[Mesa-dev] [PATCH] build: Fix LLVM shared library detection on systems with libLLVM.so.

[Emil Velikov]

On 13 April 2016 at 00:17, Nicolai Hähnle <nhaehnle at gmail.com> wrote:
> On 12.04.2016 12:58, Kenneth Graunke wrote:
>>
>> Arch Linux ships libLLVM.so.3.7.1 rather than libLLVM-3.7.1.so;
>> Mesa's configure script failed to find LLVM shared libraries in this
>> case.  I believe they build LLVM with CMake, but there is still only
>> one .so file.
>>
We had a similar patch [1] from the Archlinux maintainer and we sort
of rejected it. Why ?

Because it's a bug in the cmake build which (iirc) was fixed with LLVM
3.8. Shame that LLVM 3.7 series is busted with autoconf, thus one is
forced to use cmake ahead of autoconf deprecation (with 3.8).

Tom, I am a bit out of my waters here - can someone familiar with LLVM
flesh out a backport for the 3.7 (and 3.8?) series ?
Pretty please :-)

>> Signed-off-by: Kenneth Graunke <kenneth at whitecape.org>
>> ---
>>   configure.ac | 6 ++++++
>>   1 file changed, 6 insertions(+)
>>
>> This is mostly a strawman.  llvmpipe hasn't built on my system for
>> quite some time, and I finally got around to figuring out why.  I don't
>> know much about LLVM build issues (it seems complicated), so feel free
>> to throw this patch out and do it properly...
>
>
> I'm not that big on build system twiddling, so feel free to ignore me,
> but... why aren't we using $LLVM_CONFIG --libs here?
>
Because --libs produces
 - llvm 3.4 and earlier - the static libraries (modules) and their
dependencies (system libs)
 - llvm 3.5 and later only the static libraries (modules)

Neither of which is what we want in case of building against shared
LLVM. They are used when static linking LLVM.

Thanks
Emil

[1] https://patchwork.freedesktop.org/patch/60665/