[Mesa-dev] [PATCH WIP 1/1] configure: include llvm systemlibs when using static llvm

[Emil Velikov]

On 27/10/14 21:03, Jan Vesely wrote:
> On Mon, 2014-10-27 at 20:22 +0000, Emil Velikov wrote:
>> On 27/10/14 18:05, Jan Vesely wrote:
>>> On Mon, 2014-10-27 at 02:24 +0000, Emil Velikov wrote:
>>>> On 26/10/14 19:36, Jan Vesely wrote:
>>>>> On Fri, 2014-10-24 at 23:54 +0000, Emil Velikov wrote:
>>>>>> On 24/10/14 17:03, Jan Vesely wrote:
>>>>>>> -Wl,--exclude-libs prevents automatic export of symbols
>>>>>>>
>>>>>>>
>>>>>>> CC: Kai Wasserbach <kai at dev.carbon-project.org>
>>>>>>> CC: Emil Velikov <emil.l.velikov at gmail.com>
>>>>>>> Signed-off-by: Jan Vesely <jan.vesely at rutgers.edu>
>>>>>>> ---
>>>>>>>
>>>>>>> Kai,
>>>>>>> can you try this patch with your setup, and check whether LLVM symbols are
>>>>>>> exported from mesa library? (and it's still working)
>>>>>>>
>>>>>>> Emil,
>>>>>>> would it help to have --exclude-libs ALL enabled globally?
>>>>>>>
>>>>>> Haven't really looked up on the documentation about it, yet there should
>>>>>> be no (unneeded) exported symbols thanks to the version scripts.
>>>>>> As such I'm not entirely sure what this patch (attempts to) resolve :(
>>>>>
>>>>> you are right. I don't know why I thought it was still a problem.
>>>>> In that case the attached patch should fix compiling with llvm static
>>>>> libs (#70410)
>>>>>
>>>> For future patches please add the full link in the commit message
>>>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=70410
>>>>
>>>> Afaics the bug mentioned has a slightly different patch, which brings
>>>> the question - do we need to append to the existing LLVM_LIBS, or can we
>>>> overwrite them ? Either way it would be nice if we can get a tested-by
>>>> or two :)
>>>
>>> Hi,
>>>
>>> I looked at this again. LLVM cmake links system-libs as either PUBLIC or
>>> INTERFACE [0].
>>> it means my patch is incorrect, and we should link against system-libs
>>> even if we use llvm-shared-libs.
>>> you can add my R-b to the patch by K. Sobiecky that is attached to the
>>> bug.[1]
>>>
>> Sigh... "cmake why you so PoS ?"
>>
>> On a more mature note:
>> I do not see why would we need it to link against those libraries for
>> shared linking. If their libs are broken (have unresolved symbols), and
>> we need this hack to get them working then maybe, but
>> ... looking at line 151 - # FIXME: Should this be really PUBLIC?
>> Answer: PRIVATE for shared libs, PUBLIC for static ones.
>>
>> Using PUBLIC causes all the users to recursively link against those
>> deps. Leading to over-linking and opening the door for serious issues.
> 
> looks like misdesign on llvm side. they use public to bring systemlibs
> to other llvm libs, while ignore private deps elsewhere (like libffi).
> I'd try to send a patch, but my last attempt to get Alexander's rtti
> patch in is stuck for 9 months...
> 
Yes, dealing with build systems is a job no-one wants to do, and I fear
most people underestimate it. Please let them know and be persistent
otherwise they might will end up abusing it too much :)

> anyway, since we only need those libs in static builds, do you want me
> to repost the patch with bug reference and Kai's tested by?
> 
There is no problem. I've picked it up, added the tags + cc'd
mesa-stable, as I would expect a few more people willing to use mesa
with static linked llvm.

Thanks
Emil

> jan
> 
>>
>>
>> -Emil
>>
>> P.S. Both their automake + cmake builds seems _quite_ bad.
>> autoconf/Readme has a nice documentation of it :)
>>
>>
>>> jan
>>>
>>>
>>> [0] lib/Support/CMakeLists.txt:150
>>> [1] https://bugs.freedesktop.org/attachment.cgi?id=91764
>>>>
>>>> Thanks
>>>> Emil
>>>>
>>>>> jan
>>>>>
>>>>>>
>>>>>> -Emil
>>>>>>
>>>>>>> jan
>>>>>>>
>>>>>>>  configure.ac | 10 +++++++++-
>>>>>>>  1 file changed, 9 insertions(+), 1 deletion(-)
>>>>>>>
>>>>>>> diff --git a/configure.ac b/configure.ac
>>>>>>> index 3c76deb..b4b4b13 100644
>>>>>>> --- a/configure.ac
>>>>>>> +++ b/configure.ac
>>>>>>> @@ -1981,7 +1981,15 @@ if test "x$MESA_LLVM" != x0; then
>>>>>>>             dnl already added all of these objects to LLVM_LIBS.
>>>>>>>          fi
>>>>>>>      else
>>>>>>> -        AC_MSG_WARN([Building mesa with staticly linked LLVM may cause compilation issues])
>>>>>>> +        AC_MSG_WARN([Building mesa with statically linked LLVM may cause compilation issues])
>>>>>>> +	dnl Don't export symbols automatically
>>>>>>> +	dnl TODO: Do we want to list llvm libs explicitly here?
>>>>>>> +	LLVM_LDFLAGS+=" -Wl,exclude-libs ALL"
>>>>>>> +	dnl We need to link to llvm system libs when using static libs
>>>>>>> +	dnl However, only llvm 3.5+ provides --system-libs
>>>>>>> +	if test $LLVM_VERSION_MAJOR -eq 3 -a $LLVM_VERSION_MINOR -ge 5; then
>>>>>>> +		LLVM_LIBS+=" `$LLVM_CONFIG --system-libs`"
>>>>>>> +	fi
>>>>>>>      fi
>>>>>>>  fi
>>>>>>>  
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>
>