From f0065f207cf19cd960b33d961472c6d69514336f Mon Sep 17 00:00:00 2001
From: Samuel Thibault <samuel.thibault@gnu.org>
Date: Fri, 7 Oct 2022 22:45:06 +0200
Subject: [PATCH] libstdc++: Mark pieces of gnu-linux/os_support.h
 linux-specific

This is notably needed because in glibc 2.34, the move of pthread functions
into libc.so happened for Linux only, not GNU/Hurd.

The pthread_self() function can also always be used fine as it is on
GNU/Hurd.

libstdc++-v3/ChangeLog:

	* config/os/gnu-linux/os_defines.h [!__linux__]
	(_GLIBCXX_NATIVE_THREAD_ID, _GLIBCXX_GTHREAD_USE_WEAK): Do not define.

Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
---
 libstdc++-v3/config/os/gnu-linux/os_defines.h | 22 +++++++++++--------
 1 file changed, 13 insertions(+), 9 deletions(-)

diff --git a/libstdc++-v3/config/os/gnu-linux/os_defines.h b/libstdc++-v3/config/os/gnu-linux/os_defines.h
index 3064f8d908ac2..87317031fcd71 100644
--- a/libstdc++-v3/config/os/gnu-linux/os_defines.h
+++ b/libstdc++-v3/config/os/gnu-linux/os_defines.h
@@ -60,22 +60,26 @@
 # define _GLIBCXX_HAVE_FLOAT128_MATH 1
 #endif
 
-#if __GLIBC_PREREQ(2, 27)
+#ifdef __linux__
+// The following libpthread properties only apply to Linux, not GNU/Hurd.
+
+# if __GLIBC_PREREQ(2, 27)
 // Since glibc 2.27 pthread_self() is usable without linking to libpthread.
-# define _GLIBCXX_NATIVE_THREAD_ID pthread_self()
-#else
+#  define _GLIBCXX_NATIVE_THREAD_ID pthread_self()
+# else
 // Before then it was in libc.so.6 but not libc.a, and always returns 0,
 // which breaks the invariant this_thread::get_id() != thread::id{}.
 // So only use it if we know the libpthread version is available.
 // Otherwise use (__gthread_t)1 as the ID of the main (and only) thread.
-# define _GLIBCXX_NATIVE_THREAD_ID \
-  (__gthread_active_p() ? __gthread_self() : (__gthread_t)1)
-#endif
+#  define _GLIBCXX_NATIVE_THREAD_ID \
+   (__gthread_active_p() ? __gthread_self() : (__gthread_t)1)
+# endif
 
-#if __GLIBC_PREREQ(2, 34)
+# if __GLIBC_PREREQ(2, 34)
 // Since glibc 2.34 all pthreads functions are usable without linking to
 // libpthread.
-# define _GLIBCXX_GTHREAD_USE_WEAK 0
-#endif
+#  define _GLIBCXX_GTHREAD_USE_WEAK 0
+# endif
+#endif // __linux__
 
 #endif
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