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LTP Style Guide
Welcome to the *LTP Project Coding Guideline* document! This document is
designed to guide committers and contributors in producing consistent, quality
deterministic testcases and port testcases from other sources to LTP so that
they can be easily maintained by project members and external contributors.
Please refer to the *Linux Kernel Coding Guidelines* unless stated otherwise
in this document.
* Initial version: Ngie Cooper <>
* Reformatted for asciidoc: Cyril Hrubis <>
Using libltp
Of course the manpages should be the primary source of information in
terms of how you should use libltp, but this section provides a quick
set of guidelines to hit the ground running with libltp.
When you can use libltp please observe the following guidelines:
1. Should I use tst_*() interface in forked processes?
No, only use libltp in non-forked processes and functions +perror(3)+ /
+exit(3)+ otherwise. Reason being:
* Calling +tst_resm()+ from multiple processes is messy.
* Calling cleanup can break test execution.
* Establishing a complicated scheme of tracking the testcase state
for teardown is undesirable.
2. Use SAFE_* macros
Use +SAFE_*+ macros (see +safe_macros.h+) instead of bare calls to libcalls and
syscalls. This will:
* Reduce number of lines wasted on repeated in multiple files with
error catching logic.
* Ensure that error catching is consistent and informative; all
+SAFE_*+ macros contain the line number of the failure as well as
the file where the failure occurred by design. So unless the
stack gets stomped on, you will be able to determine where
the failures occurred if and when they do occur with absolute
* Mute some unchecked return code warnings.
3. Don't call cleanup() from within setup()
Unless you need to clean up or reset system state that wouldn't otherwise be
handled by a proper release of all OS resources.
This includes (but is not limited to):
* Memory mapped pages.
* Mounted filesystems.
* File descriptors (if they're in temporary directories, etc).
* Temporary files / directories.
* Waiting for child processes.
* +/proc+ & +/sysfs+ tunable states.
You don't need to clean up the following:
* +malloc(3)+'ed memory.
* Read-only file descriptors in persistent paths (i.e. not
temporary directories).
Please be aware of some of the caveats surrounding forking,
exec'ing and descriptor inheritance, etc.
4. Call APIs that don't require freeing up resources on failure first
* +tst_require_root()+
* +tst_sig(...)+
* +malloc(3)+
* +tst_tmpdir()+
That way you can simplify your setup and avoid calling cleanup whenever
5. If the test needs to run as root
If the test need to run as root, check to make sure that you're root
*before doing any other setup* via +tst_require_root()+.
6. No custom reporting APIs
Don't roll your own reporting APIs unless you're porting testcases or are
concerned about portability.
7. Handle TBROK and TFAIL correctly
Use +TBROK+ when an unexpected failure unrelated to the goal of the testcase
occurred, and use +TFAIL+ when an unexpected failure related to the goal of
the testcase occurred.
8. Don't roll your own syscall numbers
Header +lapi/syscalls.h+ exists for this purpose and does a pretty
dang good job.
9. Keep errors as short and sweet as possible
For example:
if (fork() == -1)
tst_brkm(TBROK, cleanup, "fork failed");
/* or */
if (fork() == -1)
tst_brkm(TBROK, cleanup, "fork # 1 failed");
if (fork() == -1)
tst_brkm(TBROK, cleanup, "fork # 2 failed");
If you can't determine where the failure has occurred in a testcase based on
the entire content of the failure messages, then determining the cause of
failure may be impossible.
10. Reporting errno and the TEST() macro
Don't roll your own +errno+ / +strerror()+ printout when you use +tst_resm()+
calls. Use either +TERRNO+ or +TTERRNO+. Similarly, if a testcase passed and
it's obvious why it passed (for example a function call returns +0+ or
+TEST_RETURN == 0+).
/* Example without TEST(...) macro */
exp_errno = ENOENT;
if (fn() == -1) {
* Using TERRNO here is valid because the error case
* isn't static.
if (exp_errno == ENOENT)
"fn failed as expected");
* Using strerror(TEST_ERRNO) here is valid because
* the error case isn't static.
"fn failed unexpectedly; expected "
"%d - %s",
exp_errno, strerror(exp_errno));
} else
tst_resm(TBROK, "fn passed unexpectedly");
/* Example using TEST(...) macro */
if (TEST_RETURN == 0)
tst_resm(TPASS, "fn passed as expected");
tst_resm(TFAIL|TTERRNO, "fn failed");
The +TEST()+ macro is not thread-safe as it saves return value and errno into
global variable.
12. Use tst_brkm() when possible
tst_brkm(TBROK, cleanup, ...);
...instead of...
tst_resm(TBROK, ...);
As you see the +tst_brkm()+ no longer requires non +NULL+ cleanup_fn argument
in order to call +tst_exit()+.
13. Indentation
Use hard tabs for first-level indentation, and 4 spaces for every line longer
than 80 columns. Use a linebreak with string constants in format functions
like +*printf()+, the +tst_resm()+ APIs, etc.
if ((this_is_a_poorly_formed_really_long_variable = function_call()) == NULL &&
statement1() && i < j && l != 5) {
/* Use tabs here */
printf("The rain in Spain falls mainly in the plain.\nThe quick brown "
"fox jumped over the lazy yellow dog\n");
"Half would turn and fight. The other half would try to swim "
"across. But my uncle told me about a few that... they'd swim "
"halfway out, turn with the current, and ride it all the way out "
"to sea. Fisherman would find them a mile offshore, swimming.");
14. System headers
Don't use +linux/+ headers if at all possible. Usually they are replaced with
+sys/+ headers as things work their way into glibc. Furthermore, +linux/+
headers get shuffled around a lot more than their +sys/+ counterparts it
15. Signal handlers
Avoid doing tricky things in signal handlers. Calling most of the libc
functions from signal handler may lead to deadlocks or memory corruption. If
you really need to do anything more complicated that +should_run = 0;+ in your
signal handler consult +man 7 signal+ for async-signal-safe functions.
Porting Testcases
If one of the following is true...
1. You are porting a testcase directly to LTP which doesn't need to
be ported outside of Linux.
2. The beforementioned project or source is no longer contributing
changes to the testcases.
Then please fully port the testcase(s) to LTP. Otherwise, add robust porting
shims around the testcases using libltp APIs to reduce longterm maintenance
and leave the sources alone so it's easier to sync the testcases from the
upstream source.
New Testcases
1. Always use libltp for Linux centric tests. No ifs, ands, or buts
about it.
2. Sort headers, like:
* sys/types.h is usually (but not always) required by POSIX
* APIs.
#include <sys/types.h>
/* sys headers, alphabetical order. */
/* directory prefixed libc headers. */
/* non-directory prefixed libc headers. */
/* directory prefixed non-libc (third-party) headers. */
/* non-directory prefixed non-libc (third-party) headers. */
/* Sourcebase relative includes. */
/* e.g. */
#include <sys/types.h>
#include <sys/stat.h>
#include <netinet/icmp.h>
#include <stdio.h>
#include <dbus-1.0/dbus/dbus.h>
#include <archive.h>
#include "foo/bar.h"
#include "test.h"
Do not use obvious comments ("child process", "parse options", etc). This
leads to visual comment noise pollution.
4. Inline assignments
Don't do inline assignment, i.e.
int foo = 0;
Use separate statements:
int foo;
foo = 0;
The only exception to this is when you define global variables.
5. How to assert test is running as root?
Your testcase should be runnable as root and non-root. What does that mean? It
should fail gracefully as non-root if it has insufficient privileges, or use
+tst_require_root()+ if root access is absolutely required.
A lot of newer testcases don't honor this fact and it causes random
unnecessary errors when run as non-privileged users.
6. Do I need to create temporary directory?
Use +tst_tmpdir()+ if your testcase will:
* Create temporary files.
* Dump core.
* Etc. Otherwise, don't bother with the API.
If you created temporary directory with +tst_tmpdir()+ don't forget to call
+tst_rmdir()+ when the test is cleaning up. This is *NOT* done automatically.
7. Setting up signal handlers
Use +tst_sig()+ instead of bothering with sigaction / signal. This reduces
potential of leaving a mess around if your test doesn't exit cleanly (now,
there are some signals that can't be blocked, i.e. +SIGKILL+ and +SIGSTOP+,
but the rest can be caught).
8. Basic template
The following is a basic testcase template:
#include "test.h"
char *TCID = "testname";
int TST_TOTAL = /* ... */
static void setup(void)
/* ... */
/* ... */
static void cleanup(void)
/* ... */
int main(void)
/* ... */
setup(); /* Optional */
cleanup(); /* Optional */
tst_exit(); /* DON'T FORGET THIS -- this must be last! */
Fixing Legacy Testcases
Unless you interested in exercising self-masochism, do minimal changes
to testcases when fixing them so it's easier to track potential
breakage in testcases after a commit is made (mistakes happen and no
one is perfect). If it works after you fix it -- great -- move on.
It's more the job of the committers / maintainers to do things like
style commits.
It's better to focus on adding more content to LTP as a contributor
and fixing functional issues with existing tests than it is worrying
about whitespace, unnecessary pedanticness of function calls, etc.
As ugly as the style is in the surrounding code may be, stick to it.
Otherwise anyone reading the code will cringe at the chaos and
non-uniform `style', and it will be more difficult to fix later.
Fixing Open Posix Testsuite
The *Open Posix Testsuite* does not use libltp interface and moreover aims to
be usable on any *POSIX* compatible operating system.
So *NO* Linux, BSD specific syscalls there.
Contribution to the project
Since CVS is effectively dead for LTP proper, we ask that you submit
patches that are git friendly and patchable.
Guidelines for submitting patches are as follows:
1. Use +git commit -s+ . You know you want to ;) .. (you may need to
submit a correct signed-off-by line, e.g. use git config first).
2. Provide a short (<= 50 character) description of the commit.
3. Provide a little more terse (1-2 paragraph maximum, <= 72 character
lines) description of what the commit does.
4. Format the email with +git format-patch --attach+ command .
Example of a commit message:
Short description of my commit.
This is a much longer description of my commit. Blah blah blah blah
blah blah blah blah blah.
Signed-off-by: John Smith <dev@null>