Add a compat stdatomic.h implementation based on GCC atomics

Adapted from the code by Rémi Denis-Courmont from VLC

This merges libav commit 4e928ef340ac20325f529d92fcbc51e768085358.

Signed-off-by: Wan-Teh Chang <wtc@google.com>
Reviewed-by: wm4 <nfxjfg@googlemail.com>
Signed-off-by: James Almer <jamrial@gmail.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/configure b/configure
index 6345fc2d0d..8cbe6f8c42 100755
--- a/configure
+++ b/configure
@@ -6381,6 +6381,12 @@ for thread in $THREADS_LIST; do
     fi
 done
 
+if disabled stdatomic_h; then
+    if enabled atomics_gcc; then
+        add_cppflags '-I\$(SRC_PATH)/compat/atomics/gcc'
+    fi
+fi
+
 enabled zlib && add_cppflags -DZLIB_CONST
 
 # conditional library dependencies, in linking order