commit | ebb3b9e23deb7df2b752bed8d75668b029495358 | [log] [tgz] |
---|---|---|
author | Peter Collingbourne <pcc@google.com> | Wed Dec 11 13:31:42 2019 -0800 |
committer | Peter Collingbourne <pcc@google.com> | Wed Dec 11 14:02:07 2019 -0800 |
tree | 053bb3ed39f50eb0b5c755b5a6b24899786054ef | |
parent | ab9b22a52761fc8de4becbfd036c2cd7d116e98a [diff] |
Stop building libexpat with -fexceptions. This flag is usually unnecessary when building C code. It is only useful when throwing exceptions across C stack frames, which isn't something that we generally support. Passing -fexceptions can create a dependency on the unwinder when building with HWASAN and possibly in other build configurations. With the change to move the unwinder into a shared library: https://android-review.googlesource.com/q/topic:%22libunwind-so%22 this would otherwise create an unnecessary dependency on the unwinder shared object from libexpat.so. We have been building expat with -fexceptions since the initial open source release. It doesn't seem to have been added for any Android-specific reason, but appears to have been inherited from the upstream build system, which originally started passing it in this commit from 2001: https://github.com/libexpat/libexpat/commit/d8263250ee5fe2eefc7cd94a05c5ee077912bc55 As far as I can tell, none of the code in the platform depends on expat being built with -fexceptions. Very little code in the platform builds with -fexceptions anyway, most notably a few libraries in external. One of these libraries, skia, uses expat, but does not use exceptions in the translation unit that uses expat. Chromium has the same dependency (skia -> expat) and isn't building expat with -fexceptions either. Bug: 144430859 Change-Id: I2188b30fb155e0e0241634fda6e45c6fe06c297a
This is Expat, a C library for parsing XML, started by James Clark in 1997. Expat is a stream-oriented XML parser. This means that you register handlers with the parser before starting the parse. These handlers are called when the parser discovers the associated structures in the document being parsed. A start tag is an example of the kind of structures for which you may register handlers.
Expat supports the following compilers:
Windows users should use the expat_win32
package, which includes both precompiled libraries and executables, and source code for developers.
Expat is free software. You may copy, distribute, and modify it under the terms of the License contained in the file COPYING
distributed with this package. This license is the same as the MIT/X Consortium license.
If you are building Expat from a check-out from the Git repository, you need to run a script that generates the configure script using the GNU autoconf and libtool tools. To do this, you need to have autoconf 2.58 or newer. Run the script like this:
./buildconf.sh
Once this has been done, follow the same instructions as for building from a source distribution.
To build Expat from a source distribution, you first run the configuration shell script in the top level distribution directory:
./configure
There are many options which you may provide to configure (which you can discover by running configure with the --help
option). But the one of most interest is the one that sets the installation directory. By default, the configure script will set things up to install libexpat into /usr/local/lib
, expat.h
into /usr/local/include
, and xmlwf
into /usr/local/bin
. If, for example, you'd prefer to install into /home/me/mystuff/lib
, /home/me/mystuff/include
, and /home/me/mystuff/bin
, you can tell configure
about that with:
./configure --prefix=/home/me/mystuff
Another interesting option is to enable 64-bit integer support for line and column numbers and the over-all byte index:
./configure CPPFLAGS=-DXML_LARGE_SIZE
However, such a modification would be a breaking change to the ABI and is therefore not recommended for general use — e.g. as part of a Linux distribution — but rather for builds with special requirements.
After running the configure script, the make
command will build things and make install
will install things into their proper location. Have a look at the Makefile
to learn about additional make
options. Note that you need to have write permission into the directories into which things will be installed.
If you are interested in building Expat to provide document information in UTF-16 encoding rather than the default UTF-8, follow these instructions (after having run make distclean
). Please note that we configure with --without-xmlwf
as xmlwf does not support this mode of compilation (yet):
Mass-patch Makefile.am
files to use libexpatw.la
for a library name:
find -name Makefile.am -exec sed -e 's,libexpat\.la,libexpatw.la,' -e 's,libexpat_la,libexpatw_la,' -i {} +
Run automake
to re-write Makefile.in
files:
automake
For UTF-16 output as unsigned short (and version/error strings as char), run:
./configure CPPFLAGS=-DXML_UNICODE --without-xmlwf
For UTF-16 output as wchar_t
(incl. version/error strings), run:
./configure CFLAGS="-g -O2 -fshort-wchar" CPPFLAGS=-DXML_UNICODE_WCHAR_T --without-xmlwf
Note: The latter requires libc compiled with -fshort-wchar
, as well.
Run make
(which excludes xmlwf).
Run make install
(again, excludes xmlwf).
Using DESTDIR
is supported. It works as follows:
make install DESTDIR=/path/to/image
overrides the in-makefile set DESTDIR
, because variable-setting priority is
Note: This only applies to the Expat library itself, building UTF-16 versions of xmlwf and the tests is currently not supported.
When using Expat with a project using autoconf for configuration, you can use the probing macro in conftools/expat.m4
to determine how to include Expat. See the comments at the top of that file for more information.
A reference manual is available in the file doc/reference.html
in this distribution.
The CMake build system is still experimental and will replace the primary build system based on GNU Autotools at some point when it is ready. For an idea of the available (non-advanced) options for building with CMake:
# rm -f CMakeCache.txt ; cmake -D_EXPAT_HELP=ON -LH . | grep -B1 ':.*=' | sed 's,^--$,,' // Choose the type of build, options are: None Debug Release RelWithDebInfo MinSizeRel ... CMAKE_BUILD_TYPE:STRING= // Install path prefix, prepended onto install directories. CMAKE_INSTALL_PREFIX:PATH=/usr/local // Path to a program. DOCBOOK_TO_MAN:FILEPATH=/usr/bin/docbook2x-man // build man page for xmlwf EXPAT_BUILD_DOCS:BOOL=ON // build the examples for expat library EXPAT_BUILD_EXAMPLES:BOOL=ON // build fuzzers for the expat library EXPAT_BUILD_FUZZERS:BOOL=OFF // build the tests for expat library EXPAT_BUILD_TESTS:BOOL=ON // build the xmlwf tool for expat library EXPAT_BUILD_TOOLS:BOOL=ON // Character type to use (char|ushort|wchar_t) [default=char] EXPAT_CHAR_TYPE:STRING=char // install expat files in cmake install target EXPAT_ENABLE_INSTALL:BOOL=ON // Use /MT flag (static CRT) when compiling in MSVC EXPAT_MSVC_STATIC_CRT:BOOL=OFF // build a shared expat library EXPAT_SHARED_LIBS:BOOL=ON // Treat all compiler warnings as errors EXPAT_WARNINGS_AS_ERRORS:BOOL=OFF // Make use of getrandom function (ON|OFF|AUTO) [default=AUTO] EXPAT_WITH_GETRANDOM:STRING=AUTO // utilize libbsd (for arc4random_buf) EXPAT_WITH_LIBBSD:BOOL=OFF // Make use of syscall SYS_getrandom (ON|OFF|AUTO) [default=AUTO] EXPAT_WITH_SYS_GETRANDOM:STRING=AUTO