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Date: Wed, 11 Nov 2020 19:08:22 +0100
From: Jakub Jelinek <jakub@redhat.com>
To: Jonathan Wakely <jwakely@redhat.com>
Cc: libstdc++@gcc.gnu.org, gcc-patches@gcc.gnu.org,
 Florian Weimer <fweimer@redhat.com>
Subject: Re: [PATCH] libstdc++: Ensure __gthread_self doesn't call undefined
 weak symbol [PR 95989]
Message-ID: <20201111180822.GR3788@tucnak>
Reply-To: Jakub Jelinek <jakub@redhat.com>
References: <20201111172442.GA163354@redhat.com>
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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.

	Jakub