[llvm-dev] Minimal glibc version supported by LLVM build

[Rui Ueyama via llvm-dev]

+rafael who is the real author of the patch.

I think we should check if CPU_COUNT is available using CMake.

On Wed, Oct 4, 2017 at 11:17 AM, Philip Reames <listmail at philipreames.com>
wrote:

> + Rui, the patch author
>
> Do we know what the oldest glibc which works with this patch is?
>
> For context, the most recent REHL 5 ships with glibc 2.5.  REHL 6 ships
> with 2.12 and REHL ships with 2.17.  I have evidence that this breaks at
> least on Centos 6.4 which is derived from REHL 6.
>
> This appears to break on anything REHL 6 (or earlier) derived.  I think
> this patch needs to be reverted.  Thoughts?
>
> Philip
>
> On 10/04/2017 12:08 AM, Serguei Katkov via llvm-dev wrote:
>
> Hi All,
>
>
>
> The landed patch https://reviews.llvm.org/D38481 introduced the usage of
> CPU_COUNT defined in glibc sched.h header.
>
> I failed to find this symbol in sched.h of glibc version 2.5-24, so
> compilation just fails.
>
> /home/dolphin/merge-from-upstream-area/ws/pristine/lib/Support/Threading.cpp:
> In function ‘unsigned int llvm::hardware_concurrency()’:
>
> /home/dolphin/merge-from-upstream-area/ws/pristine/lib/Support/Threading.cpp:80:26:
> error: ‘CPU_COUNT’ was not declared in this scope
>
>      return CPU_COUNT(&Set);
>
>                           ^
>
>
>
> It is buildable with newest version of glibc.
>
> I tried to find a requirements for glibc version in LLVM documentation but
> failed.
>
> So I wonder whether there is such requirement or not.
>
> Could anyone point me to this documentation?
>
>
>
> I'm trying to understand whether patch is wrong which relies on
> availability of library but does not check the symbol itself or this
> version of glibc is not supported.
>
>
>
> Thank you,
>
> Serguei.
>
>
>
>
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>
>
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