While the CMake support has gotten a lot less testing than
the Autotools-based build, the supported features should now
be equal. The output may differ slightly, for example,
liblzma.pc may have
Libs.private: -pthread -lpthread
with Autotools on GNU/Linux. CMake doesn't put any options
in Libs.private because on modern glibc the pthread functions
are in libc. The options options aren't required to link static
liblzma into an application.
Autotools-based build doesn't generate or install
lib/cmake/liblzma-*.cmake files. This means that on most
platforms one cannot rely on
find_package(liblzma 5.2.5 REQUIRED CONFIG)
or such finding those files.
It was weird to add CMAKE_THREAD_LIBS_INIT in CMAKE_REQUIRED_LIBRARIES
only if CLOCK_MONOTONIC is available. Alternative would be to remove
the thread libs from CMAKE_REQUIRED_LIBRARIES after the check for
pthread_condattr_setclock() but keeping the libs should be fine too.
Then it's ready in case more pthread functions were wanted some day.
In CMake, check_c_source_compiles() always links too. With
link-time optimization, unused functions may get omitted if
main() doesn't depend on them. Consider the following which
tries to check if somefunction() is available when <someheader.h>
has been included:
#include <someheader.h>
int foo(void) { return somefunction(); }
int main(void) { return 0; }
LTO may omit foo() completely because the program as a whole doesn't
need it and then the program will link even if the symbol somefunction
isn't available in libc or other library being linked in, and then
the test may pass when it shouldn't.
What happens if <someheader.h> doesn't declare somefunction()?
Shouldn't the test fail in the compilation phase already? It should
but many compilers don't follow the C99 and later standards that
prohibit implicit function declarations. Instead such compilers
assume that somefunction() exists, compilation succeeds (with a
warning), and then linker with LTO omits the call to somefunction().
Change the tests so that they are part of main(). If compiler accepts
implicitly declared functions, LTO cannot omit them because it has to
assume that they might have side effects and thus linking will fail.
On the other hand, if the functions/intrinsics being used are supported,
they might get optimized away but in that case it's fine because they
really are supported.
It is fine to use __attribute__((target(...))) for main(). At least
it works with GCC 4.9 to 14.1 on x86-64.
Reported-by: Sam James <sam@gentoo.org>
Now runtime detection of CLMUL support can pick between the CLMUL and
the generic assembly implementations. Whatever overhead this has for
builds that omit CLMUL completely isn't important because builds for
any non-ancient system is likely to include the CLMUL code too.
Handle the CRC tables in crcXX_fast.c files because now these files
are built even when assembly code is used.
If 32-bit x86 assembly is enabled then it will always be built even
if compiler flags were such that CLMUL would be allowed unconditionally.
That is, runtime detection will be used anyway. This keeps the build
rules simpler.
In LZ encoder, build and use lzma_lz_hash_table[256] if CLMUL CRC
is used without runtime detection. Previously this wasn't needed
because crc32_table.c included the lzma_crc32_table[][] in the build
unless encoder support had been disabled. Including an 8 KiB table
was silly when only 1 KiB is actually used. So now liblzma is 7 KiB
smaller if CLMUL is enabled without runtime detection.
It feels clearer this way, and when support for external SHA-256
is added, this will keep the order of the library detection the
same as in configure.ac (check for pthreads before libmd) although
it shouldn't matter in practice.
This simplifies things a little. Building liblzma with VS2013 probably
still worked but building the command line tools was not supported.
Microsoft ended support for VS2013 on 2024-04.
Make the available options and their behavior match
--enable-symbol-versions in configure.ac.
Don't enable symbol versions on Linux if not using glibc. Previously
the generic variant was selected on Microblaze or if using NVHPC
without checking that libc is glibc.
Leave the cache variable to "auto" or "yes" if that was specified
instead of setting it to the autodetected value by default. A downside
is that one cannot easily see which variant the autodetection code
has selected. The same applies to XZ_SANDBOX and XZ_THREADS though.
Also clarify that "yes" will fail if no threading support is found.
If no threading is wanted, it has to be disabled manually.
configure.ac doesn't behave this way at the moment. Instead it
assumes pthreads to be present if not targeting Windows. If pthreads
actually are missing, the build fails later.
The list was copied from configure.ac and should be kept in sync.
(Pretend that the deleted comment in CMakeLists.txt didn't exist.)
There is no need to add equivalent of --enable-werror as CMake >= 3.24
supports -DCMAKE_COMPILE_WARNING_AS_ERROR=ON.
This is for consistency with 4c81c9611f
where \040 has to be used because \0x20F gets interpret at three hex
digits. Octals escapes are never longer than three digits.
Now "crc32" is in the list too for completeness but it doesn't
actually have any effect. The description of the cache variable
says that "crc32 is always built" so it should be clear enough.
Update the description too.
It affects creation of not only the legacy lzma, unlzma, lzcat symlinks
but also lzgrep and other legacy names for the scripts. The last
LZMA Utils release was made in 2008 but these names are still used
in some places to handle .lzma files.
Also update the description to mention that this affects installation
of translated man pages too.
Prefixing the cache variables with the project name helps if
the package is used as a subproject in another package.
It also makes the package-specific options group more nicely
in ccmake and cmake-gui.
This way pthread options aren't passed to the linker when linking
against shared liblzma but they are still passed when linking against
static liblzma. (Also, one never needs the include path of the
threading library to use liblzma since liblzma's API headers
don't #include <pthread.h>. But <pthread.h> tends to be in the
default include path so here this change makes no difference.)
One cannot mix target_link_libraries() calls that use the scope
(PRIVATE, PUBLIC, or INTERFACE) keyword and calls that don't use it.
The calls without the keyword are like PUBLIC except perhaps when
they aren't, or something like that... It seems best to always
specify a scope keyword as the meanings of those three keywords
at least are clear.
Lasse Collin
Sam James