gnu: gcc@11: Patch libpthread on GNU/Hurd.

* gnu/packages/gcc.scm (gcc-11)[arguments]: Add 'patch-hurd-libpthread'
phase.
* gnu/packages/patches/gcc-11-libstdc++-hurd-libpthread.patch: New file.
* gnu/local.mk (dist_patch_DATA): Register it.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

gnu/local.mk

@@ -1181,6 +1181,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/gcc-9-strmov-store-file-names.patch	\
   %D%/packages/patches/gcc-12-strmov-store-file-names.patch	\
   %D%/packages/patches/gcc-10-cross-environment-variables.patch \
+  %D%/packages/patches/gcc-11-libstdc++-hurd-libpthread.patch   \
   %D%/packages/patches/gcc-12-cross-environment-variables.patch \
   %D%/packages/patches/gcc-10-tree-sra-union-handling.patch	\
   %D%/packages/patches/gcolor3-update-libportal-usage.patch	\

gnu/packages/gcc.scm

@@ -706,7 +706,18 @@ It also includes runtime support libraries for these languages.")
                                      "gcc-10-tree-sra-union-handling.patch"))
             (modules '((guix build utils)))
             (snippet gcc-canadian-cross-objdump-snippet)))
-
+   (arguments
+    (substitute-keyword-arguments (package-arguments gcc-8)
+      ((#:phases phases #~%standard-phases)
+       (if (target-hurd?)
+           #~(modify-phases #$phases
+               (add-after 'unpack 'patch-hurd-libpthread
+                 (lambda _
+                   (define patch
+                     #$(local-file
+                        (search-patch "gcc-11-libstdc++-hurd-libpthread.patch")))
+                   (invoke "patch" "--force" "-p1" "-i" patch))))
+           phases))))
    (properties
     `((compiler-cpu-architectures
        ("aarch64" ,@%gcc-11-aarch64-micro-architectures)

gnu/packages/patches/gcc-11-libstdc++-hurd-libpthread.patch

@@ -0,0 +1,62 @@
+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