git: af116659c071 - stable/15 - libc: Fix atomic_init for GCC atomic objects

The branch stable/15 has been updated by kfv:

URL: https://cgit.FreeBSD.org/src/commit/?id=af116659c071a284b036d4e8e232b107a7c3ecaa

commit af116659c071a284b036d4e8e232b107a7c3ecaa
Author:     Faraz Vahedi <kfv@FreeBSD.org>
AuthorDate: 2026-05-07 23:00:47 +0000
Commit:     Faraz Vahedi <kfv@FreeBSD.org>
CommitDate: 2026-10-31 10:03:31 +0000

    libc: Fix atomic_init for GCC atomic objects
    
    Add a dedicated `__GNUC_ATOMICS` path that initialises via
    `atomic_store_explicit(obj, value, memory_order_relaxed)`.
    
    This ensures the required initialisation semantics without
    assuming any particular object representation.
    
    Previously, `atomic_init` on GCC fell through to the legacy
    `__val` member path intended only for old struct-backed
    atomic objects. For current atomic objects, this caused the
    following compilation error:
    
    > error: request for member '__val' in something not a
      structure or union
    
    As a result, valid code such as `atomic_init(&x, 1)` failed
    to compile when using GCC.
    
    This fix restores compatibility with standard-conforming
    callers while other code paths remain unchanged.
    
    Signed-off-by: Faraz Vahedi <kfv@kfv.io>
    Reviewed by: imp
    Pull Request: https://github.com/freebsd/freebsd-src/pull/2185
    (cherry picked from commit 54ac231419cf09557d2f5826b1539e83db552410)
---
 sys/sys/stdatomic.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sys/sys/stdatomic.h b/sys/sys/stdatomic.h
index 3e4bdd505418..c0cbb7f785b5 100644
--- a/sys/sys/stdatomic.h
+++ b/sys/sys/stdatomic.h
@@ -96,6 +96,9 @@
 
 #if defined(__CLANG_ATOMICS)
 #define	atomic_init(obj, value)		__c11_atomic_init(obj, value)
+#elif defined(__GNUC_ATOMICS)
+#define	atomic_init(obj, value)		atomic_store_explicit(obj,	\
+	    value, __ATOMIC_RELAXED)
 #else
 #define	atomic_init(obj, value)		((void)((obj)->__val = (value)))
 #endif