[Buildroot] [PATCH 1/1] Fix build of lttng-libust

[Arnout Vandecappelle <arnout@mind.be>]

On 31-10-17 11:20, Norbert Lange wrote:
> Hello Thomas,
> 
> I dont know about the autobuilder (can I upload configs to test
> there?), this is an issue I encountered with a private buildroot
> config.
> I tried to reduce it as much as possible, and added the defconfig.
> 
> 2017-10-30 20:40 GMT+01:00 Thomas Petazzoni
> <thomas.petazzoni@free-electrons.com>:
>> Hello,
>>
>> On Mon, 30 Oct 2017 17:31:21 +0100, Norbert Lange wrote:
>>> The build of doc/examples/cmake-multiple-shared-libraries
>>> does fail as a dependend library is missing.
>>> This issue is not specific to builroot and should ideally
>>> be fixed upstream (Issue: https://bugs.lttng.org/issues/1132)
>>>
>>> The fix is done without any indepth knowledge of the CMake
>>> mechanisms, but seems to work correctly
>>>
>>> Signed-off-by: Norbert Lange <norbert.lange@andritz.com>
>>
>> Which specific build problem are you fixing? Is this a problem that has
>> been found by http://autobuild.buildroot.org? If that's the case, we
>> like to include a reference to such an autobuilder failure in the
>> commit log.

 It has not been found by the autobuilders, the only failure is
http://autobuild.buildroot.net/results/c86a82b2fd41316a7a451b20d9274d5c95f89baa
and that's due to CMake version.

 The build error is:

output/host/lib/gcc/x86_64-buildroot-linux-gnu/7.2.0/../../../../x86_64-buildroot-linux-gnu/bin/ld:
warning: liblttng-ust-tracepoint.so.0, needed by
output/build/lttng-libust-2.9.0/liblttng-ust/.libs/liblttng-ust.so, not found
(try using -rpath or -rpath-link)
output/build/lttng-libust-2.9.0/liblttng-ust/.libs/liblttng-ust.so: undefined
reference to `exit_tracepoint'
output/build/lttng-libust-2.9.0/liblttng-ust/.libs/liblttng-ust.so: undefined
reference to `__tracepoint_probe_unregister_queue_release'
output/build/lttng-libust-2.9.0/liblttng-ust/.libs/liblttng-ust.so: undefined
reference to `__tracepoint_probe_register_queue_release'
output/build/lttng-libust-2.9.0/liblttng-ust/.libs/liblttng-ust.so: undefined
reference to `__tracepoint_probe_prune_release_queue'
output/build/lttng-libust-2.9.0/liblttng-ust/.libs/liblttng-ust.so: undefined
reference to `init_tracepoint'
collect2: error: ld returned 1 exit status

 The weird thing is: liblttng-ust.so.0 does have the correct RPATH to find the
tracepoint library. And on all other builds I tried (and apparently including
all the autobuilders), it does find it. So I guess it's either binutils 2.29 or
GCC 7's LTO plugin that is acting up somehow...


 Since this is anyway just an example, wouldn't it be better to just disable the
documentation entirely? I.e. teach configure.ac to understand --disable-doc and
teach Makefile.am to not recurse into doc if docs are disabled?

 Regards,
 Arnout

-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
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