The
Readline library gives you a set of commands for manipulating the text
as you type it in, allowing you to just fix your typo, and not forcing
you to retype the majority of the line. Using these editing commands,
you move the cursor to the place that needs correction, and delete or
insert the text of the corrections. Then, when you are satisfied with
the line, you simply press <RET>. You do not have to be at the end of
the line to press <RET>; the entire line is accepted regardless of the
location of the cursor within the line.
* Menu:
* Readline Bare Essentials:: The least you need to know about Readline.
* Readline Movement Commands:: Moving about the input line.
* Readline Killing Commands:: How to delete text, and how to get it back!
* Readline Arguments:: Giving numeric arguments to commands.
* Searching:: Searching through previous lines.

File: gdb.info, Node: Readline Bare Essentials, Next: Readline Movement Commands, Up: Readline Interaction
27.2.1 Readline Bare Essentials
-------------------------------
In order to enter characters into the line, simply type them. The typed
character appears where the cursor was, and then the cursor moves one
space to the right. If you mistype a character, you can use your erase
character to back up and delete the mistyped character.
Sometimes you may mistype a character, and not notice the error
until you have typed several other characters. In that case, you can
type `C-b' to move the cursor to the left, and then correct your
mistake. Afterwards, you can move the cursor to the right with `C-f'.
When you add text in the middle of a line, you will notice that
characters to the right of the cursor are `pushed over' to make room
for the text that you have inserted. Likewise, when you delete text
behind the cursor, characters to the right of the cursor are `pulled
back' to fill in the blank space created by the removal of the text. A
list of the bare essentials for editing the text of an input line
follows.
`C-b'
Move back one character.
`C-f'
Move forward one character.
<DEL> or <Backspace>
Delete the character to the left of the cursor.
`C-d'
Delete the character underneath the cursor.
Printing characters
Insert the character into the line at the cursor.
`C-_' or `C-x C-u'
Undo the last editing command. You can undo all the way back to an
empty line.
(Depending on your configuration, the <Backspace> key be set to delete
the character to the left of the cursor and the <DEL> key set to delete
the character underneath the cursor, like `C-d', rather than the
character to the left of the cursor.)

File: gdb.info, Node: Readline Movement Commands, Next: Readline Killing Commands, Prev: Readline Bare Essentials, Up: Readline Interaction
27.2.2 Readline Movement Commands
---------------------------------
The above table describes the most basic keystrokes that you need in
order to do editing of the input line. For your convenience, many
other commands have been added in addition to `C-b', `C-f', `C-d', and
<DEL>. Here are some commands for moving more rapidly about the line.
`C-a'
Move to the start of the line.
`C-e'
Move to the end of the line.
`M-f'
Move forward a word, where a word is composed of letters and
digits.
`M-b'
Move backward a word.
`C-l'
Clear the screen, reprinting the current line at the top.
Notice how `C-f' moves forward a character, while `M-f' moves
forward a word. It is a loose convention that control keystrokes
operate on characters while meta keystrokes operate on words.

File: gdb.info, Node: Readline Killing Commands, Next: Readline Arguments, Prev: Readline Movement Commands, Up: Readline Interaction
27.2.3 Readline Killing Commands
--------------------------------
"Killing" text means to delete the text from the line, but to save it
away for later use, usually by "yanking" (re-inserting) it back into
the line. (`Cut' and `paste' are more recent jargon for `kill' and
`yank'.)
If the description for a command says that it `kills' text, then you
can be sure that you can get the text back in a different (or the same)
place later.
When you use a kill command, the text is saved in a "kill-ring".
Any number of consecutive kills save all of the killed text together, so
that when you yank it back, you get it all. The kill ring is not line
specific; the text that you killed on a previously typed line is
available to be yanked back later, when you are typing another line.
Here is the list of commands for killing text.
`C-k'
Kill the text from the current cursor position to the end of the
line.
`M-d'
Kill from the cursor to the end of the current word, or, if between
words, to the end of the next word. Word boundaries are the same
as those used by `M-f'.
`M-<DEL>'
Kill from the cursor the start of the current word, or, if between
words, to the start of the previous word. Word boundaries are the
same as those used by `M-b'.
`C-w'
Kill from the cursor to the previous whitespace. This is
different than `M-<DEL>' because the word boundaries differ.
Here is how to "yank" the text back into the line. Yanking means to
copy the most-recently-killed text from the kill buffer.
`C-y'
Yank the most recently killed text back into the buffer at the
cursor.
`M-y'
Rotate the kill-ring, and yank the new top. You can only do this
if the prior command is `C-y' or `M-y'.

File: gdb.info, Node: Readline Arguments, Next: Searching, Prev: Readline Killing Commands, Up: Readline Interaction
27.2.4 Readline Arguments
-------------------------
You can pass numeric arguments to Readline commands. Sometimes the
argument acts as a repeat count, other times it is the sign of the
argument that is significant. If you pass a negative argument to a
command which normally acts in a forward direction, that command will
act in a backward direction. For example, to kill text back to the
start of the line, you might type `M-- C-k'.
The general way to pass numeric arguments to a command is to type
meta digits before the command. If the first `digit' typed is a minus
sign (`-'), then the sign of the argument will be negative. Once you
have typed one meta digit to get the argument started, you can type the
remainder of the digits, and then the command. For example, to give
the `C-d' command an argument of 10, you could type `M-1 0 C-d', which
will delete the next ten characters on the input line.

File: gdb.info, Node: Searching, Prev: Readline Arguments, Up: Readline Interaction
27.2.5 Searching for Commands in the History
--------------------------------------------
Readline provides commands for searching through the command history
for lines containing a specified string. There are two search modes:
"incremental" and "non-incremental".
Incremental searches begin before the user has finished typing the
search string. As each character of the search string is typed,
Readline displays the next entry from the history matching the string
typed so far. An incremental search requires only as many characters
as needed to find the desired history entry. To search backward in the
history for a particular string, type `C-r'. Typing `C-s' searches
forward through the history. The characters present in the value of
the `isearch-terminators' variable are used to terminate an incremental
search. If that variable has not been assigned a value, the <ESC> and
`C-J' characters will terminate an incremental search. `C-g' will
abort an incremental search and restore the original line. When the
search is terminated, the history entry containing the search string
becomes the current line.
To find other matching entries in the history list, type `C-r' or
`C-s' as appropriate. This will search backward or forward in the
history for the next entry matching the search string typed so far.
Any other key sequence bound to a Readline command will terminate the
search and execute that command. For instance, a <RET> will terminate
the search and accept the line, thereby executing the command from the
history list. A movement command will terminate the search, make the
last line found the current line, and begin editing.
Readline remembers the last incremental search string. If two
`C-r's are typed without any intervening characters defining a new
search string, any remembered search string is used.
Non-incremental searches read the entire search string before
starting to search for matching history lines. The search string may be
typed by the user or be part of the contents of the current line.

File: gdb.info, Node: Readline Init File, Next: Bindable Readline Commands, Prev: Readline Interaction, Up: Command Line Editing
27.3 Readline Init File
=======================
Although the Readline library comes with a set of Emacs-like
keybindings installed by default, it is possible to use a different set
of keybindings. Any user can customize programs that use Readline by
putting commands in an "inputrc" file, conventionally in his home
directory. The name of this file is taken from the value of the
environment variable `INPUTRC'. If that variable is unset, the default
is `~/.inputrc'.
When a program which uses the Readline library starts up, the init
file is read, and the key bindings are set.
In addition, the `C-x C-r' command re-reads this init file, thus
incorporating any changes that you might have made to it.
* Menu:
* Readline Init File Syntax:: Syntax for the commands in the inputrc file.
* Conditional Init Constructs:: Conditional key bindings in the inputrc file.
* Sample Init File:: An example inputrc file.

File: gdb.info, Node: Readline Init File Syntax, Next: Conditional Init Constructs, Up: Readline Init File
27.3.1 Readline Init File Syntax
--------------------------------
There are only a few basic constructs allowed in the Readline init
file. Blank lines are ignored. Lines beginning with a `#' are
comments. Lines beginning with a `$' indicate conditional constructs
(*note Conditional Init Constructs::). Other lines denote variable
settings and key bindings.
Variable Settings
You can modify the run-time behavior of Readline by altering the
values of variables in Readline using the `set' command within the
init file. The syntax is simple:
set VARIABLE VALUE
Here, for example, is how to change from the default Emacs-like
key binding to use `vi' line editing commands:
set editing-mode vi
Variable names and values, where appropriate, are recognized
without regard to case. Unrecognized variable names are ignored.
Boolean variables (those that can be set to on or off) are set to
on if the value is null or empty, ON (case-insensitive), or 1.
Any other value results in the variable being set to off.
A great deal of run-time behavior is changeable with the following
variables.
`bell-style'
Controls what happens when Readline wants to ring the
terminal bell. If set to `none', Readline never rings the
bell. If set to `visible', Readline uses a visible bell if
one is available. If set to `audible' (the default),
Readline attempts to ring the terminal's bell.
`bind-tty-special-chars'
If set to `on', Readline attempts to bind the control
characters treated specially by the kernel's terminal driver
to their Readline equivalents.
`comment-begin'
The string to insert at the beginning of the line when the
`insert-comment' command is executed. The default value is
`"#"'.
`completion-ignore-case'
If set to `on', Readline performs filename matching and
completion in a case-insensitive fashion. The default value
is `off'.
`completion-query-items'
The number of possible completions that determines when the
user is asked whether the list of possibilities should be
displayed. If the number of possible completions is greater
than this value, Readline will ask the user whether or not he
wishes to view them; otherwise, they are simply listed. This
variable must be set to an integer value greater than or
equal to 0. A negative value means Readline should never ask.
The default limit is `100'.
`convert-meta'
If set to `on', Readline will convert characters with the
eighth bit set to an ASCII key sequence by stripping the
eighth bit and prefixing an <ESC> character, converting them
to a meta-prefixed key sequence. The default value is `on'.
`disable-completion'
If set to `On', Readline will inhibit word completion.
Completion characters will be inserted into the line as if
they had been mapped to `self-insert'. The default is `off'.
`editing-mode'
The `editing-mode' variable controls which default set of key
bindings is used. By default, Readline starts up in Emacs
editing mode, where the keystrokes are most similar to Emacs.
This variable can be set to either `emacs' or `vi'.
`enable-keypad'
When set to `on', Readline will try to enable the application
keypad when it is called. Some systems need this to enable
the arrow keys. The default is `off'.
`expand-tilde'
If set to `on', tilde expansion is performed when Readline
attempts word completion. The default is `off'.
`history-preserve-point'
If set to `on', the history code attempts to place point at
the same location on each history line retrieved with
`previous-history' or `next-history'. The default is `off'.
`horizontal-scroll-mode'
This variable can be set to either `on' or `off'. Setting it
to `on' means that the text of the lines being edited will
scroll horizontally on a single screen line when they are
longer than the width of the screen, instead of wrapping onto
a new screen line. By default, this variable is set to `off'.
`input-meta'
If set to `on', Readline will enable eight-bit input (it will
not clear the eighth bit in the characters it reads),
regardless of what the terminal claims it can support. The
default value is `off'. The name `meta-flag' is a synonym
for this variable.
`isearch-terminators'
The string of characters that should terminate an incremental
search without subsequently executing the character as a
command (*note Searching::). If this variable has not been
given a value, the characters <ESC> and `C-J' will terminate
an incremental search.
`keymap'
Sets Readline's idea of the current keymap for key binding
commands. Acceptable `keymap' names are `emacs',
`emacs-standard', `emacs-meta', `emacs-ctlx', `vi', `vi-move',
`vi-command', and `vi-insert'. `vi' is equivalent to
`vi-command'; `emacs' is equivalent to `emacs-standard'. The
default value is `emacs'. The value of the `editing-mode'
variable also affects the default keymap.
`mark-directories'
If set to `on', completed directory names have a slash
appended. The default is `on'.
`mark-modified-lines'
This variable, when set to `on', causes Readline to display an
asterisk (`*') at the start of history lines which have been
modified. This variable is `off' by default.
`mark-symlinked-directories'
If set to `on', completed names which are symbolic links to
directories have a slash appended (subject to the value of
`mark-directories'). The default is `off'.
`match-hidden-files'
This variable, when set to `on', causes Readline to match
files whose names begin with a `.' (hidden files) when
performing filename completion, unless the leading `.' is
supplied by the user in the filename to be completed. This
variable is `on' by default.
`output-meta'
If set to `on', Readline will display characters with the
eighth bit set directly rather than as a meta-prefixed escape
sequence. The default is `off'.
`page-completions'
If set to `on', Readline uses an internal `more'-like pager
to display a screenful of possible completions at a time.
This variable is `on' by default.
`print-completions-horizontally'
If set to `on', Readline will display completions with matches
sorted horizontally in alphabetical order, rather than down
the screen. The default is `off'.
`show-all-if-ambiguous'
This alters the default behavior of the completion functions.
If set to `on', words which have more than one possible
completion cause the matches to be listed immediately instead
of ringing the bell. The default value is `off'.
`show-all-if-unmodified'
This alters the default behavior of the completion functions
in a fashion similar to SHOW-ALL-IF-AMBIGUOUS. If set to
`on', words which have more than one possible completion
without any possible partial completion (the possible
completions don't share a common prefix) cause the matches to
be listed immediately instead of ringing the bell. The
default value is `off'.
`visible-stats'
If set to `on', a character denoting a file's type is
appended to the filename when listing possible completions.
The default is `off'.
Key Bindings
The syntax for controlling key bindings in the init file is
simple. First you need to find the name of the command that you
want to change. The following sections contain tables of the
command name, the default keybinding, if any, and a short
description of what the command does.
Once you know the name of the command, simply place on a line in
the init file the name of the key you wish to bind the command to,
a colon, and then the name of the command. The name of the key
can be expressed in different ways, depending on what you find most
comfortable.
In addition to command names, readline allows keys to be bound to
a string that is inserted when the key is pressed (a MACRO).
KEYNAME: FUNCTION-NAME or MACRO
KEYNAME is the name of a key spelled out in English. For
example:
Control-u: universal-argument
Meta-Rubout: backward-kill-word
Control-o: "> output"
In the above example, `C-u' is bound to the function
`universal-argument', `M-DEL' is bound to the function
`backward-kill-word', and `C-o' is bound to run the macro
expressed on the right hand side (that is, to insert the text
`> output' into the line).
A number of symbolic character names are recognized while
processing this key binding syntax: DEL, ESC, ESCAPE, LFD,
NEWLINE, RET, RETURN, RUBOUT, SPACE, SPC, and TAB.
"KEYSEQ": FUNCTION-NAME or MACRO
KEYSEQ differs from KEYNAME above in that strings denoting an
entire key sequence can be specified, by placing the key
sequence in double quotes. Some GNU Emacs style key escapes
can be used, as in the following example, but the special
character names are not recognized.
"\C-u": universal-argument
"\C-x\C-r": re-read-init-file
"\e[11~": "Function Key 1"
In the above example, `C-u' is again bound to the function
`universal-argument' (just as it was in the first example),
`C-x C-r' is bound to the function `re-read-init-file', and
`<ESC> <[> <1> <1> <~>' is bound to insert the text `Function
Key 1'.
The following GNU Emacs style escape sequences are available when
specifying key sequences:
`\C-'
control prefix
`\M-'
meta prefix
`\e'
an escape character
`\\'
backslash
`\"'
<">, a double quotation mark
`\''
<'>, a single quote or apostrophe
In addition to the GNU Emacs style escape sequences, a second set
of backslash escapes is available:
`\a'
alert (bell)
`\b'
backspace
`\d'
delete
`\f'
form feed
`\n'
newline
`\r'
carriage return
`\t'
horizontal tab
`\v'
vertical tab
`\NNN'
the eight-bit character whose value is the octal value NNN
(one to three digits)
`\xHH'
the eight-bit character whose value is the hexadecimal value
HH (one or two hex digits)
When entering the text of a macro, single or double quotes must be
used to indicate a macro definition. Unquoted text is assumed to
be a function name. In the macro body, the backslash escapes
described above are expanded. Backslash will quote any other
character in the macro text, including `"' and `''. For example,
the following binding will make `C-x \' insert a single `\' into
the line:
"\C-x\\": "\\"

File: gdb.info, Node: Conditional Init Constructs, Next: Sample Init File, Prev: Readline Init File Syntax, Up: Readline Init File
27.3.2 Conditional Init Constructs
----------------------------------
Readline implements a facility similar in spirit to the conditional
compilation features of the C preprocessor which allows key bindings
and variable settings to be performed as the result of tests. There
are four parser directives used.
`$if'
The `$if' construct allows bindings to be made based on the
editing mode, the terminal being used, or the application using
Readline. The text of the test extends to the end of the line; no
characters are required to isolate it.
`mode'
The `mode=' form of the `$if' directive is used to test
whether Readline is in `emacs' or `vi' mode. This may be
used in conjunction with the `set keymap' command, for
instance, to set bindings in the `emacs-standard' and
`emacs-ctlx' keymaps only if Readline is starting out in
`emacs' mode.
`term'
The `term=' form may be used to include terminal-specific key
bindings, perhaps to bind the key sequences output by the
terminal's function keys. The word on the right side of the
`=' is tested against both the full name of the terminal and
the portion of the terminal name before the first `-'. This
allows `sun' to match both `sun' and `sun-cmd', for instance.
`application'
The APPLICATION construct is used to include
application-specific settings. Each program using the
Readline library sets the APPLICATION NAME, and you can test
for a particular value. This could be used to bind key
sequences to functions useful for a specific program. For
instance, the following command adds a key sequence that
quotes the current or previous word in Bash:
$if Bash
# Quote the current or previous word
"\C-xq": "\eb\"\ef\""
$endif
`$endif'
This command, as seen in the previous example, terminates an `$if'
command.
`$else'
Commands in this branch of the `$if' directive are executed if the
test fails.
`$include'
This directive takes a single filename as an argument and reads
commands and bindings from that file. For example, the following
directive reads from `/etc/inputrc':
$include /etc/inputrc

File: gdb.info, Node: Sample Init File, Prev: Conditional Init Constructs, Up: Readline Init File
27.3.3 Sample Init File
-----------------------
Here is an example of an INPUTRC file. This illustrates key binding,
variable assignment, and conditional syntax.
# This file controls the behaviour of line input editing for
# programs that use the GNU Readline library. Existing
# programs include FTP, Bash, and GDB.
#
# You can re-read the inputrc file with C-x C-r.
# Lines beginning with '#' are comments.
#
# First, include any systemwide bindings and variable
# assignments from /etc/Inputrc
$include /etc/Inputrc
#
# Set various bindings for emacs mode.
set editing-mode emacs
$if mode=emacs
Meta-Control-h: backward-kill-word Text after the function name is ignored
#
# Arrow keys in keypad mode
#
#"\M-OD": backward-char
#"\M-OC": forward-char
#"\M-OA": previous-history
#"\M-OB": next-history
#
# Arrow keys in ANSI mode
#
"\M-[D": backward-char
"\M-[C": forward-char
"\M-[A": previous-history
"\M-[B": next-history
#
# Arrow keys in 8 bit keypad mode
#
#"\M-\C-OD": backward-char
#"\M-\C-OC": forward-char
#"\M-\C-OA": previous-history
#"\M-\C-OB": next-history
#
# Arrow keys in 8 bit ANSI mode
#
#"\M-\C-[D": backward-char
#"\M-\C-[C": forward-char
#"\M-\C-[A": previous-history
#"\M-\C-[B": next-history
C-q: quoted-insert
$endif
# An old-style binding. This happens to be the default.
TAB: complete
# Macros that are convenient for shell interaction
$if Bash
# edit the path
"\C-xp": "PATH=${PATH}\e\C-e\C-a\ef\C-f"
# prepare to type a quoted word --
# insert open and close double quotes
# and move to just after the open quote
"\C-x\"": "\"\"\C-b"
# insert a backslash (testing backslash escapes
# in sequences and macros)
"\C-x\\": "\\"
# Quote the current or previous word
"\C-xq": "\eb\"\ef\""
# Add a binding to refresh the line, which is unbound
"\C-xr": redraw-current-line
# Edit variable on current line.
"\M-\C-v": "\C-a\C-k$\C-y\M-\C-e\C-a\C-y="
$endif
# use a visible bell if one is available
set bell-style visible
# don't strip characters to 7 bits when reading
set input-meta on
# allow iso-latin1 characters to be inserted rather
# than converted to prefix-meta sequences
set convert-meta off
# display characters with the eighth bit set directly
# rather than as meta-prefixed characters
set output-meta on
# if there are more than 150 possible completions for
# a word, ask the user if he wants to see all of them
set completion-query-items 150
# For FTP
$if Ftp
"\C-xg": "get \M-?"
"\C-xt": "put \M-?"
"\M-.": yank-last-arg
$endif

File: gdb.info, Node: Bindable Readline Commands, Next: Readline vi Mode, Prev: Readline Init File, Up: Command Line Editing
27.4 Bindable Readline Commands
===============================
* Menu:
* Commands For Moving:: Moving about the line.
* Commands For History:: Getting at previous lines.
* Commands For Text:: Commands for changing text.
* Commands For Killing:: Commands for killing and yanking.
* Numeric Arguments:: Specifying numeric arguments, repeat counts.
* Commands For Completion:: Getting Readline to do the typing for you.
* Keyboard Macros:: Saving and re-executing typed characters
* Miscellaneous Commands:: Other miscellaneous commands.
This section describes Readline commands that may be bound to key
sequences. Command names without an accompanying key sequence are
unbound by default.
In the following descriptions, "point" refers to the current cursor
position, and "mark" refers to a cursor position saved by the
`set-mark' command. The text between the point and mark is referred to
as the "region".

File: gdb.info, Node: Commands For Moving, Next: Commands For History, Up: Bindable Readline Commands
27.4.1 Commands For Moving
--------------------------
`beginning-of-line (C-a)'
Move to the start of the current line.
`end-of-line (C-e)'
Move to the end of the line.
`forward-char (C-f)'
Move forward a character.
`backward-char (C-b)'
Move back a character.
`forward-word (M-f)'
Move forward to the end of the next word. Words are composed of
letters and digits.
`backward-word (M-b)'
Move back to the start of the current or previous word. Words are
composed of letters and digits.
`clear-screen (C-l)'
Clear the screen and redraw the current line, leaving the current
line at the top of the screen.
`redraw-current-line ()'
Refresh the current line. By default, this is unbound.

File: gdb.info, Node: Commands For History, Next: Commands For Text, Prev: Commands For Moving, Up: Bindable Readline Commands
27.4.2 Commands For Manipulating The History
--------------------------------------------
`accept-line (Newline or Return)'
Accept the line regardless of where the cursor is. If this line is
non-empty, it may be added to the history list for future recall
with `add_history()'. If this line is a modified history line,
the history line is restored to its original state.
`previous-history (C-p)'
Move `back' through the history list, fetching the previous
command.
`next-history (C-n)'
Move `forward' through the history list, fetching the next command.
`beginning-of-history (M-<)'
Move to the first line in the history.
`end-of-history (M->)'
Move to the end of the input history, i.e., the line currently
being entered.
`reverse-search-history (C-r)'
Search backward starting at the current line and moving `up'
through the history as necessary. This is an incremental search.
`forward-search-history (C-s)'
Search forward starting at the current line and moving `down'
through the the history as necessary. This is an incremental
search.
`non-incremental-reverse-search-history (M-p)'
Search backward starting at the current line and moving `up'
through the history as necessary using a non-incremental search
for a string supplied by the user.
`non-incremental-forward-search-history (M-n)'
Search forward starting at the current line and moving `down'
through the the history as necessary using a non-incremental search
for a string supplied by the user.
`history-search-forward ()'
Search forward through the history for the string of characters
between the start of the current line and the point. This is a
non-incremental search. By default, this command is unbound.
`history-search-backward ()'
Search backward through the history for the string of characters
between the start of the current line and the point. This is a
non-incremental search. By default, this command is unbound.
`yank-nth-arg (M-C-y)'
Insert the first argument to the previous command (usually the
second word on the previous line) at point. With an argument N,
insert the Nth word from the previous command (the words in the
previous command begin with word 0). A negative argument inserts
the Nth word from the end of the previous command. Once the
argument N is computed, the argument is extracted as if the `!N'
history expansion had been specified.
`yank-last-arg (M-. or M-_)'
Insert last argument to the previous command (the last word of the
previous history entry). With an argument, behave exactly like
`yank-nth-arg'. Successive calls to `yank-last-arg' move back
through the history list, inserting the last argument of each line
in turn. The history expansion facilities are used to extract the
last argument, as if the `!$' history expansion had been specified.

File: gdb.info, Node: Commands For Text, Next: Commands For Killing, Prev: Commands For History, Up: Bindable Readline Commands
27.4.3 Commands For Changing Text
---------------------------------
`delete-char (C-d)'
Delete the character at point. If point is at the beginning of
the line, there are no characters in the line, and the last
character typed was not bound to `delete-char', then return EOF.
`backward-delete-char (Rubout)'
Delete the character behind the cursor. A numeric argument means
to kill the characters instead of deleting them.
`forward-backward-delete-char ()'
Delete the character under the cursor, unless the cursor is at the
end of the line, in which case the character behind the cursor is
deleted. By default, this is not bound to a key.
`quoted-insert (C-q or C-v)'
Add the next character typed to the line verbatim. This is how to
insert key sequences like `C-q', for example.
`tab-insert (M-<TAB>)'
Insert a tab character.
`self-insert (a, b, A, 1, !, ...)'
Insert yourself.
`transpose-chars (C-t)'
Drag the character before the cursor forward over the character at
the cursor, moving the cursor forward as well. If the insertion
point is at the end of the line, then this transposes the last two
characters of the line. Negative arguments have no effect.
`transpose-words (M-t)'
Drag the word before point past the word after point, moving point
past that word as well. If the insertion point is at the end of
the line, this transposes the last two words on the line.
`upcase-word (M-u)'
Uppercase the current (or following) word. With a negative
argument, uppercase the previous word, but do not move the cursor.
`downcase-word (M-l)'
Lowercase the current (or following) word. With a negative
argument, lowercase the previous word, but do not move the cursor.
`capitalize-word (M-c)'
Capitalize the current (or following) word. With a negative
argument, capitalize the previous word, but do not move the cursor.
`overwrite-mode ()'
Toggle overwrite mode. With an explicit positive numeric argument,
switches to overwrite mode. With an explicit non-positive numeric
argument, switches to insert mode. This command affects only
`emacs' mode; `vi' mode does overwrite differently. Each call to
`readline()' starts in insert mode.
In overwrite mode, characters bound to `self-insert' replace the
text at point rather than pushing the text to the right.
Characters bound to `backward-delete-char' replace the character
before point with a space.
By default, this command is unbound.

File: gdb.info, Node: Commands For Killing, Next: Numeric Arguments, Prev: Commands For Text, Up: Bindable Readline Commands
27.4.4 Killing And Yanking
--------------------------
`kill-line (C-k)'
Kill the text from point to the end of the line.
`backward-kill-line (C-x Rubout)'
Kill backward to the beginning of the line.
`unix-line-discard (C-u)'
Kill backward from the cursor to the beginning of the current line.
`kill-whole-line ()'
Kill all characters on the current line, no matter where point is.
By default, this is unbound.
`kill-word (M-d)'
Kill from point to the end of the current word, or if between
words, to the end of the next word. Word boundaries are the same
as `forward-word'.
`backward-kill-word (M-<DEL>)'
Kill the word behind point. Word boundaries are the same as
`backward-word'.
`unix-word-rubout (C-w)'
Kill the word behind point, using white space as a word boundary.
The killed text is saved on the kill-ring.
`unix-filename-rubout ()'
Kill the word behind point, using white space and the slash
character as the word boundaries. The killed text is saved on the
kill-ring.
`delete-horizontal-space ()'
Delete all spaces and tabs around point. By default, this is
unbound.
`kill-region ()'
Kill the text in the current region. By default, this command is
unbound.
`copy-region-as-kill ()'
Copy the text in the region to the kill buffer, so it can be yanked
right away. By default, this command is unbound.
`copy-backward-word ()'
Copy the word before point to the kill buffer. The word
boundaries are the same as `backward-word'. By default, this
command is unbound.
`copy-forward-word ()'
Copy the word following point to the kill buffer. The word
boundaries are the same as `forward-word'. By default, this
command is unbound.
`yank (C-y)'
Yank the top of the kill ring into the buffer at point.
`yank-pop (M-y)'
Rotate the kill-ring, and yank the new top. You can only do this
if the prior command is `yank' or `yank-pop'.

File: gdb.info, Node: Numeric Arguments, Next: Commands For Completion, Prev: Commands For Killing, Up: Bindable Readline Commands
27.4.5 Specifying Numeric Arguments
-----------------------------------
`digit-argument (M-0, M-1, ... M--)'
Add this digit to the argument already accumulating, or start a new
argument. `M--' starts a negative argument.
`universal-argument ()'
This is another way to specify an argument. If this command is
followed by one or more digits, optionally with a leading minus
sign, those digits define the argument. If the command is
followed by digits, executing `universal-argument' again ends the
numeric argument, but is otherwise ignored. As a special case, if
this command is immediately followed by a character that is
neither a digit or minus sign, the argument count for the next
command is multiplied by four. The argument count is initially
one, so executing this function the first time makes the argument
count four, a second time makes the argument count sixteen, and so
on. By default, this is not bound to a key.

File: gdb.info, Node: Commands For Completion, Next: Keyboard Macros, Prev: Numeric Arguments, Up: Bindable Readline Commands
27.4.6 Letting Readline Type For You
------------------------------------
`complete (<TAB>)'
Attempt to perform completion on the text before point. The
actual completion performed is application-specific. The default
is filename completion.
`possible-completions (M-?)'
List the possible completions of the text before point.
`insert-completions (M-*)'
Insert all completions of the text before point that would have
been generated by `possible-completions'.
`menu-complete ()'
Similar to `complete', but replaces the word to be completed with
a single match from the list of possible completions. Repeated
execution of `menu-complete' steps through the list of possible
completions, inserting each match in turn. At the end of the list
of completions, the bell is rung (subject to the setting of
`bell-style') and the original text is restored. An argument of N
moves N positions forward in the list of matches; a negative
argument may be used to move backward through the list. This
command is intended to be bound to <TAB>, but is unbound by
default.
`delete-char-or-list ()'
Deletes the character under the cursor if not at the beginning or
end of the line (like `delete-char'). If at the end of the line,
behaves identically to `possible-completions'. This command is
unbound by default.

File: gdb.info, Node: Keyboard Macros, Next: Miscellaneous Commands, Prev: Commands For Completion, Up: Bindable Readline Commands
27.4.7 Keyboard Macros
----------------------
`start-kbd-macro (C-x ()'
Begin saving the characters typed into the current keyboard macro.
`end-kbd-macro (C-x ))'
Stop saving the characters typed into the current keyboard macro
and save the definition.
`call-last-kbd-macro (C-x e)'
Re-execute the last keyboard macro defined, by making the
characters in the macro appear as if typed at the keyboard.

File: gdb.info, Node: Miscellaneous Commands, Prev: Keyboard Macros, Up: Bindable Readline Commands
27.4.8 Some Miscellaneous Commands
----------------------------------
`re-read-init-file (C-x C-r)'
Read in the contents of the INPUTRC file, and incorporate any
bindings or variable assignments found there.
`abort (C-g)'
Abort the current editing command and ring the terminal's bell
(subject to the setting of `bell-style').
`do-uppercase-version (M-a, M-b, M-X, ...)'
If the metafied character X is lowercase, run the command that is
bound to the corresponding uppercase character.
`prefix-meta (<ESC>)'
Metafy the next character typed. This is for keyboards without a
meta key. Typing `<ESC> f' is equivalent to typing `M-f'.
`undo (C-_ or C-x C-u)'
Incremental undo, separately remembered for each line.
`revert-line (M-r)'
Undo all changes made to this line. This is like executing the
`undo' command enough times to get back to the beginning.
`tilde-expand (M-~)'
Perform tilde expansion on the current word.
`set-mark (C-@)'
Set the mark to the point. If a numeric argument is supplied, the
mark is set to that position.
`exchange-point-and-mark (C-x C-x)'
Swap the point with the mark. The current cursor position is set
to the saved position, and the old cursor position is saved as the
mark.
`character-search (C-])'
A character is read and point is moved to the next occurrence of
that character. A negative count searches for previous
occurrences.
`character-search-backward (M-C-])'
A character is read and point is moved to the previous occurrence
of that character. A negative count searches for subsequent
occurrences.
`insert-comment (M-#)'
Without a numeric argument, the value of the `comment-begin'
variable is inserted at the beginning of the current line. If a
numeric argument is supplied, this command acts as a toggle: if
the characters at the beginning of the line do not match the value
of `comment-begin', the value is inserted, otherwise the
characters in `comment-begin' are deleted from the beginning of
the line. In either case, the line is accepted as if a newline
had been typed.
`dump-functions ()'
Print all of the functions and their key bindings to the Readline
output stream. If a numeric argument is supplied, the output is
formatted in such a way that it can be made part of an INPUTRC
file. This command is unbound by default.
`dump-variables ()'
Print all of the settable variables and their values to the
Readline output stream. If a numeric argument is supplied, the
output is formatted in such a way that it can be made part of an
INPUTRC file. This command is unbound by default.
`dump-macros ()'
Print all of the Readline key sequences bound to macros and the
strings they output. If a numeric argument is supplied, the
output is formatted in such a way that it can be made part of an
INPUTRC file. This command is unbound by default.
`emacs-editing-mode (C-e)'
When in `vi' command mode, this causes a switch to `emacs' editing
mode.
`vi-editing-mode (M-C-j)'
When in `emacs' editing mode, this causes a switch to `vi' editing
mode.

File: gdb.info, Node: Readline vi Mode, Prev: Bindable Readline Commands, Up: Command Line Editing
27.5 Readline vi Mode
=====================
While the Readline library does not have a full set of `vi' editing
functions, it does contain enough to allow simple editing of the line.
The Readline `vi' mode behaves as specified in the POSIX 1003.2
standard.
In order to switch interactively between `emacs' and `vi' editing
modes, use the command `M-C-j' (bound to emacs-editing-mode when in
`vi' mode and to vi-editing-mode in `emacs' mode). The Readline
default is `emacs' mode.
When you enter a line in `vi' mode, you are already placed in
`insertion' mode, as if you had typed an `i'. Pressing <ESC> switches
you into `command' mode, where you can edit the text of the line with
the standard `vi' movement keys, move to previous history lines with
`k' and subsequent lines with `j', and so forth.

File: gdb.info, Node: Using History Interactively, Next: Installing GDB, Prev: Command Line Editing, Up: Top
28 Using History Interactively
******************************
This chapter describes how to use the GNU History Library interactively,
from a user's standpoint. It should be considered a user's guide. For
information on using the GNU History Library in other programs, see the
GNU Readline Library Manual.
* Menu:
* History Interaction:: What it feels like using History as a user.

File: gdb.info, Node: History Interaction, Up: Using History Interactively
28.1 History Expansion
======================
The History library provides a history expansion feature that is similar
to the history expansion provided by `csh'. This section describes the
syntax used to manipulate the history information.
History expansions introduce words from the history list into the
input stream, making it easy to repeat commands, insert the arguments
to a previous command into the current input line, or fix errors in
previous commands quickly.
History expansion takes place in two parts. The first is to
determine which line from the history list should be used during
substitution. The second is to select portions of that line for
inclusion into the current one. The line selected from the history is
called the "event", and the portions of that line that are acted upon
are called "words". Various "modifiers" are available to manipulate
the selected words. The line is broken into words in the same fashion
that Bash does, so that several words surrounded by quotes are
considered one word. History expansions are introduced by the
appearance of the history expansion character, which is `!' by default.
* Menu:
* Event Designators:: How to specify which history line to use.
* Word Designators:: Specifying which words are of interest.
* Modifiers:: Modifying the results of substitution.

File: gdb.info, Node: Event Designators, Next: Word Designators, Up: History Interaction
28.1.1 Event Designators
------------------------
An event designator is a reference to a command line entry in the
history list.
`!'
Start a history substitution, except when followed by a space, tab,
the end of the line, or `='.
`!N'
Refer to command line N.
`!-N'
Refer to the command N lines back.
`!!'
Refer to the previous command. This is a synonym for `!-1'.
`!STRING'
Refer to the most recent command starting with STRING.
`!?STRING[?]'
Refer to the most recent command containing STRING. The trailing
`?' may be omitted if the STRING is followed immediately by a
newline.
`^STRING1^STRING2^'
Quick Substitution. Repeat the last command, replacing STRING1
with STRING2. Equivalent to `!!:s/STRING1/STRING2/'.
`!#'
The entire command line typed so far.

File: gdb.info, Node: Word Designators, Next: Modifiers, Prev: Event Designators, Up: History Interaction
28.1.2 Word Designators
-----------------------
Word designators are used to select desired words from the event. A
`:' separates the event specification from the word designator. It may
be omitted if the word designator begins with a `^', `$', `*', `-', or
`%'. Words are numbered from the beginning of the line, with the first
word being denoted by 0 (zero). Words are inserted into the current
line separated by single spaces.
For example,
`!!'
designates the preceding command. When you type this, the
preceding command is repeated in toto.
`!!:$'
designates the last argument of the preceding command. This may be
shortened to `!$'.
`!fi:2'
designates the second argument of the most recent command starting
with the letters `fi'.
Here are the word designators:
`0 (zero)'
The `0'th word. For many applications, this is the command word.
`N'
The Nth word.
`^'
The first argument; that is, word 1.
`$'
The last argument.
`%'
The word matched by the most recent `?STRING?' search.
`X-Y'
A range of words; `-Y' abbreviates `0-Y'.
`*'
All of the words, except the `0'th. This is a synonym for `1-$'.
It is not an error to use `*' if there is just one word in the
event; the empty string is returned in that case.
`X*'
Abbreviates `X-$'
`X-'
Abbreviates `X-$' like `X*', but omits the last word.
If a word designator is supplied without an event specification, the
previous command is used as the event.

File: gdb.info, Node: Modifiers, Prev: Word Designators, Up: History Interaction
28.1.3 Modifiers
----------------
After the optional word designator, you can add a sequence of one or
more of the following modifiers, each preceded by a `:'.
`h'
Remove a trailing pathname component, leaving only the head.
`t'
Remove all leading pathname components, leaving the tail.
`r'
Remove a trailing suffix of the form `.SUFFIX', leaving the
basename.
`e'
Remove all but the trailing suffix.
`p'
Print the new command but do not execute it.
`s/OLD/NEW/'
Substitute NEW for the first occurrence of OLD in the event line.
Any delimiter may be used in place of `/'. The delimiter may be
quoted in OLD and NEW with a single backslash. If `&' appears in
NEW, it is replaced by OLD. A single backslash will quote the
`&'. The final delimiter is optional if it is the last character
on the input line.
`&'
Repeat the previous substitution.
`g'
`a'
Cause changes to be applied over the entire event line. Used in
conjunction with `s', as in `gs/OLD/NEW/', or with `&'.
`G'
Apply the following `s' modifier once to each word in the event.

File: gdb.info, Node: Formatting Documentation, Next: Command Line Editing, Prev: GDB Bugs, Up: Top
Appendix A Formatting Documentation
***********************************
The GDB 4 release includes an already-formatted reference card, ready
for printing with PostScript or Ghostscript, in the `gdb' subdirectory
of the main source directory(1). If you can use PostScript or
Ghostscript with your printer, you can print the reference card
immediately with `refcard.ps'.
The release also includes the source for the reference card. You
can format it, using TeX, by typing:
make refcard.dvi
The GDB reference card is designed to print in "landscape" mode on
US "letter" size paper; that is, on a sheet 11 inches wide by 8.5 inches
high. You will need to specify this form of printing as an option to
your DVI output program.
All the documentation for GDB comes as part of the machine-readable
distribution. The documentation is written in Texinfo format, which is
a documentation system that uses a single source file to produce both
on-line information and a printed manual. You can use one of the Info
formatting commands to create the on-line version of the documentation
and TeX (or `texi2roff') to typeset the printed version.
GDB includes an already formatted copy of the on-line Info version
of this manual in the `gdb' subdirectory. The main Info file is
`gdb-6.6/gdb/gdb.info', and it refers to subordinate files matching
`gdb.info*' in the same directory. If necessary, you can print out
these files, or read them with any editor; but they are easier to read
using the `info' subsystem in GNU Emacs or the standalone `info'
program, available as part of the GNU Texinfo distribution.
If you want to format these Info files yourself, you need one of the
Info formatting programs, such as `texinfo-format-buffer' or `makeinfo'.
If you have `makeinfo' installed, and are in the top level GDB
source directory (`gdb-6.6', in the case of version 6.6), you can make
the Info file by typing:
cd gdb
make gdb.info
If you want to typeset and print copies of this manual, you need TeX,
a program to print its DVI output files, and `texinfo.tex', the Texinfo
definitions file.
TeX is a typesetting program; it does not print files directly, but
produces output files called DVI files. To print a typeset document,
you need a program to print DVI files. If your system has TeX
installed, chances are it has such a program. The precise command to
use depends on your system; `lpr -d' is common; another (for PostScript
devices) is `dvips'. The DVI print command may require a file name
without any extension or a `.dvi' extension.
TeX also requires a macro definitions file called `texinfo.tex'.
This file tells TeX how to typeset a document written in Texinfo
format. On its own, TeX cannot either read or typeset a Texinfo file.
`texinfo.tex' is distributed with GDB and is located in the
`gdb-VERSION-NUMBER/texinfo' directory.
If you have TeX and a DVI printer program installed, you can typeset
and print this manual. First switch to the the `gdb' subdirectory of
the main source directory (for example, to `gdb-6.6/gdb') and type:
make gdb.dvi
Then give `gdb.dvi' to your DVI printing program.
---------- Footnotes ----------
(1) In `gdb-6.6/gdb/refcard.ps' of the version 6.6 release.

File: gdb.info, Node: Installing GDB, Next: Maintenance Commands, Prev: Using History Interactively, Up: Top
Appendix B Installing GDB
*************************
* Menu:
* Requirements:: Requirements for building GDB
* Running Configure:: Invoking the GDB `configure' script
* Separate Objdir:: Compiling GDB in another directory
* Config Names:: Specifying names for hosts and targets
* Configure Options:: Summary of options for configure

File: gdb.info, Node: Requirements, Next: Running Configure, Up: Installing GDB
B.1 Requirements for building GDB
=================================
Building GDB requires various tools and packages to be available.
Other packages will be used only if they are found.
Tools/packages necessary for building GDB
=========================================
ISO C90 compiler
GDB is written in ISO C90. It should be buildable with any
working C90 compiler, e.g. GCC.
Tools/packages optional for building GDB
========================================
Expat
GDB can use the Expat XML parsing library. This library may be
included with your operating system distribution; if it is not, you
can get the latest version from `http://expat.sourceforge.net'.
The `configure' script will search for this library in several
standard locations; if it is installed in an unusual path, you can
use the `--with-libexpat-prefix' option to specify its location.
Expat is used currently only used to implement some remote-specific
features.

File: gdb.info, Node: Running Configure, Next: Separate Objdir, Prev: Requirements, Up: Installing GDB
B.2 Invoking the GDB `configure' script
=======================================
GDB comes with a `configure' script that automates the process of
preparing GDB for installation; you can then use `make' to build the
`gdb' program.
The GDB distribution includes all the source code you need for GDB
in a single directory, whose name is usually composed by appending the
version number to `gdb'.
For example, the GDB version 6.6 distribution is in the `gdb-6.6'
directory. That directory contains:
`gdb-6.6/configure (and supporting files)'
script for configuring GDB and all its supporting libraries
`gdb-6.6/gdb'
the source specific to GDB itself
`gdb-6.6/bfd'
source for the Binary File Descriptor library
`gdb-6.6/include'
GNU include files
`gdb-6.6/libiberty'
source for the `-liberty' free software library
`gdb-6.6/opcodes'
source for the library of opcode tables and disassemblers
`gdb-6.6/readline'
source for the GNU command-line interface
`gdb-6.6/glob'
source for the GNU filename pattern-matching subroutine
`gdb-6.6/mmalloc'
source for the GNU memory-mapped malloc package
The simplest way to configure and build GDB is to run `configure'
from the `gdb-VERSION-NUMBER' source directory, which in this example
is the `gdb-6.6' directory.
First switch to the `gdb-VERSION-NUMBER' source directory if you are
not already in it; then run `configure'. Pass the identifier for the
platform on which GDB will run as an argument.
For example:
cd gdb-6.6
./configure HOST
make
where HOST is an identifier such as `sun4' or `decstation', that
identifies the platform where GDB will run. (You can often leave off
HOST; `configure' tries to guess the correct value by examining your
system.)
Running `configure HOST' and then running `make' builds the `bfd',
`readline', `mmalloc', and `libiberty' libraries, then `gdb' itself.
The configured source files, and the binaries, are left in the
corresponding source directories.
`configure' is a Bourne-shell (`/bin/sh') script; if your system
does not recognize this automatically when you run a different shell,
you may need to run `sh' on it explicitly:
sh configure HOST
If you run `configure' from a directory that contains source
directories for multiple libraries or programs, such as the `gdb-6.6'
source directory for version 6.6, `configure' creates configuration
files for every directory level underneath (unless you tell it not to,
with the `--norecursion' option).
You should run the `configure' script from the top directory in the
source tree, the `gdb-VERSION-NUMBER' directory. If you run
`configure' from one of the subdirectories, you will configure only
that subdirectory. That is usually not what you want. In particular,
if you run the first `configure' from the `gdb' subdirectory of the
`gdb-VERSION-NUMBER' directory, you will omit the configuration of
`bfd', `readline', and other sibling directories of the `gdb'
subdirectory. This leads to build errors about missing include files
such as `bfd/bfd.h'.
You can install `gdb' anywhere; it has no hardwired paths. However,
you should make sure that the shell on your path (named by the `SHELL'
environment variable) is publicly readable. Remember that GDB uses the
shell to start your program--some systems refuse to let GDB debug child
processes whose programs are not readable.

File: gdb.info, Node: Separate Objdir, Next: Config Names, Prev: Running Configure, Up: Installing GDB
B.3 Compiling GDB in another directory
======================================
If you want to run GDB versions for several host or target machines,
you need a different `gdb' compiled for each combination of host and
target. `configure' is designed to make this easy by allowing you to
generate each configuration in a separate subdirectory, rather than in
the source directory. If your `make' program handles the `VPATH'
feature (GNU `make' does), running `make' in each of these directories
builds the `gdb' program specified there.
To build `gdb' in a separate directory, run `configure' with the
`--srcdir' option to specify where to find the source. (You also need
to specify a path to find `configure' itself from your working
directory. If the path to `configure' would be the same as the
argument to `--srcdir', you can leave out the `--srcdir' option; it is
assumed.)
For example, with version 6.6, you can build GDB in a separate
directory for a Sun 4 like this:
cd gdb-6.6
mkdir ../gdb-sun4
cd ../gdb-sun4
../gdb-6.6/configure sun4
make
When `configure' builds a configuration using a remote source
directory, it creates a tree for the binaries with the same structure
(and using the same names) as the tree under the source directory. In
the example, you'd find the Sun 4 library `libiberty.a' in the
directory `gdb-sun4/libiberty', and GDB itself in `gdb-sun4/gdb'.
Make sure that your path to the `configure' script has just one
instance of `gdb' in it. If your path to `configure' looks like
`../gdb-6.6/gdb/configure', you are configuring only one subdirectory
of GDB, not the whole package. This leads to build errors about
missing include files such as `bfd/bfd.h'.
One popular reason to build several GDB configurations in separate
directories is to configure GDB for cross-compiling (where GDB runs on
one machine--the "host"--while debugging programs that run on another
machine--the "target"). You specify a cross-debugging target by giving
the `--target=TARGET' option to `configure'.
When you run `make' to build a program or library, you must run it
in a configured directory--whatever directory you were in when you
called `configure' (or one of its subdirectories).
The `Makefile' that `configure' generates in each source directory
also runs recursively. If you type `make' in a source directory such
as `gdb-6.6' (or in a separate configured directory configured with
`--srcdir=DIRNAME/gdb-6.6'), you will build all the required libraries,
and then build GDB.
When you have multiple hosts or targets configured in separate
directories, you can run `make' on them in parallel (for example, if
they are NFS-mounted on each of the hosts); they will not interfere
with each other.

File: gdb.info, Node: Config Names, Next: Configure Options, Prev: Separate Objdir, Up: Installing GDB
B.4 Specifying names for hosts and targets
==========================================
The specifications used for hosts and targets in the `configure' script
are based on a three-part naming scheme, but some short predefined
aliases are also supported. The full naming scheme encodes three pieces
of information in the following pattern:
ARCHITECTURE-VENDOR-OS
For example, you can use the alias `sun4' as a HOST argument, or as
the value for TARGET in a `--target=TARGET' option. The equivalent
full name is `sparc-sun-sunos4'.
The `configure' script accompanying GDB does not provide any query
facility to list all supported host and target names or aliases.
`configure' calls the Bourne shell script `config.sub' to map
abbreviations to full names; you can read the script, if you wish, or
you can use it to test your guesses on abbreviations--for example:
% sh config.sub i386-linux
i386-pc-linux-gnu
% sh config.sub alpha-linux
alpha-unknown-linux-gnu
% sh config.sub hp9k700
hppa1.1-hp-hpux
% sh config.sub sun4
sparc-sun-sunos4.1.1
% sh config.sub sun3
m68k-sun-sunos4.1.1
% sh config.sub i986v
Invalid configuration `i986v': machine `i986v' not recognized
`config.sub' is also distributed in the GDB source directory
(`gdb-6.6', for version 6.6).

File: gdb.info, Node: Configure Options, Prev: Config Names, Up: Installing GDB
B.5 `configure' options
=======================
Here is a summary of the `configure' options and arguments that are
most often useful for building GDB. `configure' also has several other
options not listed here. *note (configure.info)What Configure Does::,
for a full explanation of `configure'.
configure [--help]
[--prefix=DIR]
[--exec-prefix=DIR]
[--srcdir=DIRNAME]
[--norecursion] [--rm]
[--target=TARGET]
HOST
You may introduce options with a single `-' rather than `--' if you
prefer; but you may abbreviate option names if you use `--'.
`--help'
Display a quick summary of how to invoke `configure'.
`--prefix=DIR'
Configure the source to install programs and files under directory
`DIR'.
`--exec-prefix=DIR'
Configure the source to install programs under directory `DIR'.
`--srcdir=DIRNAME'
*Warning: using this option requires GNU `make', or another `make'
that implements the `VPATH' feature.*
Use this option to make configurations in directories separate
from the GDB source directories. Among other things, you can use
this to build (or maintain) several configurations simultaneously,
in separate directories. `configure' writes configuration
specific files in the current directory, but arranges for them to
use the source in the directory DIRNAME. `configure' creates
directories under the working directory in parallel to the source
directories below DIRNAME.
`--norecursion'
Configure only the directory level where `configure' is executed;
do not propagate configuration to subdirectories.
`--target=TARGET'
Configure GDB for cross-debugging programs running on the specified
TARGET. Without this option, GDB is configured to debug programs
that run on the same machine (HOST) as GDB itself.
There is no convenient way to generate a list of all available
targets.
`HOST ...'
Configure GDB to run on the specified HOST.
There is no convenient way to generate a list of all available
hosts.
There are many other options available as well, but they are
generally needed for special purposes only.

File: gdb.info, Node: Maintenance Commands, Next: Remote Protocol, Prev: Installing GDB, Up: Top
Appendix C Maintenance Commands
*******************************
In addition to commands intended for GDB users, GDB includes a number
of commands intended for GDB developers, that are not documented
elsewhere in this manual. These commands are provided here for
reference. (For commands that turn on debugging messages, see *Note
Debugging Output::.)
`maint agent EXPRESSION'
Translate the given EXPRESSION into remote agent bytecodes. This
command is useful for debugging the Agent Expression mechanism
(*note Agent Expressions::).
`maint info breakpoints'
Using the same format as `info breakpoints', display both the
breakpoints you've set explicitly, and those GDB is using for
internal purposes. Internal breakpoints are shown with negative
breakpoint numbers. The type column identifies what kind of
breakpoint is shown:
`breakpoint'
Normal, explicitly set breakpoint.
`watchpoint'
Normal, explicitly set watchpoint.
`longjmp'
Internal breakpoint, used to handle correctly stepping through
`longjmp' calls.
`longjmp resume'
Internal breakpoint at the target of a `longjmp'.
`until'
Temporary internal breakpoint used by the GDB `until' command.
`finish'
Temporary internal breakpoint used by the GDB `finish'
command.
`shlib events'
Shared library events.
`maint check-symtabs'
Check the consistency of psymtabs and symtabs.
`maint cplus first_component NAME'
Print the first C++ class/namespace component of NAME.
`maint cplus namespace'
Print the list of possible C++ namespaces.
`maint demangle NAME'
Demangle a C++ or Objective-C manled NAME.
`maint deprecate COMMAND [REPLACEMENT]'
`maint undeprecate COMMAND'
Deprecate or undeprecate the named COMMAND. Deprecated commands
cause GDB to issue a warning when you use them. The optional
argument REPLACEMENT says which newer command should be used in
favor of the deprecated one; if it is given, GDB will mention the
replacement as part of the warning.
`maint dump-me'
Cause a fatal signal in the debugger and force it to dump its core.
This is supported only on systems which support aborting a program
with the `SIGQUIT' signal.
`maint internal-error [MESSAGE-TEXT]'
`maint internal-warning [MESSAGE-TEXT]'
Cause GDB to call the internal function `internal_error' or
`internal_warning' and hence behave as though an internal error or
internal warning has been detected. In addition to reporting the
internal problem, these functions give the user the opportunity to
either quit GDB or create a core file of the current GDB session.
These commands take an optional parameter MESSAGE-TEXT that is
used as the text of the error or warning message.
Here's an example of using `indernal-error':
(gdb) maint internal-error testing, 1, 2
.../maint.c:121: internal-error: testing, 1, 2
A problem internal to GDB has been detected. Further
debugging may prove unreliable.
Quit this debugging session? (y or n) n
Create a core file? (y or n) n
(gdb)
`maint packet TEXT'
If GDB is talking to an inferior via the serial protocol, then
this command sends the string TEXT to the inferior, and displays
the response packet. GDB supplies the initial `$' character, the
terminating `#' character, and the checksum.
`maint print architecture [FILE]'
Print the entire architecture configuration. The optional argument
FILE names the file where the output goes.
`maint print dummy-frames'
Prints the contents of GDB's internal dummy-frame stack.
(gdb) b add
...
(gdb) print add(2,3)
Breakpoint 2, add (a=2, b=3) at ...
58 return (a + b);
The program being debugged stopped while in a function called from GDB.
...
(gdb) maint print dummy-frames
0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
top=0x0200bdd4 id={stack=0x200bddc,code=0x101405c}
call_lo=0x01014000 call_hi=0x01014001
(gdb)
Takes an optional file parameter.
`maint print registers [FILE]'
`maint print raw-registers [FILE]'
`maint print cooked-registers [FILE]'
`maint print register-groups [FILE]'
Print GDB's internal register data structures.
The command `maint print raw-registers' includes the contents of
the raw register cache; the command `maint print cooked-registers'
includes the (cooked) value of all registers; and the command
`maint print register-groups' includes the groups that each
register is a member of. *Note Registers: (gdbint)Registers.
These commands take an optional parameter, a file name to which to
write the information.
`maint print reggroups [FILE]'
Print GDB's internal register group data structures. The optional
argument FILE tells to what file to write the information.
The register groups info looks like this:
(gdb) maint print reggroups
Group Type
general user
float user
all user
vector user
system user
save internal
restore internal
`flushregs'
This command forces GDB to flush its internal register cache.
`maint print objfiles'
Print a dump of all known object files. For each object file, this
command prints its name, address in memory, and all of its psymtabs
and symtabs.
`maint print statistics'
This command prints, for each object file in the program, various
data about that object file followed by the byte cache ("bcache")
statistics for the object file. The objfile data includes the
number of minimal, partical, full, and stabs symbols, the number
of types defined by the objfile, the number of as yet unexpanded
psym tables, the number of line tables and string tables, and the
amount of memory used by the various tables. The bcache
statistics include the counts, sizes, and counts of duplicates of
all and unique objects, max, average, and median entry size, total
memory used and its overhead and savings, and various measures of
the hash table size and chain lengths.
`maint print type EXPR'
Print the type chain for a type specified by EXPR. The argument
can be either a type name or a symbol. If it is a symbol, the
type of that symbol is described. The type chain produced by this
command is a recursive definition of the data type as stored in
GDB's data structures, including its flags and contained types.
`maint set dwarf2 max-cache-age'
`maint show dwarf2 max-cache-age'
Control the DWARF 2 compilation unit cache.
In object files with inter-compilation-unit references, such as
those produced by the GCC option `-feliminate-dwarf2-dups', the
DWARF 2 reader needs to frequently refer to previously read
compilation units. This setting controls how long a compilation
unit will remain in the cache if it is not referenced. A higher
limit means that cached compilation units will be stored in memory
longer, and more total memory will be used. Setting it to zero
disables caching, which will slow down GDB startup, but reduce
memory consumption.
`maint set profile'
`maint show profile'
Control profiling of GDB.
Profiling will be disabled until you use the `maint set profile'
command to enable it. When you enable profiling, the system will
begin collecting timing and execution count data; when you disable
profiling or exit GDB, the results will be written to a log file.
Remember that if you use profiling, GDB will overwrite the
profiling log file (often called `gmon.out'). If you have a
record of important profiling data in a `gmon.out' file, be sure
to move it to a safe location.
Configuring with `--enable-profiling' arranges for GDB to be
compiled with the `-pg' compiler option.
`maint show-debug-regs'
Control whether to show variables that mirror the x86 hardware
debug registers. Use `ON' to enable, `OFF' to disable. If
enabled, the debug registers values are shown when GDB inserts or
removes a hardware breakpoint or watchpoint, and when the inferior
triggers a hardware-assisted breakpoint or watchpoint.
`maint space'
Control whether to display memory usage for each command. If set
to a nonzero value, GDB will display how much memory each command
took, following the command's own output. This can also be
requested by invoking GDB with the `--statistics' command-line
switch (*note Mode Options::).
`maint time'
Control whether to display the execution time for each command. If
set to a nonzero value, GDB will display how much time it took to
execute each command, following the command's own output. This
can also be requested by invoking GDB with the `--statistics'
command-line switch (*note Mode Options::).
`maint translate-address [SECTION] ADDR'
Find the symbol stored at the location specified by the address
ADDR and an optional section name SECTION. If found, GDB prints
the name of the closest symbol and an offset from the symbol's
location to the specified address. This is similar to the `info
address' command (*note Symbols::), except that this command also
allows to find symbols in other sections.
The following command is useful for non-interactive invocations of
GDB, such as in the test suite.
`set watchdog NSEC'
Set the maximum number of seconds GDB will wait for the target
operation to finish. If this time expires, GDB reports and error
and the command is aborted.
`show watchdog'
Show the current setting of the target wait timeout.

File: gdb.info, Node: Remote Protocol, Next: Agent Expressions, Prev: Maintenance Commands, Up: Top
Appendix D GDB Remote Serial Protocol
*************************************
* Menu:
* Overview::
* Packets::
* Stop Reply Packets::
* General Query Packets::
* Register Packet Format::
* Tracepoint Packets::
* Interrupts::
* Examples::
* File-I/O remote protocol extension::
* Memory map format::

File: gdb.info, Node: Overview, Next: Packets, Up: Remote Protocol
D.1 Overview
============
There may be occasions when you need to know something about the
protocol--for example, if there is only one serial port to your target
machine, you might want your program to do something special if it
recognizes a packet meant for GDB.
In the examples below, `->' and `<-' are used to indicate
transmitted and received data respectfully.
All GDB commands and responses (other than acknowledgments) are sent
as a PACKET. A PACKET is introduced with the character `$', the actual
PACKET-DATA, and the terminating character `#' followed by a two-digit
CHECKSUM:
`$'PACKET-DATA`#'CHECKSUM
The two-digit CHECKSUM is computed as the modulo 256 sum of all
characters between the leading `$' and the trailing `#' (an eight bit
unsigned checksum).
Implementors should note that prior to GDB 5.0 the protocol
specification also included an optional two-digit SEQUENCE-ID:
`$'SEQUENCE-ID`:'PACKET-DATA`#'CHECKSUM
That SEQUENCE-ID was appended to the acknowledgment. GDB has never
output SEQUENCE-IDs. Stubs that handle packets added since GDB 5.0
must not accept SEQUENCE-ID.
When either the host or the target machine receives a packet, the
first response expected is an acknowledgment: either `+' (to indicate
the package was received correctly) or `-' (to request retransmission):
-> `$'PACKET-DATA`#'CHECKSUM
<- `+'
The host (GDB) sends COMMANDs, and the target (the debugging stub
incorporated in your program) sends a RESPONSE. In the case of step
and continue COMMANDs, the response is only sent when the operation has
completed (the target has again stopped).
PACKET-DATA consists of a sequence of characters with the exception
of `#' and `$' (see `X' packet for additional exceptions).
Fields within the packet should be separated using `,' `;' or `:'.
Except where otherwise noted all numbers are represented in HEX with
leading zeros suppressed.
Implementors should note that prior to GDB 5.0, the character `:'
could not appear as the third character in a packet (as it would
potentially conflict with the SEQUENCE-ID).
Binary data in most packets is encoded either as two hexadecimal
digits per byte of binary data. This allowed the traditional remote
protocol to work over connections which were only seven-bit clean.
Some packets designed more recently assume an eight-bit clean
connection, and use a more efficient encoding to send and receive
binary data.
The binary data representation uses `7d' (ASCII `}') as an escape
character. Any escaped byte is transmitted as the escape character
followed by the original character XORed with `0x20'. For example, the
byte `0x7d' would be transmitted as the two bytes `0x7d 0x5d'. The
bytes `0x23' (ASCII `#'), `0x24' (ASCII `$'), and `0x7d' (ASCII `}')
must always be escaped. Responses sent by the stub must also escape
`0x2a' (ASCII `*'), so that it is not interpreted as the start of a
run-length encoded sequence (described next).
Response DATA can be run-length encoded to save space. A `*' means
that the next character is an ASCII encoding giving a repeat count
which stands for that many repetitions of the character preceding the
`*'. The encoding is `n+29', yielding a printable character where `n
>=3' (which is where rle starts to win). The printable characters `$',
`#', `+' and `-' or with a numeric value greater than 126 should not be
used.
So:
"`0* '"
means the same as "0000".
The error response returned for some packets includes a two character
error number. That number is not well defined.
For any COMMAND not supported by the stub, an empty response
(`$#00') should be returned. That way it is possible to extend the
protocol. A newer GDB can tell if a packet is supported based on that
response.
A stub is required to support the `g', `G', `m', `M', `c', and `s'
COMMANDs. All other COMMANDs are optional.

File: gdb.info, Node: Packets, Next: Stop Reply Packets, Prev: Overview, Up: Remote Protocol
D.2 Packets
===========
The following table provides a complete list of all currently defined
COMMANDs and their corresponding response DATA. *Note File-I/O remote
protocol extension::, for details about the File I/O extension of the
remote protocol.
Each packet's description has a template showing the packet's overall
syntax, followed by an explanation of the packet's meaning. We include
spaces in some of the templates for clarity; these are not part of the
packet's syntax. No GDB packet uses spaces to separate its components.
For example, a template like `foo BAR BAZ' describes a packet
beginning with the three ASCII bytes `foo', followed by a BAR, followed
directly by a BAZ. GDB does not transmit a space character between the
`foo' and the BAR, or between the BAR and the BAZ.
Note that all packet forms beginning with an upper- or lower-case
letter, other than those described here, are reserved for future use.
Here are the packet descriptions.
`!'
Enable extended mode. In extended mode, the remote server is made
persistent. The `R' packet is used to restart the program being
debugged.
Reply:
`OK'
The remote target both supports and has enabled extended mode.
`?'
Indicate the reason the target halted. The reply is the same as
for step and continue.
Reply: *Note Stop Reply Packets::, for the reply specifications.
`A ARGLEN,ARGNUM,ARG,...'
Initialized `argv[]' array passed into program. ARGLEN specifies
the number of bytes in the hex encoded byte stream ARG. See
`gdbserver' for more details.
Reply:
`OK'
The arguments were set.
`E NN'
An error occurred.
`b BAUD'
(Don't use this packet; its behavior is not well-defined.) Change
the serial line speed to BAUD.
JTC: _When does the transport layer state change? When it's
received, or after the ACK is transmitted. In either case, there
are problems if the command or the acknowledgment packet is
dropped._
Stan: _If people really wanted to add something like this, and get
it working for the first time, they ought to modify ser-unix.c to
send some kind of out-of-band message to a specially-setup stub
and have the switch happen "in between" packets, so that from
remote protocol's point of view, nothing actually happened._
`B ADDR,MODE'
Set (MODE is `S') or clear (MODE is `C') a breakpoint at ADDR.
Don't use this packet. Use the `Z' and `z' packets instead (*note
insert breakpoint or watchpoint packet::).
`c [ADDR]'
Continue. ADDR is address to resume. If ADDR is omitted, resume
at current address.
Reply: *Note Stop Reply Packets::, for the reply specifications.
`C SIG[;ADDR]'
Continue with signal SIG (hex signal number). If `;ADDR' is
omitted, resume at same address.
Reply: *Note Stop Reply Packets::, for the reply specifications.
`d'
Toggle debug flag.
Don't use this packet; instead, define a general set packet (*note
General Query Packets::).
`D'
Detach GDB from the remote system. Sent to the remote target
before GDB disconnects via the `detach' command.
Reply:
`OK'
for success
`E NN'
for an error
`F RC,EE,CF;XX'
A reply from GDB to an `F' packet sent by the target. This is
part of the File-I/O protocol extension. *Note File-I/O remote
protocol extension::, for the specification.
`g'
Read general registers.
Reply:
`XX...'
Each byte of register data is described by two hex digits.
The bytes with the register are transmitted in target byte
order. The size of each register and their position within
the `g' packet are determined by the GDB internal macros
`DEPRECATED_REGISTER_RAW_SIZE' and `REGISTER_NAME' macros.
The specification of several standard `g' packets is
specified below.
`E NN'
for an error.
`G XX...'
Write general registers. *Note read registers packet::, for a
description of the XX... data.
Reply:
`OK'
for success
`E NN'
for an error
`H C T'
Set thread for subsequent operations (`m', `M', `g', `G', et.al.).
C depends on the operation to be performed: it should be `c' for
step and continue operations, `g' for other operations. The
thread designator T may be `-1', meaning all the threads, a thread
number, or `0' which means pick any thread.
Reply:
`OK'
for success
`E NN'
for an error
`i [ADDR[,NNN]]'
Step the remote target by a single clock cycle. If `,NNN' is
present, cycle step NNN cycles. If ADDR is present, cycle step
starting at that address.
`I'
Signal, then cycle step. *Note step with signal packet::. *Note
cycle step packet::.
`k'
Kill request.
FIXME: _There is no description of how to operate when a specific
thread context has been selected (i.e. does 'k' kill only that
thread?)_.
`m ADDR,LENGTH'
Read LENGTH bytes of memory starting at address ADDR. Note that
ADDR may not be aligned to any particular boundary.
The stub need not use any particular size or alignment when
gathering data from memory for the response; even if ADDR is
word-aligned and LENGTH is a multiple of the word size, the stub
is free to use byte accesses, or not. For this reason, this
packet may not be suitable for accessing memory-mapped I/O devices.
Reply:
`XX...'
Memory contents; each byte is transmitted as a two-digit
hexadecimal number. The reply may contain fewer bytes than
requested if the server was able to read only part of the
region of memory.
`E NN'
NN is errno
`M ADDR,LENGTH:XX...'
Write LENGTH bytes of memory starting at address ADDR. XX... is
the data; each byte is transmitted as a two-digit hexadecimal
number.
Reply:
`OK'
for success
`E NN'
for an error (this includes the case where only part of the
data was written).
`p N'
Read the value of register N; N is in hex. *Note read registers
packet::, for a description of how the returned register value is
encoded.
Reply:
`XX...'
the register's value
`E NN'
for an error
`'
Indicating an unrecognized QUERY.
`P N...=R...'
Write register N... with value R.... The register number N is in
hexadecimal, and R... contains two hex digits for each byte in the
register (target byte order).
Reply:
`OK'
for success
`E NN'
for an error
`q NAME PARAMS...'
`Q NAME PARAMS...'
General query (`q') and set (`Q'). These packets are described
fully in *Note General Query Packets::.
`r'
Reset the entire system.
Don't use this packet; use the `R' packet instead.
`R XX'
Restart the program being debugged. XX, while needed, is ignored.
This packet is only available in extended mode.
The `R' packet has no reply.
`s [ADDR]'
Single step. ADDR is the address at which to resume. If ADDR is
omitted, resume at same address.
Reply: *Note Stop Reply Packets::, for the reply specifications.
`S SIG[;ADDR]'
Step with signal. This is analogous to the `C' packet, but
requests a single-step, rather than a normal resumption of
execution.
Reply: *Note Stop Reply Packets::, for the reply specifications.
`t ADDR:PP,MM'
Search backwards starting at address ADDR for a match with pattern
PP and mask MM. PP and MM are 4 bytes. ADDR must be at least 3
digits.
`T XX'
Find out if the thread XX is alive.
Reply:
`OK'
thread is still alive
`E NN'
thread is dead
`v'
Packets starting with `v' are identified by a multi-letter name,
up to the first `;' or `?' (or the end of the packet).
`vCont[;ACTION[:TID]]...'
Resume the inferior, specifying different actions for each thread.
If an action is specified with no TID, then it is applied to any
threads that don't have a specific action specified; if no default
action is specified then other threads should remain stopped.
Specifying multiple default actions is an error; specifying no
actions is also an error. Thread IDs are specified in
hexadecimal. Currently supported actions are:
`c'
Continue.
`C SIG'
Continue with signal SIG. SIG should be two hex digits.
`s'
Step.
`S SIG'
Step with signal SIG. SIG should be two hex digits.
The optional ADDR argument normally associated with these packets
is not supported in `vCont'.
Reply: *Note Stop Reply Packets::, for the reply specifications.
`vCont?'
Request a list of actions supporetd by the `vCont' packet.
Reply:
`vCont[;ACTION...]'
The `vCont' packet is supported. Each ACTION is a supported
command in the `vCont' packet.
`'
The `vCont' packet is not supported.
`vFlashErase:ADDR,LENGTH'
Direct the stub to erase LENGTH bytes of flash starting at ADDR.
The region may enclose any number of flash blocks, but its start
and end must fall on block boundaries, as indicated by the flash
block size appearing in the memory map (*note Memory map
format::). GDB groups flash memory programming operations
together, and sends a `vFlashDone' request after each group; the
stub is allowed to delay erase operation until the `vFlashDone'
packet is received.
Reply:
`OK'
for success
`E NN'
for an error
`vFlashWrite:ADDR:XX...'
Direct the stub to write data to flash address ADDR. The data is
passed in binary form using the same encoding as for the `X'
packet (*note Binary Data::). The memory ranges specified by
`vFlashWrite' packets preceding a `vFlashDone' packet must not
overlap, and must appear in order of increasing addresses
(although `vFlashErase' packets for higher addresses may already
have been received; the ordering is guaranteed only between
`vFlashWrite' packets). If a packet writes to an address that was
neither erased by a preceding `vFlashErase' packet nor by some
other target-specific method, the results are unpredictable.
Reply:
`OK'
for success
`E.memtype'
for vFlashWrite addressing non-flash memory
`E NN'
for an error
`vFlashDone'
Indicate to the stub that flash programming operation is finished.
The stub is permitted to delay or batch the effects of a group of
`vFlashErase' and `vFlashWrite' packets until a `vFlashDone'
packet is received. The contents of the affected regions of flash
memory are unpredictable until the `vFlashDone' request is
completed.
`X ADDR,LENGTH:XX...'
Write data to memory, where the data is transmitted in binary.
ADDR is address, LENGTH is number of bytes, `XX...' is binary data
(*note Binary Data::).
Reply:
`OK'
for success
`E NN'
for an error
`z TYPE,ADDR,LENGTH'
`Z TYPE,ADDR,LENGTH'
Insert (`Z') or remove (`z') a TYPE breakpoint or watchpoint
starting at address ADDRESS and covering the next LENGTH bytes.
Each breakpoint and watchpoint packet TYPE is documented
separately.
_Implementation notes: A remote target shall return an empty string
for an unrecognized breakpoint or watchpoint packet TYPE. A
remote target shall support either both or neither of a given
`ZTYPE...' and `zTYPE...' packet pair. To avoid potential
problems with duplicate packets, the operations should be
implemented in an idempotent way._
`z0,ADDR,LENGTH'
`Z0,ADDR,LENGTH'
Insert (`Z0') or remove (`z0') a memory breakpoint at address ADDR
of size LENGTH.
A memory breakpoint is implemented by replacing the instruction at
ADDR with a software breakpoint or trap instruction. The LENGTH
is used by targets that indicates the size of the breakpoint (in
bytes) that should be inserted (e.g., the ARM and MIPS can insert
either a 2 or 4 byte breakpoint).
_Implementation note: It is possible for a target to copy or move
code that contains memory breakpoints (e.g., when implementing
overlays). The behavior of this packet, in the presence of such a
target, is not defined._
Reply:
`OK'
success
`'
not supported
`E NN'
for an error
`z1,ADDR,LENGTH'
`Z1,ADDR,LENGTH'
Insert (`Z1') or remove (`z1') a hardware breakpoint at address
ADDR of size LENGTH.
A hardware breakpoint is implemented using a mechanism that is not
dependant on being able to modify the target's memory.
_Implementation note: A hardware breakpoint is not affected by code
movement._
Reply:
`OK'
success
`'
not supported
`E NN'
for an error
`z2,ADDR,LENGTH'
`Z2,ADDR,LENGTH'
Insert (`Z2') or remove (`z2') a write watchpoint.
Reply:
`OK'
success
`'
not supported
`E NN'
for an error
`z3,ADDR,LENGTH'
`Z3,ADDR,LENGTH'
Insert (`Z3') or remove (`z3') a read watchpoint.
Reply:
`OK'
success
`'
not supported
`E NN'
for an error
`z4,ADDR,LENGTH'
`Z4,ADDR,LENGTH'
Insert (`Z4') or remove (`z4') an access watchpoint.
Reply:
`OK'
success
`'
not supported
`E NN'
for an error

File: gdb.info, Node: Stop Reply Packets, Next: General Query Packets, Prev: Packets, Up: Remote Protocol
D.3 Stop Reply Packets
======================
The `C', `c', `S', `s' and `?' packets can receive any of the below as
a reply. In the case of the `C', `c', `S' and `s' packets, that reply
is only returned when the target halts. In the below the exact meaning
of "signal number" is poorly defined. In general one of the UNIX signal
numbering conventions is used.
As in the description of request packets, we include spaces in the
reply templates for clarity; these are not part of the reply packet's
syntax. No GDB stop reply packet uses spaces to separate its
components.
`S AA'
The program received signal number AA (a two-digit hexadecimal
number). This is equivalent to a `T' response with no N:R pairs.
`T AA N1:R1;N2:R2;...'
The program received signal number AA (a two-digit hexadecimal
number). This is equivalent to an `S' response, except that the
`N:R' pairs can carry values of important registers and other
information directly in the stop reply packet, reducing round-trip
latency. Single-step and breakpoint traps are reported this way.
Each `N:R' pair is interpreted as follows:
1. If N is a hexadecimal number, it is a register number, and the
corresponding R gives that register's value. R is a series
of bytes in target byte order, with each byte given by a
two-digit hex number.
2. If N is `thread', then R is the thread process ID, in hex.
3. If N is `watch', `rwatch', or `awatch', then the packet
indicates a watchpoint hit, and R is the data address, in hex.
4. Otherwise, GDB should ignore this `N:R' pair and go on to the
next; this allows us to extend the protocol in the future.
`W AA'
The process exited, and AA is the exit status. This is only
applicable to certain targets.
`X AA'
The process terminated with signal AA.
`O XX...'
`XX...' is hex encoding of ASCII data, to be written as the
program's console output. This can happen at any time while the
program is running and the debugger should continue to wait for
`W', `T', etc.
`F CALL-ID,PARAMETER...'
CALL-ID is the identifier which says which host system call should
be called. This is just the name of the function. Translation
into the correct system call is only applicable as it's defined in
GDB. *Note File-I/O remote protocol extension::, for a list of
implemented system calls.
`PARAMETER...' is a list of parameters as defined for this very
system call.
The target replies with this packet when it expects GDB to call a
host system call on behalf of the target. GDB replies with an
appropriate `F' packet and keeps up waiting for the next reply
packet from the target. The latest `C', `c', `S' or `s' action is
expected to be continued. *Note File-I/O remote protocol
extension::, for more details.

File: gdb.info, Node: General Query Packets, Next: Register Packet Format, Prev: Stop Reply Packets, Up: Remote Protocol
D.4 General Query Packets
=========================
Packets starting with `q' are "general query packets"; packets starting
with `Q' are "general set packets". General query and set packets are
a semi-unified form for retrieving and sending information to and from
the stub.
The initial letter of a query or set packet is followed by a name
indicating what sort of thing the packet applies to. For example, GDB
may use a `qSymbol' packet to exchange symbol definitions with the
stub. These packet names follow some conventions:
* The name must not contain commas, colons or semicolons.
* Most GDB query and set packets have a leading upper case letter.
* The names of custom vendor packets should use a company prefix, in
lower case, followed by a period. For example, packets designed at
the Acme Corporation might begin with `qacme.foo' (for querying
foos) or `Qacme.bar' (for setting bars).
The name of a query or set packet should be separated from any
parameters by a `:'; the parameters themselves should be separated by
`,' or `;'. Stubs must be careful to match the full packet name, and
check for a separator or the end of the packet, in case two packet
names share a common prefix. New packets should not begin with `qC',
`qP', or `qL'(1).
Like the descriptions of the other packets, each description here
has a template showing the packet's overall syntax, followed by an
explanation of the packet's meaning. We include spaces in some of the
templates for clarity; these are not part of the packet's syntax. No
GDB packet uses spaces to separate its components.
Here are the currently defined query and set packets:
`qC'
Return the current thread id.
Reply:
`QC PID'
Where PID is an unsigned hexadecimal process id.
`(anything else)'
Any other reply implies the old pid.
`qCRC:ADDR,LENGTH'
Compute the CRC checksum of a block of memory. Reply:
`E NN'
An error (such as memory fault)
`C CRC32'
The specified memory region's checksum is CRC32.
`qfThreadInfo'
`qsThreadInfo'
Obtain a list of all active thread ids from the target (OS).
Since there may be too many active threads to fit into one reply
packet, this query works iteratively: it may require more than one
query/reply sequence to obtain the entire list of threads. The
first query of the sequence will be the `qfThreadInfo' query;
subsequent queries in the sequence will be the `qsThreadInfo'
query.
NOTE: This packet replaces the `qL' query (see below).
Reply:
`m ID'
A single thread id
`m ID,ID...'
a comma-separated list of thread ids
`l'
(lower case letter `L') denotes end of list.
In response to each query, the target will reply with a list of
one or more thread ids, in big-endian unsigned hex, separated by
commas. GDB will respond to each reply with a request for more
thread ids (using the `qs' form of the query), until the target
responds with `l' (lower-case el, for "last").
`qGetTLSAddr:THREAD-ID,OFFSET,LM'
Fetch the address associated with thread local storage specified
by THREAD-ID, OFFSET, and LM.
THREAD-ID is the (big endian, hex encoded) thread id associated
with the thread for which to fetch the TLS address.
OFFSET is the (big endian, hex encoded) offset associated with the
thread local variable. (This offset is obtained from the debug
information associated with the variable.)
LM is the (big endian, hex encoded) OS/ABI specific encoding of the
the load module associated with the thread local storage. For
example, a GNU/Linux system will pass the link map address of the
shared object associated with the thread local storage under
consideration. Other operating environments may choose to
represent the load module differently, so the precise meaning of
this parameter will vary.
Reply:
`XX...'
Hex encoded (big endian) bytes representing the address of
the thread local storage requested.
`E NN'
An error occurred. NN are hex digits.
`'
An empty reply indicates that `qGetTLSAddr' is not supported
by the stub.
`qL STARTFLAG THREADCOUNT NEXTTHREAD'
Obtain thread information from RTOS. Where: STARTFLAG (one hex
digit) is one to indicate the first query and zero to indicate a
subsequent query; THREADCOUNT (two hex digits) is the maximum
number of threads the response packet can contain; and NEXTTHREAD
(eight hex digits), for subsequent queries (STARTFLAG is zero), is
returned in the response as ARGTHREAD.
Don't use this packet; use the `qfThreadInfo' query instead (see
above).
Reply:
`qM COUNT DONE ARGTHREAD THREAD...'
Where: COUNT (two hex digits) is the number of threads being
returned; DONE (one hex digit) is zero to indicate more
threads and one indicates no further threads; ARGTHREADID
(eight hex digits) is NEXTTHREAD from the request packet;
THREAD... is a sequence of thread IDs from the target.
THREADID (eight hex digits). See
`remote.c:parse_threadlist_response()'.
`qOffsets'
Get section offsets that the target used when re-locating the
downloaded image. _Note: while a `Bss' offset is included in the
response, GDB ignores this and instead applies the `Data' offset
to the `Bss' section._
Reply:
`Text=XXX;Data=YYY;Bss=ZZZ'
`qP MODE THREADID'
Returns information on THREADID. Where: MODE is a hex encoded 32
bit mode; THREADID is a hex encoded 64 bit thread ID.
Don't use this packet; use the `qThreadExtraInfo' query instead
(see below).
Reply: see `remote.c:remote_unpack_thread_info_response()'.
`qRcmd,COMMAND'
COMMAND (hex encoded) is passed to the local interpreter for
execution. Invalid commands should be reported using the output
string. Before the final result packet, the target may also
respond with a number of intermediate `OOUTPUT' console output
packets. _Implementors should note that providing access to a
stubs's interpreter may have security implications_.
Reply:
`OK'
A command response with no output.
`OUTPUT'
A command response with the hex encoded output string OUTPUT.
`E NN'
Indicate a badly formed request.
`'
An empty reply indicates that `qRcmd' is not recognized.
(Note that the `qRcmd' packet's name is separated from the command
by a `,', not a `:', contrary to the naming conventions above.
Please don't use this packet as a model for new packets.)
`qSupported [:GDBFEATURE [;GDBFEATURE]... ]'
Tell the remote stub about features supported by GDB, and query
the stub for features it supports. This packet allows GDB and the
remote stub to take advantage of each others' features.
`qSupported' also consolidates multiple feature probes at startup,
to improve GDB performance--a single larger packet performs better
than multiple smaller probe packets on high-latency links. Some
features may enable behavior which must not be on by default, e.g.
because it would confuse older clients or stubs. Other features
may describe packets which could be automatically probed for, but
are not. These features must be reported before GDB will use
them. This "default unsupported" behavior is not appropriate for
all packets, but it helps to keep the initial connection time
under control with new versions of GDB which support increasing
numbers of packets.
Reply:
`STUBFEATURE [;STUBFEATURE]...'
The stub supports or does not support each returned
STUBFEATURE, depending on the form of each STUBFEATURE (see
below for the possible forms).
`'
An empty reply indicates that `qSupported' is not recognized,
or that no features needed to be reported to GDB.
The allowed forms for each feature (either a GDBFEATURE in the
`qSupported' packet, or a STUBFEATURE in the response) are:
`NAME=VALUE'
The remote protocol feature NAME is supported, and associated
with the specified VALUE. The format of VALUE depends on the
feature, but it must not include a semicolon.
`NAME+'
The remote protocol feature NAME is supported, and does not
need an associated value.
`NAME-'
The remote protocol feature NAME is not supported.
`NAME?'
The remote protocol feature NAME may be supported, and GDB
should auto-detect support in some other way when it is
needed. This form will not be used for GDBFEATURE
notifications, but may be used for STUBFEATURE responses.
Whenever the stub receives a `qSupported' request, the supplied
set of GDB features should override any previous request. This
allows GDB to put the stub in a known state, even if the stub had
previously been communicating with a different version of GDB.
No values of GDBFEATURE (for the packet sent by GDB) are defined
yet. Stubs should ignore any unknown values for GDBFEATURE. Any
GDB which sends a `qSupported' packet supports receiving packets
of unlimited length (earlier versions of GDB may reject overly
long responses). Values for GDBFEATURE may be defined in the
future to let the stub take advantage of new features in GDB, e.g.
incompatible improvements in the remote protocol--support for
unlimited length responses would be a GDBFEATURE example, if it
were not implied by the `qSupported' query. The stub's reply
should be independent of the GDBFEATURE entries sent by GDB; first
GDB describes all the features it supports, and then the stub
replies with all the features it supports.
Similarly, GDB will silently ignore unrecognized stub feature
responses, as long as each response uses one of the standard forms.
Some features are flags. A stub which supports a flag feature
should respond with a `+' form response. Other features require
values, and the stub should respond with an `=' form response.
Each feature has a default value, which GDB will use if
`qSupported' is not available or if the feature is not mentioned
in the `qSupported' response. The default values are fixed; a
stub is free to omit any feature responses that match the defaults.
Not all features can be probed, but for those which can, the
probing mechanism is useful: in some cases, a stub's internal
architecture may not allow the protocol layer to know some
information about the underlying target in advance. This is
especially common in stubs which may be configured for multiple
targets.
These are the currently defined stub features and their properties:
Feature Name Value Default Probe Allowed
Required
`PacketSize' Yes `-' No
`qXfer:auxv:read' No `-' Yes
`qXfer:memory-map:read'No `-' Yes
These are the currently defined stub features, in more detail:
`PacketSize=BYTES'
The remote stub can accept packets up to at least BYTES in
length. GDB will send packets up to this size for bulk
transfers, and will never send larger packets. This is a
limit on the data characters in the packet, including the
frame and checksum. There is no trailing NUL byte in a
remote protocol packet; if the stub stores packets in a
NUL-terminated format, it should allow an extra byte in its
buffer for the NUL. If this stub feature is not supported,
GDB guesses based on the size of the `g' packet response.
`qXfer:auxv:read'
The remote stub understands the `qXfer:auxv:read' packet
(*note qXfer auxiliary vector read::).
`qSymbol::'
Notify the target that GDB is prepared to serve symbol lookup
requests. Accept requests from the target for the values of
symbols.
Reply:
`OK'
The target does not need to look up any (more) symbols.
`qSymbol:SYM_NAME'
The target requests the value of symbol SYM_NAME (hex
encoded). GDB may provide the value by using the
`qSymbol:SYM_VALUE:SYM_NAME' message, described below.
`qSymbol:SYM_VALUE:SYM_NAME'
Set the value of SYM_NAME to SYM_VALUE.
SYM_NAME (hex encoded) is the name of a symbol whose value the
target has previously requested.
SYM_VALUE (hex) is the value for symbol SYM_NAME. If GDB cannot
supply a value for SYM_NAME, then this field will be empty.
Reply:
`OK'
The target does not need to look up any (more) symbols.
`qSymbol:SYM_NAME'
The target requests the value of a new symbol SYM_NAME (hex
encoded). GDB will continue to supply the values of symbols
(if available), until the target ceases to request them.
`QTDP'
`QTFrame'
*Note Tracepoint Packets::.
`qThreadExtraInfo,ID'
Obtain a printable string description of a thread's attributes from
the target OS. ID is a thread-id in big-endian hex. This string
may contain anything that the target OS thinks is interesting for
GDB to tell the user about the thread. The string is displayed in
GDB's `info threads' display. Some examples of possible thread
extra info strings are `Runnable', or `Blocked on Mutex'.
Reply:
`XX...'
Where `XX...' is a hex encoding of ASCII data, comprising the
printable string containing the extra information about the
thread's attributes.
(Note that the `qThreadExtraInfo' packet's name is separated from
the command by a `,', not a `:', contrary to the naming
conventions above. Please don't use this packet as a model for new
packets.)
`QTStart'
`QTStop'
`QTinit'
`QTro'
`qTStatus'
*Note Tracepoint Packets::.
`qXfer:OBJECT:read:ANNEX:OFFSET,LENGTH'
Read uninterpreted bytes from the target's special data area
identified by the keyword OBJECT. Request LENGTH bytes starting
at OFFSET bytes into the data. The content and encoding of ANNEX
is specific to the object; it can supply additional details about
what data to access.
Here are the specific requests of this form defined so far. All
`qXfer:OBJECT:read:...' requests use the same reply formats,
listed below.
`qXfer:auxv:read::OFFSET,LENGTH'
Access the target's "auxiliary vector". *Note auxiliary
vector: OS Information. Note ANNEX must be empty.
This packet is not probed by default; the remote stub must
request it, by suppling an appropriate `qSupported' response
(*note qSupported::).
`qXfer:memory-map:read::OFFSET,LENGTH'
Access the target's "memory-map". *Note Memory map format::.
The annex part of the generic `qXfer' packet must be empty
(*note qXfer read::).
This packet is not probed by default; the remote stub must
request it, by supplying an appropriate `qSupported' response
(*note qSupported::).
Reply:
`m DATA'
Data DATA (*note Binary Data::) has been read from the
target. There may be more data at a higher address (although
it is permitted to return `m' even for the last valid block
of data, as long as at least one byte of data was read).
DATA may have fewer bytes than the LENGTH in the request.
`l DATA'
Data DATA (*note Binary Data::) has been read from the target.
There is no more data to be read. DATA may have fewer bytes
than the LENGTH in the request.
`l'
The OFFSET in the request is at the end of the data. There
is no more data to be read.
`E00'
The request was malformed, or ANNEX was invalid.
`E NN'
The offset was invalid, or there was an error encountered
reading the data. NN is a hex-encoded `errno' value.
`'
An empty reply indicates the OBJECT string was not recognized
by the stub, or that the object does not support reading.
`qXfer:OBJECT:write:ANNEX:OFFSET:DATA...'
Write uninterpreted bytes into the target's special data area
identified by the keyword OBJECT, starting at OFFSET bytes into
the data. `DATA...' is the binary-encoded data (*note Binary
Data::) to be written. The content and encoding of ANNEX is
specific to the object; it can supply additional details about
what data to access.
No requests of this form are presently in use. This specification
serves as a placeholder to document the common format that new
specific request specifications ought to use.
Reply:
`NN'
NN (hex encoded) is the number of bytes written. This may be
fewer bytes than supplied in the request.
`E00'
The request was malformed, or ANNEX was invalid.
`E NN'
The offset was invalid, or there was an error encountered
writing the data. NN is a hex-encoded `errno' value.
`'
An empty reply indicates the OBJECT string was not recognized
by the stub, or that the object does not support writing.
`qXfer:OBJECT:OPERATION:...'
Requests of this form may be added in the future. When a stub does
not recognize the OBJECT keyword, or its support for OBJECT does
not recognize the OPERATION keyword, the stub must respond with an
empty packet.
---------- Footnotes ----------
(1) The `qP' and `qL' packets predate these conventions, and have
arguments without any terminator for the packet name; we suspect they
are in widespread use in places that are difficult to upgrade. The
`qC' packet has no arguments, but some existing stubs (e.g. RedBoot)
are known to not check for the end of the packet.

File: gdb.info, Node: Register Packet Format, Next: Tracepoint Packets, Prev: General Query Packets, Up: Remote Protocol
D.5 Register Packet Format
==========================
The following `g'/`G' packets have previously been defined. In the
below, some thirty-two bit registers are transferred as sixty-four
bits. Those registers should be zero/sign extended (which?) to fill
the space allocated. Register bytes are transferred in target byte
order. The two nibbles within a register byte are transferred
most-significant - least-significant.
MIPS32
All registers are transferred as thirty-two bit quantities in the
order: 32 general-purpose; sr; lo; hi; bad; cause; pc; 32
floating-point registers; fsr; fir; fp.
MIPS64
All registers are transferred as sixty-four bit quantities
(including thirty-two bit registers such as `sr'). The ordering
is the same as `MIPS32'.

File: gdb.info, Node: Tracepoint Packets, Next: Interrupts, Prev: Register Packet Format, Up: Remote Protocol
D.6 Tracepoint Packets
======================
Here we describe the packets GDB uses to implement tracepoints (*note
Tracepoints::).
`QTDP:N:ADDR:ENA:STEP:PASS[-]'
Create a new tracepoint, number N, at ADDR. If ENA is `E', then
the tracepoint is enabled; if it is `D', then the tracepoint is
disabled. STEP is the tracepoint's step count, and PASS is its
pass count. If the trailing `-' is present, further `QTDP'
packets will follow to specify this tracepoint's actions.
Replies:
`OK'
The packet was understood and carried out.
`'
The packet was not recognized.
`QTDP:-N:ADDR:[S]ACTION...[-]'
Define actions to be taken when a tracepoint is hit. N and ADDR
must be the same as in the initial `QTDP' packet for this
tracepoint. This packet may only be sent immediately after
another `QTDP' packet that ended with a `-'. If the trailing `-'
is present, further `QTDP' packets will follow, specifying more
actions for this tracepoint.
In the series of action packets for a given tracepoint, at most one
can have an `S' before its first ACTION. If such a packet is
sent, it and the following packets define "while-stepping"
actions. Any prior packets define ordinary actions -- that is,
those taken when the tracepoint is first hit. If no action packet
has an `S', then all the packets in the series specify ordinary
tracepoint actions.
The `ACTION...' portion of the packet is a series of actions,
concatenated without separators. Each action has one of the
following forms:
`R MASK'
Collect the registers whose bits are set in MASK. MASK is a
hexadecimal number whose I'th bit is set if register number I
should be collected. (The least significant bit is numbered
zero.) Note that MASK may be any number of digits long; it
may not fit in a 32-bit word.
`M BASEREG,OFFSET,LEN'
Collect LEN bytes of memory starting at the address in
register number BASEREG, plus OFFSET. If BASEREG is `-1',
then the range has a fixed address: OFFSET is the address of
the lowest byte to collect. The BASEREG, OFFSET, and LEN
parameters are all unsigned hexadecimal values (the `-1'
value for BASEREG is a special case).
`X LEN,EXPR'
Evaluate EXPR, whose length is LEN, and collect memory as it
directs. EXPR is an agent expression, as described in *Note
Agent Expressions::. Each byte of the expression is encoded
as a two-digit hex number in the packet; LEN is the number of
bytes in the expression (and thus one-half the number of hex
digits in the packet).
Any number of actions may be packed together in a single `QTDP'
packet, as long as the packet does not exceed the maximum packet
length (400 bytes, for many stubs). There may be only one `R'
action per tracepoint, and it must precede any `M' or `X' actions.
Any registers referred to by `M' and `X' actions must be
collected by a preceding `R' action. (The "while-stepping"
actions are treated as if they were attached to a separate
tracepoint, as far as these restrictions are concerned.)
Replies:
`OK'
The packet was understood and carried out.
`'
The packet was not recognized.
`QTFrame:N'
Select the N'th tracepoint frame from the buffer, and use the
register and memory contents recorded there to answer subsequent
request packets from GDB.
A successful reply from the stub indicates that the stub has found
the requested frame. The response is a series of parts,
concatenated without separators, describing the frame we selected.
Each part has one of the following forms:
`F F'
The selected frame is number N in the trace frame buffer; F
is a hexadecimal number. If F is `-1', then there was no
frame matching the criteria in the request packet.
`T T'
The selected trace frame records a hit of tracepoint number T;
T is a hexadecimal number.
`QTFrame:pc:ADDR'
Like `QTFrame:N', but select the first tracepoint frame after the
currently selected frame whose PC is ADDR; ADDR is a hexadecimal
number.
`QTFrame:tdp:T'
Like `QTFrame:N', but select the first tracepoint frame after the
currently selected frame that is a hit of tracepoint T; T is a
hexadecimal number.
`QTFrame:range:START:END'
Like `QTFrame:N', but select the first tracepoint frame after the
currently selected frame whose PC is between START (inclusive) and
END (exclusive); START and END are hexadecimal numbers.
`QTFrame:outside:START:END'
Like `QTFrame:range:START:END', but select the first frame
_outside_ the given range of addresses.
`QTStart'
Begin the tracepoint experiment. Begin collecting data from
tracepoint hits in the trace frame buffer.
`QTStop'
End the tracepoint experiment. Stop collecting trace frames.
`QTinit'
Clear the table of tracepoints, and empty the trace frame buffer.
`QTro:START1,END1:START2,END2:...'
Establish the given ranges of memory as "transparent". The stub
will answer requests for these ranges from memory's current
contents, if they were not collected as part of the tracepoint hit.
GDB uses this to mark read-only regions of memory, like those
containing program code. Since these areas never change, they
should still have the same contents they did when the tracepoint
was hit, so there's no reason for the stub to refuse to provide
their contents.
`qTStatus'
Ask the stub if there is a trace experiment running right now.
Replies:
`T0'
There is no trace experiment running.
`T1'
There is a trace experiment running.

File: gdb.info, Node: Interrupts, Next: Examples, Prev: Tracepoint Packets, Up: Remote Protocol
D.7 Interrupts
==============
When a program on the remote target is running, GDB may attempt to
interrupt it by sending a `Ctrl-C' or a `BREAK', control of which is
specified via GDB's `remotebreak' setting (*note set remotebreak::).
The precise meaning of `BREAK' is defined by the transport mechanism
and may, in fact, be undefined. GDB does not currently define a
`BREAK' mechanism for any of the network interfaces.
`Ctrl-C', on the other hand, is defined and implemented for all
transport mechanisms. It is represented by sending the single byte
`0x03' without any of the usual packet overhead described in the
Overview section (*note Overview::). When a `0x03' byte is transmitted
as part of a packet, it is considered to be packet data and does _not_
represent an interrupt. E.g., an `X' packet (*note X packet::), used
for binary downloads, may include an unescaped `0x03' as part of its
packet.
Stubs are not required to recognize these interrupt mechanisms and
the precise meaning associated with receipt of the interrupt is
implementation defined. If the stub is successful at interrupting the
running program, it is expected that it will send one of the Stop Reply
Packets (*note Stop Reply Packets::) to GDB as a result of successfully
stopping the program. Interrupts received while the program is stopped
will be discarded.

File: gdb.info, Node: Examples, Next: File-I/O remote protocol extension, Prev: Interrupts, Up: Remote Protocol
D.8 Examples
============
Example sequence of a target being re-started. Notice how the restart
does not get any direct output:
-> `R00'
<- `+'
_target restarts_
-> `?'
<- `+'
<- `T001:1234123412341234'
-> `+'
Example sequence of a target being stepped by a single instruction:
-> `G1445...'
<- `+'
-> `s'
<- `+'
_time passes_
<- `T001:1234123412341234'
-> `+'
-> `g'
<- `+'
<- `1455...'
-> `+'

File: gdb.info, Node: File-I/O remote protocol extension, Next: Memory map format, Prev: Examples, Up: Remote Protocol
D.9 File-I/O remote protocol extension
======================================
* Menu:
* File-I/O Overview::
* Protocol basics::
* The F request packet::
* The F reply packet::
* The Ctrl-C message::
* Console I/O::
* List of supported calls::
* Protocol specific representation of datatypes::
* Constants::
* File-I/O Examples::

File: gdb.info, Node: File-I/O Overview, Next: Protocol basics, Up: File-I/O remote protocol extension
D.9.1 File-I/O Overview
-----------------------
The "File I/O remote protocol extension" (short: File-I/O) allows the
target to use the host's file system and console I/O to perform various
system calls. System calls on the target system are translated into a
remote protocol packet to the host system, which then performs the
needed actions and returns a response packet to the target system.
This simulates file system operations even on targets that lack file
systems.
The protocol is defined to be independent of both the host and
target systems. It uses its own internal representation of datatypes
and values. Both GDB and the target's GDB stub are responsible for
translating the system-dependent value representations into the internal
protocol representations when data is transmitted.
The communication is synchronous. A system call is possible only
when GDB is waiting for a response from the `C', `c', `S' or `s'
packets. While GDB handles the request for a system call, the target
is stopped to allow deterministic access to the target's memory.
Therefore File-I/O is not interruptible by target signals. On the
other hand, it is possible to interrupt File-I/O by a user interrupt
(`Ctrl-C') within GDB.
The target's request to perform a host system call does not finish
the latest `C', `c', `S' or `s' action. That means, after finishing
the system call, the target returns to continuing the previous activity
(continue, step). No additional continue or step request from GDB is
required.
(gdb) continue
<- target requests 'system call X'
target is stopped, GDB executes system call
-> GDB returns result
... target continues, GDB returns to wait for the target
<- target hits breakpoint and sends a Txx packet
The protocol only supports I/O on the console and to regular files on
the host file system. Character or block special devices, pipes, named
pipes, sockets or any other communication method on the host system are
not supported by this protocol.

File: gdb.info, Node: Protocol basics, Next: The F request packet, Prev: File-I/O Overview, Up: File-I/O remote protocol extension
D.9.2 Protocol basics
---------------------
The File-I/O protocol uses the `F' packet as the request as well as
reply packet. Since a File-I/O system call can only occur when GDB is
waiting for a response from the continuing or stepping target, the
File-I/O request is a reply that GDB has to expect as a result of a
previous `C', `c', `S' or `s' packet. This `F' packet contains all
information needed to allow GDB to call the appropriate host system
call:
* A unique identifier for the requested system call.
* All parameters to the system call. Pointers are given as addresses
in the target memory address space. Pointers to strings are given
as pointer/length pair. Numerical values are given as they are.
Numerical control flags are given in a protocol specific
representation.
At this point, GDB has to perform the following actions.
* If the parameters include pointer values to data needed as input
to a system call, GDB requests this data from the target with a
standard `m' packet request. This additional communication has to
be expected by the target implementation and is handled as any
other `m' packet.
* GDB translates all value from protocol representation to host
representation as needed. Datatypes are coerced into the host
types.
* GDB calls the system call.
* It then coerces datatypes back to protocol representation.
* If the system call is expected to return data in buffer space
specified by pointer parameters to the call, the data is
transmitted to the target using a `M' or `X' packet. This packet
has to be expected by the target implementation and is handled as
any other `M' or `X' packet.
Eventually GDB replies with another `F' packet which contains all
necessary information for the target to continue. This at least
contains
* Return value.
* `errno', if has been changed by the system call.
* "Ctrl-C" flag.
After having done the needed type and value coercion, the target
continues the latest continue or step action.

File: gdb.info, Node: The F request packet, Next: The F reply packet, Prev: Protocol basics, Up: File-I/O remote protocol extension
D.9.3 The `F' request packet
----------------------------
The `F' request packet has the following format:
`FCALL-ID,PARAMETER...'
CALL-ID is the identifier to indicate the host system call to be
called. This is just the name of the function.
PARAMETER... are the parameters to the system call. Parameters
are hexadecimal integer values, either the actual values in case
of scalar datatypes, pointers to target buffer space in case of
compound datatypes and unspecified memory areas, or pointer/length
pairs in case of string parameters. These are appended to the
CALL-ID as a comma-delimited list. All values are transmitted in
ASCII string representation, pointer/length pairs separated by a
slash.

File: gdb.info, Node: The F reply packet, Next: The Ctrl-C message, Prev: The F request packet, Up: File-I/O remote protocol extension
D.9.4 The `F' reply packet
--------------------------
The `F' reply packet has the following format:
`FRETCODE,ERRNO,CTRL-C FLAG;CALL SPECIFIC ATTACHMENT'
RETCODE is the return code of the system call as hexadecimal value.
ERRNO is the `errno' set by the call, in protocol specific
representation. This parameter can be omitted if the call was
successful.
CTRL-C FLAG is only sent if the user requested a break. In this
case, ERRNO must be sent as well, even if the call was successful.
The CTRL-C FLAG itself consists of the character `C':
F0,0,C
or, if the call was interrupted before the host call has been
performed:
F-1,4,C
assuming 4 is the protocol specific representation of `EINTR'.

File: gdb.info, Node: The Ctrl-C message, Next: Console I/O, Prev: The F reply packet, Up: File-I/O remote protocol extension
D.9.5 The `Ctrl-C' message
--------------------------
If the `Ctrl-C' flag is set in the GDB reply packet (*note The F reply
packet::), the target should behave as if it had gotten a break
message. The meaning for the target is "system call interrupted by
`SIGINT'". Consequentially, the target should actually stop (as with a
break message) and return to GDB with a `T02' packet.
It's important for the target to know in which state the system call
was interrupted. There are two possible cases:
* The system call hasn't been performed on the host yet.
* The system call on the host has been finished.
These two states can be distinguished by the target by the value of
the returned `errno'. If it's the protocol representation of `EINTR',
the system call hasn't been performed. This is equivalent to the
`EINTR' handling on POSIX systems. In any other case, the target may
presume that the system call has been finished -- successfully or not
-- and should behave as if the break message arrived right after the
system call.
GDB must behave reliably. If the system call has not been called
yet, GDB may send the `F' reply immediately, setting `EINTR' as `errno'
in the packet. If the system call on the host has been finished before
the user requests a break, the full action must be finished by GDB.
This requires sending `M' or `X' packets as necessary. The `F' packet
may only be sent when either nothing has happened or the full action
has been completed.

File: gdb.info, Node: Console I/O, Next: List of supported calls, Prev: The Ctrl-C message, Up: File-I/O remote protocol extension
D.9.6 Console I/O
-----------------
By default and if not explicitely closed by the target system, the file
descriptors 0, 1 and 2 are connected to the GDB console. Output on the
GDB console is handled as any other file output operation (`write(1,
...)' or `write(2, ...)'). Console input is handled by GDB so that
after the target read request from file descriptor 0 all following
typing is buffered until either one of the following conditions is met:
* The user types `Ctrl-c'. The behaviour is as explained above, and
the `read' system call is treated as finished.
* The user presses <RET>. This is treated as end of input with a
trailing newline.
* The user types `Ctrl-d'. This is treated as end of input. No
trailing character (neither newline nor `Ctrl-D') is appended to
the input.
If the user has typed more characters than fit in the buffer given to
the `read' call, the trailing characters are buffered in GDB until
either another `read(0, ...)' is requested by the target, or debugging
is stopped at the user's request.

File: gdb.info, Node: List of supported calls, Next: Protocol specific representation of datatypes, Prev: Console I/O, Up: File-I/O remote protocol extension
D.9.7 List of supported calls
-----------------------------
* Menu:
* open::
* close::
* read::
* write::
* lseek::
* rename::
* unlink::
* stat/fstat::
* gettimeofday::
* isatty::
* system::

File: gdb.info, Node: open, Next: close, Up: List of supported calls
open
....
Synopsis:
int open(const char *pathname, int flags);
int open(const char *pathname, int flags, mode_t mode);
Request:
`Fopen,PATHPTR/LEN,FLAGS,MODE'
FLAGS is the bitwise `OR' of the following values:
`O_CREAT'
If the file does not exist it will be created. The host
rules apply as far as file ownership and time stamps are
concerned.
`O_EXCL'
When used with `O_CREAT', if the file already exists it is an
error and open() fails.
`O_TRUNC'
If the file already exists and the open mode allows writing
(`O_RDWR' or `O_WRONLY' is given) it will be truncated to
zero length.
`O_APPEND'
The file is opened in append mode.
`O_RDONLY'
The file is opened for reading only.
`O_WRONLY'
The file is opened for writing only.
`O_RDWR'
The file is opened for reading and writing.
Other bits are silently ignored.
MODE is the bitwise `OR' of the following values:
`S_IRUSR'
User has read permission.
`S_IWUSR'
User has write permission.
`S_IRGRP'
Group has read permission.
`S_IWGRP'
Group has write permission.
`S_IROTH'
Others have read permission.
`S_IWOTH'
Others have write permission.
Other bits are silently ignored.
Return value:
`open' returns the new file descriptor or -1 if an error occurred.
Errors:
`EEXIST'
PATHNAME already exists and `O_CREAT' and `O_EXCL' were used.
`EISDIR'
PATHNAME refers to a directory.
`EACCES'
The requested access is not allowed.
`ENAMETOOLONG'
PATHNAME was too long.
`ENOENT'
A directory component in PATHNAME does not exist.
`ENODEV'
PATHNAME refers to a device, pipe, named pipe or socket.
`EROFS'
PATHNAME refers to a file on a read-only filesystem and write
access was requested.
`EFAULT'
PATHNAME is an invalid pointer value.
`ENOSPC'
No space on device to create the file.
`EMFILE'
The process already has the maximum number of files open.
`ENFILE'
The limit on the total number of files open on the system has
been reached.
`EINTR'
The call was interrupted by the user.

File: gdb.info, Node: close, Next: read, Prev: open, Up: List of supported calls
close
.....
Synopsis:
int close(int fd);
Request:
`Fclose,FD'
Return value:
`close' returns zero on success, or -1 if an error occurred.
Errors:
`EBADF'
FD isn't a valid open file descriptor.
`EINTR'
The call was interrupted by the user.

File: gdb.info, Node: read, Next: write, Prev: close, Up: List of supported calls
read
....
Synopsis:
int read(int fd, void *buf, unsigned int count);
Request:
`Fread,FD,BUFPTR,COUNT'
Return value:
On success, the number of bytes read is returned. Zero indicates
end of file. If count is zero, read returns zero as well. On
error, -1 is returned.
Errors:
`EBADF'
FD is not a valid file descriptor or is not open for reading.
`EFAULT'
BUFPTR is an invalid pointer value.
`EINTR'
The call was interrupted by the user.

File: gdb.info, Node: write, Next: lseek, Prev: read, Up: List of supported calls
write
.....
Synopsis:
int write(int fd, const void *buf, unsigned int count);
Request:
`Fwrite,FD,BUFPTR,COUNT'
Return value:
On success, the number of bytes written are returned. Zero
indicates nothing was written. On error, -1 is returned.
Errors:
`EBADF'
FD is not a valid file descriptor or is not open for writing.
`EFAULT'
BUFPTR is an invalid pointer value.
`EFBIG'
An attempt was made to write a file that exceeds the host
specific maximum file size allowed.
`ENOSPC'
No space on device to write the data.
`EINTR'
The call was interrupted by the user.

File: gdb.info, Node: lseek, Next: rename, Prev: write, Up: List of supported calls
lseek
.....
Synopsis:
long lseek (int fd, long offset, int flag);
Request:
`Flseek,FD,OFFSET,FLAG'
FLAG is one of:
`SEEK_SET'
The offset is set to OFFSET bytes.
`SEEK_CUR'
The offset is set to its current location plus OFFSET bytes.
`SEEK_END'
The offset is set to the size of the file plus OFFSET bytes.
Return value:
On success, the resulting unsigned offset in bytes from the
beginning of the file is returned. Otherwise, a value of -1 is
returned.
Errors:
`EBADF'
FD is not a valid open file descriptor.
`ESPIPE'
FD is associated with the GDB console.
`EINVAL'
FLAG is not a proper value.
`EINTR'
The call was interrupted by the user.

File: gdb.info, Node: rename, Next: unlink, Prev: lseek, Up: List of supported calls
rename
......
Synopsis:
int rename(const char *oldpath, const char *newpath);
Request:
`Frename,OLDPATHPTR/LEN,NEWPATHPTR/LEN'
Return value:
On success, zero is returned. On error, -1 is returned.
Errors:
`EISDIR'
NEWPATH is an existing directory, but OLDPATH is not a
directory.
`EEXIST'
NEWPATH is a non-empty directory.
`EBUSY'
OLDPATH or NEWPATH is a directory that is in use by some
process.
`EINVAL'
An attempt was made to make a directory a subdirectory of
itself.
`ENOTDIR'
A component used as a directory in OLDPATH or new path is
not a directory. Or OLDPATH is a directory and NEWPATH
exists but is not a directory.
`EFAULT'
OLDPATHPTR or NEWPATHPTR are invalid pointer values.
`EACCES'
No access to the file or the path of the file.
`ENAMETOOLONG'
OLDPATH or NEWPATH was too long.
`ENOENT'
A directory component in OLDPATH or NEWPATH does not exist.
`EROFS'
The file is on a read-only filesystem.
`ENOSPC'
The device containing the file has no room for the new
directory entry.
`EINTR'
The call was interrupted by the user.

File: gdb.info, Node: unlink, Next: stat/fstat, Prev: rename, Up: List of supported calls
unlink
......
Synopsis:
int unlink(const char *pathname);
Request:
`Funlink,PATHNAMEPTR/LEN'
Return value:
On success, zero is returned. On error, -1 is returned.
Errors:
`EACCES'
No access to the file or the path of the file.
`EPERM'
The system does not allow unlinking of directories.
`EBUSY'
The file PATHNAME cannot be unlinked because it's being used
by another process.
`EFAULT'
PATHNAMEPTR is an invalid pointer value.
`ENAMETOOLONG'
PATHNAME was too long.
`ENOENT'
A directory component in PATHNAME does not exist.
`ENOTDIR'
A component of the path is not a directory.
`EROFS'
The file is on a read-only filesystem.
`EINTR'
The call was interrupted by the user.

File: gdb.info, Node: stat/fstat, Next: gettimeofday, Prev: unlink, Up: List of supported calls
stat/fstat
..........
Synopsis:
int stat(const char *pathname, struct stat *buf);
int fstat(int fd, struct stat *buf);
Request:
`Fstat,PATHNAMEPTR/LEN,BUFPTR'
`Ffstat,FD,BUFPTR'
Return value:
On success, zero is returned. On error, -1 is returned.
Errors:
`EBADF'
FD is not a valid open file.
`ENOENT'
A directory component in PATHNAME does not exist or the path
is an empty string.
`ENOTDIR'
A component of the path is not a directory.
`EFAULT'
PATHNAMEPTR is an invalid pointer value.
`EACCES'
No access to the file or the path of the file.
`ENAMETOOLONG'
PATHNAME was too long.
`EINTR'
The call was interrupted by the user.

File: gdb.info, Node: gettimeofday, Next: isatty, Prev: stat/fstat, Up: List of supported calls
gettimeofday
............
Synopsis:
int gettimeofday(struct timeval *tv, void *tz);
Request:
`Fgettimeofday,TVPTR,TZPTR'
Return value:
On success, 0 is returned, -1 otherwise.
Errors:
`EINVAL'
TZ is a non-NULL pointer.
`EFAULT'
TVPTR and/or TZPTR is an invalid pointer value.

File: gdb.info, Node: isatty, Next: system, Prev: gettimeofday, Up: List of supported calls
isatty
......
Synopsis:
int isatty(int fd);
Request:
`Fisatty,FD'
Return value:
Returns 1 if FD refers to the GDB console, 0 otherwise.
Errors:
`EINTR'
The call was interrupted by the user.
Note that the `isatty' call is treated as a special case: it returns
1 to the target if the file descriptor is attached to the GDB console,
0 otherwise. Implementing through system calls would require
implementing `ioctl' and would be more complex than needed.

File: gdb.info, Node: system, Prev: isatty, Up: List of supported calls
system
......
Synopsis:
int system(const char *command);
Request:
`Fsystem,COMMANDPTR/LEN'
Return value:
If LEN is zero, the return value indicates whether a shell is
available. A zero return value indicates a shell is not available.
For non-zero LEN, the value returned is -1 on error and the return
status of the command otherwise. Only the exit status of the
command is returned, which is extracted from the host's `system'
return value by calling `WEXITSTATUS(retval)'. In case `/bin/sh'
could not be executed, 127 is returned.
Errors:
`EINTR'
The call was interrupted by the user.
GDB takes over the full task of calling the necessary host calls to
perform the `system' call. The return value of `system' on the host is
simplified before it's returned to the target. Any termination signal
information from the child process is discarded, and the return value
consists entirely of the exit status of the called command.
Due to security concerns, the `system' call is by default refused by
GDB. The user has to allow this call explicitly with the `set remote
system-call-allowed 1' command.
`set remote system-call-allowed'
Control whether to allow the `system' calls in the File I/O
protocol for the remote target. The default is zero (disabled).
`show remote system-call-allowed'
Show whether the `system' calls are allowed in the File I/O
protocol.

File: gdb.info, Node: Protocol specific representation of datatypes, Next: Constants, Prev: List of supported calls, Up: File-I/O remote protocol extension
D.9.8 Protocol specific representation of datatypes
---------------------------------------------------
* Menu:
* Integral datatypes::
* Pointer values::
* Memory transfer::
* struct stat::
* struct timeval::

File: gdb.info, Node: Integral datatypes, Next: Pointer values, Up: Protocol specific representation of datatypes
Integral datatypes
..................
The integral datatypes used in the system calls are `int', `unsigned
int', `long', `unsigned long', `mode_t', and `time_t'.
`int', `unsigned int', `mode_t' and `time_t' are implemented as 32
bit values in this protocol.
`long' and `unsigned long' are implemented as 64 bit types.
*Note Limits::, for corresponding MIN and MAX values (similar to
those in `limits.h') to allow range checking on host and target.
`time_t' datatypes are defined as seconds since the Epoch.
All integral datatypes transferred as part of a memory read or write
of a structured datatype e.g. a `struct stat' have to be given in big
endian byte order.

File: gdb.info, Node: Pointer values, Next: Memory transfer, Prev: Integral datatypes, Up: Protocol specific representation of datatypes
Pointer values
..............
Pointers to target data are transmitted as they are. An exception is
made for pointers to buffers for which the length isn't transmitted as
part of the function call, namely strings. Strings are transmitted as
a pointer/length pair, both as hex values, e.g.
`1aaf/12'
which is a pointer to data of length 18 bytes at position 0x1aaf. The
length is defined as the full string length in bytes, including the
trailing null byte. For example, the string `"hello world"' at address
0x123456 is transmitted as
`123456/d'

File: gdb.info, Node: Memory transfer, Next: struct stat, Prev: Pointer values, Up: Protocol specific representation of datatypes
Memory transfer
...............
Structured data which is transferred using a memory read or write (for
example, a `struct stat') is expected to be in a protocol specific
format with all scalar multibyte datatypes being big endian.
Translation to this representation needs to be done both by the target
before the `F' packet is sent, and by GDB before it transfers memory to
the target. Transferred pointers to structured data should point to
the already-coerced data at any time.

File: gdb.info, Node: struct stat, Next: struct timeval, Prev: Memory transfer, Up: Protocol specific representation of datatypes
struct stat
...........
The buffer of type `struct stat' used by the target and GDB is defined
as follows:
struct stat {
unsigned int st_dev; /* device */
unsigned int st_ino; /* inode */
mode_t st_mode; /* protection */
unsigned int st_nlink; /* number of hard links */
unsigned int st_uid; /* user ID of owner */
unsigned int st_gid; /* group ID of owner */
unsigned int st_rdev; /* device type (if inode device) */
unsigned long st_size; /* total size, in bytes */
unsigned long st_blksize; /* blocksize for filesystem I/O */
unsigned long st_blocks; /* number of blocks allocated */
time_t st_atime; /* time of last access */
time_t st_mtime; /* time of last modification */
time_t st_ctime; /* time of last change */
};
The integral datatypes conform to the definitions given in the
appropriate section (see *Note Integral datatypes::, for details) so
this structure is of size 64 bytes.
The values of several fields have a restricted meaning and/or range
of values.
`st_dev'
A value of 0 represents a file, 1 the console.
`st_ino'
No valid meaning for the target. Transmitted unchanged.
`st_mode'
Valid mode bits are described in *Note Constants::. Any other
bits have currently no meaning for the target.
`st_uid'
`st_gid'
`st_rdev'
No valid meaning for the target. Transmitted unchanged.
`st_atime'
`st_mtime'
`st_ctime'
These values have a host and file system dependent accuracy.
Especially on Windows hosts, the file system may not support exact
timing values.
The target gets a `struct stat' of the above representation and is
responsible for coercing it to the target representation before
continuing.
Note that due to size differences between the host, target, and
protocol representations of `struct stat' members, these members could
eventually get truncated on the target.

File: gdb.info, Node: struct timeval, Prev: struct stat, Up: Protocol specific representation of datatypes
struct timeval
..............
The buffer of type `struct timeval' used by the File-I/O protocol is
defined as follows:
struct timeval {
time_t tv_sec; /* second */
long tv_usec; /* microsecond */
};
The integral datatypes conform to the definitions given in the
appropriate section (see *Note Integral datatypes::, for details) so
this structure is of size 8 bytes.

File: gdb.info, Node: Constants, Next: File-I/O Examples, Prev: Protocol specific representation of datatypes, Up: File-I/O remote protocol extension
D.9.9 Constants
---------------
The following values are used for the constants inside of the protocol.
GDB and target are responsible for translating these values before and
after the call as needed.
* Menu:
* Open flags::
* mode_t values::
* Errno values::
* Lseek flags::
* Limits::

File: gdb.info, Node: Open flags, Next: mode_t values, Up: Constants
Open flags
..........
All values are given in hexadecimal representation.
O_RDONLY 0x0
O_WRONLY 0x1
O_RDWR 0x2
O_APPEND 0x8
O_CREAT 0x200
O_TRUNC 0x400
O_EXCL 0x800

File: gdb.info, Node: mode_t values, Next: Errno values, Prev: Open flags, Up: Constants
mode_t values
.............
All values are given in octal representation.
S_IFREG 0100000
S_IFDIR 040000
S_IRUSR 0400
S_IWUSR 0200
S_IXUSR 0100
S_IRGRP 040
S_IWGRP 020
S_IXGRP 010
S_IROTH 04
S_IWOTH 02
S_IXOTH 01

File: gdb.info, Node: Errno values, Next: Lseek flags, Prev: mode_t values, Up: Constants
Errno values
............
All values are given in decimal representation.
EPERM 1
ENOENT 2
EINTR 4
EBADF 9
EACCES 13
EFAULT 14
EBUSY 16
EEXIST 17
ENODEV 19
ENOTDIR 20
EISDIR 21
EINVAL 22
ENFILE 23
EMFILE 24
EFBIG 27
ENOSPC 28
ESPIPE 29
EROFS 30
ENAMETOOLONG 91
EUNKNOWN 9999
`EUNKNOWN' is used as a fallback error value if a host system returns
any error value not in the list of supported error numbers.

File: gdb.info, Node: Lseek flags, Next: Limits, Prev: Errno values, Up: Constants
Lseek flags
...........
SEEK_SET 0
SEEK_CUR 1
SEEK_END 2

File: gdb.info, Node: Limits, Prev: Lseek flags, Up: Constants
Limits
......
All values are given in decimal representation.
INT_MIN -2147483648
INT_MAX 2147483647
UINT_MAX 4294967295
LONG_MIN -9223372036854775808
LONG_MAX 9223372036854775807
ULONG_MAX 18446744073709551615

File: gdb.info, Node: File-I/O Examples, Prev: Constants, Up: File-I/O remote protocol extension
D.9.10 File-I/O Examples
------------------------
Example sequence of a write call, file descriptor 3, buffer is at target
address 0x1234, 6 bytes should be written:
<- `Fwrite,3,1234,6'
_request memory read from target_
-> `m1234,6'
<- XXXXXX
_return "6 bytes written"_
-> `F6'
Example sequence of a read call, file descriptor 3, buffer is at
target address 0x1234, 6 bytes should be read:
<- `Fread,3,1234,6'
_request memory write to target_
-> `X1234,6:XXXXXX'
_return "6 bytes read"_
-> `F6'
Example sequence of a read call, call fails on the host due to
invalid file descriptor (`EBADF'):
<- `Fread,3,1234,6'
-> `F-1,9'
Example sequence of a read call, user presses `Ctrl-c' before
syscall on host is called:
<- `Fread,3,1234,6'
-> `F-1,4,C'
<- `T02'
Example sequence of a read call, user presses `Ctrl-c' after syscall
on host is called:
<- `Fread,3,1234,6'
-> `X1234,6:XXXXXX'
<- `T02'

File: gdb.info, Node: Memory map format, Prev: File-I/O remote protocol extension, Up: Remote Protocol
D.10 Memory map format
======================
To be able to write into flash memory, GDB needs to obtain a memory map
from the target. This section describes the format of the memory map.
The memory map is obtained using the `qXfer:memory-map:read' (*note
qXfer memory map read::) packet and is an XML document that lists
memory regions. The top-level structure of the document is shown below:
<?xml version="1.0"?>
<!DOCTYPE memory-map
PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
"http://sourceware.org/gdb/gdb-memory-map.dtd">
<memory-map>
region...
</memory-map>
Each region can be either:
* A region of RAM starting at ADDR and extending for LENGTH bytes
from there:
<memory type="ram" start="ADDR" length="LENGTH"/>
* A region of read-only memory:
<memory type="rom" start="ADDR" length="LENGTH"/>
* A region of flash memory, with erasure blocks BLOCKSIZE bytes in
length:
<memory type="flash" start="ADDR" length="LENGTH">
<property name="blocksize">BLOCKSIZE</property>
</memory>
Regions must not overlap. GDB assumes that areas of memory not
covered by the memory map are RAM, and uses the ordinary `M' and `X'
packets to write to addresses in such ranges.
The formal DTD for memory map format is given below:
<!-- ................................................... -->
<!-- Memory Map XML DTD ................................ -->
<!-- File: memory-map.dtd .............................. -->
<!-- .................................... .............. -->
<!-- memory-map.dtd -->
<!-- memory-map: Root element with versioning -->
<!ELEMENT memory-map (memory | property)>
<!ATTLIST memory-map version CDATA #FIXED "1.0.0">
<!ELEMENT memory (property)>
<!-- memory: Specifies a memory region,
and its type, or device. -->
<!ATTLIST memory type CDATA #REQUIRED
start CDATA #REQUIRED
length CDATA #REQUIRED
device CDATA #IMPLIED>
<!-- property: Generic attribute tag -->
<!ELEMENT property (#PCDATA | property)*>
<!ATTLIST property name CDATA #REQUIRED>

File: gdb.info, Node: Agent Expressions, Next: Copying, Prev: Remote Protocol, Up: Top
Appendix E The GDB Agent Expression Mechanism
*********************************************
In some applications, it is not feasable for the debugger to interrupt
the program's execution long enough for the developer to learn anything
helpful about its behavior. If the program's correctness depends on its
real-time behavior, delays introduced by a debugger might cause the
program to fail, even when the code itself is correct. It is useful to
be able to observe the program's behavior without interrupting it.
Using GDB's `trace' and `collect' commands, the user can specify
locations in the program, and arbitrary expressions to evaluate when
those locations are reached. Later, using the `tfind' command, she can
examine the values those expressions had when the program hit the trace
points. The expressions may also denote objects in memory --
structures or arrays, for example -- whose values GDB should record;
while visiting a particular tracepoint, the user may inspect those
objects as if they were in memory at that moment. However, because GDB
records these values without interacting with the user, it can do so
quickly and unobtrusively, hopefully not disturbing the program's
behavior.
When GDB is debugging a remote target, the GDB "agent" code running
on the target computes the values of the expressions itself. To avoid
having a full symbolic expression evaluator on the agent, GDB translates
expressions in the source language into a simpler bytecode language, and
then sends the bytecode to the agent; the agent then executes the
bytecode, and records the values for GDB to retrieve later.
The bytecode language is simple; there are forty-odd opcodes, the
bulk of which are the usual vocabulary of C operands (addition,
subtraction, shifts, and so on) and various sizes of literals and
memory reference operations. The bytecode interpreter operates
strictly on machine-level values -- various sizes of integers and
floating point numbers -- and requires no information about types or
symbols; thus, the interpreter's internal data structures are simple,
and each bytecode requires only a few native machine instructions to
implement it. The interpreter is small, and strict limits on the
memory and time required to evaluate an expression are easy to
determine, making it suitable for use by the debugging agent in
real-time applications.
* Menu:
* General Bytecode Design:: Overview of the interpreter.
* Bytecode Descriptions:: What each one does.
* Using Agent Expressions:: How agent expressions fit into the big picture.
* Varying Target Capabilities:: How to discover what the target can do.
* Tracing on Symmetrix:: Special info for implementation on EMC's
boxes.
* Rationale:: Why we did it this way.

File: gdb.info, Node: General Bytecode Design, Next: Bytecode Descriptions, Up: Agent Expressions
E.1 General Bytecode Design
===========================
The agent represents bytecode expressions as an array of bytes. Each
instruction is one byte long (thus the term "bytecode"). Some
instructions are followed by operand bytes; for example, the `goto'
instruction is followed by a destination for the jump.
The bytecode interpreter is a stack-based machine; most instructions
pop their operands off the stack, perform some operation, and push the
result back on the stack for the next instruction to consume. Each
element of the stack may contain either a integer or a floating point
value; these values are as many bits wide as the largest integer that
can be directly manipulated in the source language. Stack elements
carry no record of their type; bytecode could push a value as an
integer, then pop it as a floating point value. However, GDB will not
generate code which does this. In C, one might define the type of a
stack element as follows:
union agent_val {
LONGEST l;
DOUBLEST d;
};
where `LONGEST' and `DOUBLEST' are `typedef' names for the largest
integer and floating point types on the machine.
By the time the bytecode interpreter reaches the end of the
expression, the value of the expression should be the only value left
on the stack. For tracing applications, `trace' bytecodes in the
expression will have recorded the necessary data, and the value on the
stack may be discarded. For other applications, like conditional
breakpoints, the value may be useful.
Separate from the stack, the interpreter has two registers:
`pc'
The address of the next bytecode to execute.
`start'
The address of the start of the bytecode expression, necessary for
interpreting the `goto' and `if_goto' instructions.
Neither of these registers is directly visible to the bytecode
language itself, but they are useful for defining the meanings of the
bytecode operations.
There are no instructions to perform side effects on the running
program, or call the program's functions; we assume that these
expressions are only used for unobtrusive debugging, not for patching
the running code.
Most bytecode instructions do not distinguish between the various
sizes of values, and operate on full-width values; the upper bits of the
values are simply ignored, since they do not usually make a difference
to the value computed. The exceptions to this rule are:
memory reference instructions (`ref'N)
There are distinct instructions to fetch different word sizes from
memory. Once on the stack, however, the values are treated as
full-size integers. They may need to be sign-extended; the `ext'
instruction exists for this purpose.
the sign-extension instruction (`ext' N)
These clearly need to know which portion of their operand is to be
extended to occupy the full length of the word.
If the interpreter is unable to evaluate an expression completely for
some reason (a memory location is inaccessible, or a divisor is zero,
for example), we say that interpretation "terminates with an error".
This means that the problem is reported back to the interpreter's caller
in some helpful way. In general, code using agent expressions should
assume that they may attempt to divide by zero, fetch arbitrary memory
locations, and misbehave in other ways.
Even complicated C expressions compile to a few bytecode
instructions; for example, the expression `x + y * z' would typically
produce code like the following, assuming that `x' and `y' live in
registers, and `z' is a global variable holding a 32-bit `int':
reg 1
reg 2
const32 address of z
ref32
ext 32
mul
add
end
In detail, these mean:
`reg 1'
Push the value of register 1 (presumably holding `x') onto the
stack.
`reg 2'
Push the value of register 2 (holding `y').
`const32 address of z'
Push the address of `z' onto the stack.
`ref32'
Fetch a 32-bit word from the address at the top of the stack;
replace the address on the stack with the value. Thus, we replace
the address of `z' with `z''s value.
`ext 32'
Sign-extend the value on the top of the stack from 32 bits to full
length. This is necessary because `z' is a signed integer.
`mul'
Pop the top two numbers on the stack, multiply them, and push their
product. Now the top of the stack contains the value of the
expression `y * z'.
`add'
Pop the top two numbers, add them, and push the sum. Now the top
of the stack contains the value of `x + y * z'.
`end'
Stop executing; the value left on the stack top is the value to be
recorded.

File: gdb.info, Node: Bytecode Descriptions, Next: Using Agent Expressions, Prev: General Bytecode Design, Up: Agent Expressions
E.2 Bytecode Descriptions
=========================
Each bytecode description has the following form:
`add' (0x02): A B => A+B
Pop the top two stack items, A and B, as integers; push their sum,
as an integer.
In this example, `add' is the name of the bytecode, and `(0x02)' is
the one-byte value used to encode the bytecode, in hexidecimal. The
phrase "A B => A+B" shows the stack before and after the bytecode
executes. Beforehand, the stack must contain at least two values, A
and B; since the top of the stack is to the right, B is on the top of
the stack, and A is underneath it. After execution, the bytecode will
have popped A and B from the stack, and replaced them with a single
value, A+B. There may be other values on the stack below those shown,
but the bytecode affects only those shown.
Here is another example:
`const8' (0x22) N: => N
Push the 8-bit integer constant N on the stack, without sign
extension.
In this example, the bytecode `const8' takes an operand N directly
from the bytecode stream; the operand follows the `const8' bytecode
itself. We write any such operands immediately after the name of the
bytecode, before the colon, and describe the exact encoding of the
operand in the bytecode stream in the body of the bytecode description.
For the `const8' bytecode, there are no stack items given before the
=>; this simply means that the bytecode consumes no values from the
stack. If a bytecode consumes no values, or produces no values, the
list on either side of the => may be empty.
If a value is written as A, B, or N, then the bytecode treats it as
an integer. If a value is written is ADDR, then the bytecode treats it
as an address.
We do not fully describe the floating point operations here; although
this design can be extended in a clean way to handle floating point
values, they are not of immediate interest to the customer, so we avoid
describing them, to save time.
`float' (0x01): =>
Prefix for floating-point bytecodes. Not implemented yet.
`add' (0x02): A B => A+B
Pop two integers from the stack, and push their sum, as an integer.
`sub' (0x03): A B => A-B
Pop two integers from the stack, subtract the top value from the
next-to-top value, and push the difference.
`mul' (0x04): A B => A*B
Pop two integers from the stack, multiply them, and push the
product on the stack. Note that, when one multiplies two N-bit
numbers yielding another N-bit number, it is irrelevant whether the
numbers are signed or not; the results are the same.
`div_signed' (0x05): A B => A/B
Pop two signed integers from the stack; divide the next-to-top
value by the top value, and push the quotient. If the divisor is
zero, terminate with an error.
`div_unsigned' (0x06): A B => A/B
Pop two unsigned integers from the stack; divide the next-to-top
value by the top value, and push the quotient. If the divisor is
zero, terminate with an error.
`rem_signed' (0x07): A B => A MODULO B
Pop two signed integers from the stack; divide the next-to-top
value by the top value, and push the remainder. If the divisor is
zero, terminate with an error.
`rem_unsigned' (0x08): A B => A MODULO B
Pop two unsigned integers from the stack; divide the next-to-top
value by the top value, and push the remainder. If the divisor is
zero, terminate with an error.
`lsh' (0x09): A B => A<<B
Pop two integers from the stack; let A be the next-to-top value,
and B be the top value. Shift A left by B bits, and push the
result.
`rsh_signed' (0x0a): A B => `(signed)'A>>B
Pop two integers from the stack; let A be the next-to-top value,
and B be the top value. Shift A right by B bits, inserting copies
of the top bit at the high end, and push the result.
`rsh_unsigned' (0x0b): A B => A>>B
Pop two integers from the stack; let A be the next-to-top value,
and B be the top value. Shift A right by B bits, inserting zero
bits at the high end, and push the result.
`log_not' (0x0e): A => !A
Pop an integer from the stack; if it is zero, push the value one;
otherwise, push the value zero.
`bit_and' (0x0f): A B => A&B
Pop two integers from the stack, and push their bitwise `and'.
`bit_or' (0x10): A B => A|B
Pop two integers from the stack, and push their bitwise `or'.
`bit_xor' (0x11): A B => A^B
Pop two integers from the stack, and push their bitwise
exclusive-`or'.
`bit_not' (0x12): A => ~A
Pop an integer from the stack, and push its bitwise complement.
`equal' (0x13): A B => A=B
Pop two integers from the stack; if they are equal, push the value
one; otherwise, push the value zero.
`less_signed' (0x14): A B => A<B
Pop two signed integers from the stack; if the next-to-top value
is less than the top value, push the value one; otherwise, push
the value zero.
`less_unsigned' (0x15): A B => A<B
Pop two unsigned integers from the stack; if the next-to-top value
is less than the top value, push the value one; otherwise, push
the value zero.
`ext' (0x16) N: A => A, sign-extended from N bits
Pop an unsigned value from the stack; treating it as an N-bit
twos-complement value, extend it to full length. This means that
all bits to the left of bit N-1 (where the least significant bit
is bit 0) are set to the value of bit N-1. Note that N may be
larger than or equal to the width of the stack elements of the
bytecode engine; in this case, the bytecode should have no effect.
The number of source bits to preserve, N, is encoded as a single
byte unsigned integer following the `ext' bytecode.
`zero_ext' (0x2a) N: A => A, zero-extended from N bits
Pop an unsigned value from the stack; zero all but the bottom N
bits. This means that all bits to the left of bit N-1 (where the
least significant bit is bit 0) are set to the value of bit N-1.
The number of source bits to preserve, N, is encoded as a single
byte unsigned integer following the `zero_ext' bytecode.
`ref8' (0x17): ADDR => A
`ref16' (0x18): ADDR => A
`ref32' (0x19): ADDR => A
`ref64' (0x1a): ADDR => A
Pop an address ADDR from the stack. For bytecode `ref'N, fetch an
N-bit value from ADDR, using the natural target endianness. Push
the fetched value as an unsigned integer.
Note that ADDR may not be aligned in any particular way; the
`refN' bytecodes should operate correctly for any address.
If attempting to access memory at ADDR would cause a processor
exception of some sort, terminate with an error.
`ref_float' (0x1b): ADDR => D
`ref_double' (0x1c): ADDR => D
`ref_long_double' (0x1d): ADDR => D
`l_to_d' (0x1e): A => D
`d_to_l' (0x1f): D => A
Not implemented yet.
`dup' (0x28): A => A A
Push another copy of the stack's top element.
`swap' (0x2b): A B => B A
Exchange the top two items on the stack.
`pop' (0x29): A =>
Discard the top value on the stack.
`if_goto' (0x20) OFFSET: A =>
Pop an integer off the stack; if it is non-zero, branch to the
given offset in the bytecode string. Otherwise, continue to the
next instruction in the bytecode stream. In other words, if A is
non-zero, set the `pc' register to `start' + OFFSET. Thus, an
offset of zero denotes the beginning of the expression.
The OFFSET is stored as a sixteen-bit unsigned value, stored
immediately following the `if_goto' bytecode. It is always stored
most significant byte first, regardless of the target's normal
endianness. The offset is not guaranteed to fall at any particular
alignment within the bytecode stream; thus, on machines where
fetching a 16-bit on an unaligned address raises an exception, you
should fetch the offset one byte at a time.
`goto' (0x21) OFFSET: =>
Branch unconditionally to OFFSET; in other words, set the `pc'
register to `start' + OFFSET.
The offset is stored in the same way as for the `if_goto' bytecode.
`const8' (0x22) N: => N
`const16' (0x23) N: => N
`const32' (0x24) N: => N
`const64' (0x25) N: => N
Push the integer constant N on the stack, without sign extension.
To produce a small negative value, push a small twos-complement
value, and then sign-extend it using the `ext' bytecode.
The constant N is stored in the appropriate number of bytes
following the `const'B bytecode. The constant N is always stored
most significant byte first, regardless of the target's normal
endianness. The constant is not guaranteed to fall at any
particular alignment within the bytecode stream; thus, on machines
where fetching a 16-bit on an unaligned address raises an
exception, you should fetch N one byte at a time.
`reg' (0x26) N: => A
Push the value of register number N, without sign extension. The
registers are numbered following GDB's conventions.
The register number N is encoded as a 16-bit unsigned integer
immediately following the `reg' bytecode. It is always stored most
significant byte first, regardless of the target's normal
endianness. The register number is not guaranteed to fall at any
particular alignment within the bytecode stream; thus, on machines
where fetching a 16-bit on an unaligned address raises an
exception, you should fetch the register number one byte at a time.
`trace' (0x0c): ADDR SIZE =>
Record the contents of the SIZE bytes at ADDR in a trace buffer,
for later retrieval by GDB.
`trace_quick' (0x0d) SIZE: ADDR => ADDR
Record the contents of the SIZE bytes at ADDR in a trace buffer,
for later retrieval by GDB. SIZE is a single byte unsigned
integer following the `trace' opcode.
This bytecode is equivalent to the sequence `dup const8 SIZE
trace', but we provide it anyway to save space in bytecode strings.
`trace16' (0x30) SIZE: ADDR => ADDR
Identical to trace_quick, except that SIZE is a 16-bit big-endian
unsigned integer, not a single byte. This should probably have
been named `trace_quick16', for consistency.
`end' (0x27): =>
Stop executing bytecode; the result should be the top element of
the stack. If the purpose of the expression was to compute an
lvalue or a range of memory, then the next-to-top of the stack is
the lvalue's address, and the top of the stack is the lvalue's
size, in bytes.

File: gdb.info, Node: Using Agent Expressions, Next: Varying Target Capabilities, Prev: Bytecode Descriptions, Up: Agent Expressions
E.3 Using Agent Expressions
===========================
Here is a sketch of a full non-stop debugging cycle, showing how agent
expressions fit into the process.
* The user selects trace points in the program's code at which GDB
should collect data.
* The user specifies expressions to evaluate at each trace point.
These expressions may denote objects in memory, in which case
those objects' contents are recorded as the program runs, or
computed values, in which case the values themselves are recorded.
* GDB transmits the tracepoints and their associated expressions to
the GDB agent, running on the debugging target.
* The agent arranges to be notified when a trace point is hit. Note
that, on some systems, the target operating system is completely
responsible for collecting the data; see *Note Tracing on
Symmetrix::.
* When execution on the target reaches a trace point, the agent
evaluates the expressions associated with that trace point, and
records the resulting values and memory ranges.
* Later, when the user selects a given trace event and inspects the
objects and expression values recorded, GDB talks to the agent to
retrieve recorded data as necessary to meet the user's requests.
If the user asks to see an object whose contents have not been
recorded, GDB reports an error.

File: gdb.info, Node: Varying Target Capabilities, Next: Tracing on Symmetrix, Prev: Using Agent Expressions, Up: Agent Expressions
E.4 Varying Target Capabilities
===============================
Some targets don't support floating-point, and some would rather not
have to deal with `long long' operations. Also, different targets will
have different stack sizes, and different bytecode buffer lengths.
Thus, GDB needs a way to ask the target about itself. We haven't
worked out the details yet, but in general, GDB should be able to send
the target a packet asking it to describe itself. The reply should be a
packet whose length is explicit, so we can add new information to the
packet in future revisions of the agent, without confusing old versions
of GDB, and it should contain a version number. It should contain at
least the following information:
* whether floating point is supported
* whether `long long' is supported
* maximum acceptable size of bytecode stack
* maximum acceptable length of bytecode expressions
* which registers are actually available for collection
* whether the target supports disabled tracepoints

File: gdb.info, Node: Tracing on Symmetrix, Next: Rationale, Prev: Varying Target Capabilities, Up: Agent Expressions
E.5 Tracing on Symmetrix
========================
This section documents the API used by the GDB agent to collect data on
Symmetrix systems.
Cygnus originally implemented these tracing features to help EMC
Corporation debug their Symmetrix high-availability disk drives. The
Symmetrix application code already includes substantial tracing
facilities; the GDB agent for the Symmetrix system uses those facilities
for its own data collection, via the API described here.
-- Function: DTC_RESPONSE adbg_find_memory_in_frame (FRAME_DEF *FRAME,
char *ADDRESS, char **BUFFER, unsigned int *SIZE)
Search the trace frame FRAME for memory saved from ADDRESS. If
the memory is available, provide the address of the buffer holding
it; otherwise, provide the address of the next saved area.
* If the memory at ADDRESS was saved in FRAME, set `*BUFFER' to
point to the buffer in which that memory was saved, set
`*SIZE' to the number of bytes from ADDRESS that are saved at
`*BUFFER', and return `OK_TARGET_RESPONSE'. (Clearly, in
this case, the function will always set `*SIZE' to a value
greater than zero.)
* If FRAME does not record any memory at ADDRESS, set `*SIZE'
to the distance from ADDRESS to the start of the saved region
with the lowest address higher than ADDRESS. If there is no
memory saved from any higher address, set `*SIZE' to zero.
Return `NOT_FOUND_TARGET_RESPONSE'.
These two possibilities allow the caller to either retrieve the
data, or walk the address space to the next saved area.
This function allows the GDB agent to map the regions of memory
saved in a particular frame, and retrieve their contents efficiently.
This function also provides a clean interface between the GDB agent
and the Symmetrix tracing structures, making it easier to adapt the GDB
agent to future versions of the Symmetrix system, and vice versa. This
function searches all data saved in FRAME, whether the data is there at
the request of a bytecode expression, or because it falls in one of the
format's memory ranges, or because it was saved from the top of the
stack. EMC can arbitrarily change and enhance the tracing mechanism,
but as long as this function works properly, all collected memory is
visible to GDB.
The function itself is straightforward to implement. A single pass
over the trace frame's stack area, memory ranges, and expression blocks
can yield the address of the buffer (if the requested address was
saved), and also note the address of the next higher range of memory,
to be returned when the search fails.
As an example, suppose the trace frame `f' has saved sixteen bytes
from address `0x8000' in a buffer at `0x1000', and thirty-two bytes
from address `0xc000' in a buffer at `0x1010'. Here are some sample
calls, and the effect each would have:
`adbg_find_memory_in_frame (f, (char*) 0x8000, &buffer, &size)'
This would set `buffer' to `0x1000', set `size' to sixteen, and
return `OK_TARGET_RESPONSE', since `f' saves sixteen bytes from
`0x8000' at `0x1000'.
`adbg_find_memory_in_frame (f, (char *) 0x8004, &buffer, &size)'
This would set `buffer' to `0x1004', set `size' to twelve, and
return `OK_TARGET_RESPONSE', since `f' saves the twelve bytes from
`0x8004' starting four bytes into the buffer at `0x1000'. This
shows that request addresses may fall in the middle of saved
areas; the function should return the address and size of the
remainder of the buffer.
`adbg_find_memory_in_frame (f, (char *) 0x8100, &buffer, &size)'
This would set `size' to `0x3f00' and return
`NOT_FOUND_TARGET_RESPONSE', since there is no memory saved in `f'
from the address `0x8100', and the next memory available is at
`0x8100 + 0x3f00', or `0xc000'. This shows that request addresses
may fall outside of all saved memory ranges; the function should
indicate the next saved area, if any.
`adbg_find_memory_in_frame (f, (char *) 0x7000, &buffer, &size)'
This would set `size' to `0x1000' and return
`NOT_FOUND_TARGET_RESPONSE', since the next saved memory is at
`0x7000 + 0x1000', or `0x8000'.
`adbg_find_memory_in_frame (f, (char *) 0xf000, &buffer, &size)'
This would set `size' to zero, and return
`NOT_FOUND_TARGET_RESPONSE'. This shows how the function tells the
caller that no further memory ranges have been saved.
As another example, here is a function which will print out the
addresses of all memory saved in the trace frame `frame' on the
Symmetrix INLINES console:
void
print_frame_addresses (FRAME_DEF *frame)
{
char *addr;
char *buffer;
unsigned long size;
addr = 0;
for (;;)
{
/* Either find out how much memory we have here, or discover
where the next saved region is. */
if (adbg_find_memory_in_frame (frame, addr, &buffer, &size)
== OK_TARGET_RESPONSE)
printp ("saved %x to %x\n", addr, addr + size);
if (size == 0)
break;
addr += size;
}
}
Note that there is not necessarily any connection between the order
in which the data is saved in the trace frame, and the order in which
`adbg_find_memory_in_frame' will return those memory ranges. The code
above will always print the saved memory regions in order of increasing
address, while the underlying frame structure might store the data in a
random order.
[[This section should cover the rest of the Symmetrix functions the
stub relies upon, too.]]

File: gdb.info, Node: Rationale, Prev: Tracing on Symmetrix, Up: Agent Expressions
E.6 Rationale
=============
Some of the design decisions apparent above are arguable.
What about stack overflow/underflow?
GDB should be able to query the target to discover its stack size.
Given that information, GDB can determine at translation time
whether a given expression will overflow the stack. But this spec
isn't about what kinds of error-checking GDB ought to do.
Why are you doing everything in LONGEST?
Speed isn't important, but agent code size is; using LONGEST
brings in a bunch of support code to do things like division, etc.
So this is a serious concern.
First, note that you don't need different bytecodes for different
operand sizes. You can generate code without _knowing_ how big the
stack elements actually are on the target. If the target only
supports 32-bit ints, and you don't send any 64-bit bytecodes,
everything just works. The observation here is that the MIPS and
the Alpha have only fixed-size registers, and you can still get
C's semantics even though most instructions only operate on
full-sized words. You just need to make sure everything is
properly sign-extended at the right times. So there is no need
for 32- and 64-bit variants of the bytecodes. Just implement
everything using the largest size you support.
GDB should certainly check to see what sizes the target supports,
so the user can get an error earlier, rather than later. But this
information is not necessary for correctness.
Why don't you have `>' or `<=' operators?
I want to keep the interpreter small, and we don't need them. We
can combine the `less_' opcodes with `log_not', and swap the order
of the operands, yielding all four asymmetrical comparison
operators. For example, `(x <= y)' is `! (x > y)', which is `! (y
< x)'.
Why do you have `log_not'?
Why do you have `ext'?
Why do you have `zero_ext'?
These are all easily synthesized from other instructions, but I
expect them to be used frequently, and they're simple, so I
include them to keep bytecode strings short.
`log_not' is equivalent to `const8 0 equal'; it's used in half the
relational operators.
`ext N' is equivalent to `const8 S-N lsh const8 S-N rsh_signed',
where S is the size of the stack elements; it follows `refM' and
REG bytecodes when the value should be signed. See the next
bulleted item.
`zero_ext N' is equivalent to `constM MASK log_and'; it's used
whenever we push the value of a register, because we can't assume
the upper bits of the register aren't garbage.
Why not have sign-extending variants of the `ref' operators?
Because that would double the number of `ref' operators, and we
need the `ext' bytecode anyway for accessing bitfields.
Why not have constant-address variants of the `ref' operators?
Because that would double the number of `ref' operators again, and
`const32 ADDRESS ref32' is only one byte longer.
Why do the `refN' operators have to support unaligned fetches?
GDB will generate bytecode that fetches multi-byte values at
unaligned addresses whenever the executable's debugging
information tells it to. Furthermore, GDB does not know the value
the pointer will have when GDB generates the bytecode, so it
cannot determine whether a particular fetch will be aligned or not.
In particular, structure bitfields may be several bytes long, but
follow no alignment rules; members of packed structures are not
necessarily aligned either.
In general, there are many cases where unaligned references occur
in correct C code, either at the programmer's explicit request, or
at the compiler's discretion. Thus, it is simpler to make the GDB
agent bytecodes work correctly in all circumstances than to make
GDB guess in each case whether the compiler did the usual thing.
Why are there no side-effecting operators?
Because our current client doesn't want them? That's a cheap
answer. I think the real answer is that I'm afraid of
implementing function calls. We should re-visit this issue after
the present contract is delivered.
Why aren't the `goto' ops PC-relative?
The interpreter has the base address around anyway for PC bounds
checking, and it seemed simpler.
Why is there only one offset size for the `goto' ops?
Offsets are currently sixteen bits. I'm not happy with this
situation either:
Suppose we have multiple branch ops with different offset sizes.
As I generate code left-to-right, all my jumps are forward jumps
(there are no loops in expressions), so I never know the target
when I emit the jump opcode. Thus, I have to either always assume
the largest offset size, or do jump relaxation on the code after I
generate it, which seems like a big waste of time.
I can imagine a reasonable expression being longer than 256 bytes.
I can't imagine one being longer than 64k. Thus, we need 16-bit
offsets. This kind of reasoning is so bogus, but relaxation is
pathetic.
The other approach would be to generate code right-to-left. Then
I'd always know my offset size. That might be fun.
Where is the function call bytecode?
When we add side-effects, we should add this.
Why does the `reg' bytecode take a 16-bit register number?
Intel's IA-64 architecture has 128 general-purpose registers, and
128 floating-point registers, and I'm sure it has some random
control registers.
Why do we need `trace' and `trace_quick'?
Because GDB needs to record all the memory contents and registers
an expression touches. If the user wants to evaluate an expression
`x->y->z', the agent must record the values of `x' and `x->y' as
well as the value of `x->y->z'.
Don't the `trace' bytecodes make the interpreter less general?
They do mean that the interpreter contains special-purpose code,
but that doesn't mean the interpreter can only be used for that
purpose. If an expression doesn't use the `trace' bytecodes, they
don't get in its way.
Why doesn't `trace_quick' consume its arguments the way everything else does?
In general, you do want your operators to consume their arguments;
it's consistent, and generally reduces the amount of stack
rearrangement necessary. However, `trace_quick' is a kludge to
save space; it only exists so we needn't write `dup const8 SIZE
trace' before every memory reference. Therefore, it's okay for it
not to consume its arguments; it's meant for a specific context in
which we know exactly what it should do with the stack. If we're
going to have a kludge, it should be an effective kludge.
Why does `trace16' exist?
That opcode was added by the customer that contracted Cygnus for
the data tracing work. I personally think it is unnecessary;
objects that large will be quite rare, so it is okay to use `dup
const16 SIZE trace' in those cases.
Whatever we decide to do with `trace16', we should at least leave
opcode 0x30 reserved, to remain compatible with the customer who
added it.