[FFmpeg-devel] [PATCH] configure: link to libatomic when it's present

[Anton Khirnov]

C11 atomics in some configurations (e.g. 64bit operations on ppc64 with
GCC) require linking to libatomic.
---
Testing welcome, especially in configurations where
* libatomic is not present
* libatomic is actually needed
---
 configure | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/configure b/configure
index 1413122d87..1ff5dbee5b 100755
--- a/configure
+++ b/configure
@@ -6324,7 +6324,14 @@ check_headers asm/types.h
 # it seems there are versions of clang in some distros that try to use the
 # gcc headers, which explodes for stdatomic
 # so we also check that atomics actually work here
-check_builtin stdatomic stdatomic.h "atomic_int foo, bar = ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"
+#
+# some configurations also require linking to libatomic, so try
+# both with -latomic and without
+for LATOMIC in "-latomic" ""; do
+    check_builtin stdatomic stdatomic.h                                                 \
+        "atomic_int foo, bar = ATOMIC_VAR_INIT(-1); atomic_store(&foo, 0); foo += bar"  \
+        $LATOMIC && add_extralibs $LATOMIC && break
+done
 
 check_lib advapi32 "windows.h"            RegCloseKey          -ladvapi32
 check_lib bcrypt   "windows.h bcrypt.h"   BCryptGenRandom      -lbcrypt &&
-- 
2.33.0