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

[Emil Velikov]

On 13 April 2016 at 15:01, Nicolai Hähnle <nhaehnle at gmail.com> wrote:
> On 13.04.2016 08:25, Emil Velikov wrote:
>>
>> 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.
>
>
> Interesting. On my own build, `llvm-config --libs` produces the shared
> library, which is why I asked. OTOH, on the system LLVM, it produces the
> static libs even though the system installation also includes the shared
> libs. So yeah, this means it's unusable in its current form.
>
I know about the experimental option of LLVM producing multiple
(split) shared libraries, although your experience sounds quite new to
me.
Thanks that, had no idea it was possible.

-Emil