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

[Philip Reames via llvm-dev]

+ 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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