[PATCH] libstdc++: Ensure __gthread_self doesn't call undefined weak symbol [PR 95989]

[Jonathan Wakely]

On 12/11/20 17:34 +0000, Jonathan Wakely wrote:
>On 11/11/20 19:08 +0100, Jakub Jelinek via Libstdc++ wrote:
>>On Wed, Nov 11, 2020 at 05:24:42PM +0000, Jonathan Wakely wrote:
>>>--- a/libgcc/gthr-posix.h
>>>+++ b/libgcc/gthr-posix.h
>>>@@ -684,7 +684,14 @@ __gthread_equal (__gthread_t __t1, __gthread_t __t2)
>>> static inline __gthread_t
>>> __gthread_self (void)
>>> {
>>>+#if __GLIBC_PREREQ(2, 27)
>>
>>What if it is a non-glibc system where __GLIBC_PREREQ macro isn't defined?
>>I think you'd get then
>>error: missing binary operator before token "("
>>So I think you want
>>#if defined __GLIBC__ && defined __GLIBC_PREREQ
>>#if __GLIBC_PREREQ(2, 27)
>> return pthread_self ();
>>#else
>> return __gthrw_(pthread_self) ();
>>#else
>> return __gthrw_(pthread_self) ();
>>#endif
>>or similar.
>
>
>Here's a fixed version of the patch.
>
>I've moved the glibc-specific code in this_thread::get_id() into a new
>macro defined in config/os/gnu-linux/os_defines.h (where we already
>know we are dealing with glibc). That means we don't do the
>__GLIBC_PREREQ check directly in <thread>, it's hidden away in a
>target-specific header.
>
>Tested powerpc64le-linux (glibc 2.17 and 2.32), sparc-solaris2.11 and
>powerpc-aix.

I've committed this version which only fixes this_thread::get_id() in
libstdc++, and doesn't change __gthread_self in gthr-posix.h

Due to a recent change to replace other uses of __gthread_self with
calls to this_thread::get_id(), fixing it there fixes all uses in
libstdc++.

Tested x86_64-linux, powerpc-aix, sparc-solaris2.11, committed to
trunk.


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