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

[Anton Khirnov <anton@khirnov.net>]

C11 atomics in some configurations (e.g. 64bit operations on ppc64 with
GCC) require linking to libatomic.

Fixes #9275
---
 configure | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/configure b/configure
index 1413122d87..3059c154df 100755
--- a/configure
+++ b/configure
@@ -3794,20 +3794,20 @@ cws2fws_extralibs="zlib_extralibs"
 
 # libraries, in any order
 avcodec_deps="avutil"
-avcodec_suggest="libm"
+avcodec_suggest="libm stdatomic"
 avdevice_deps="avformat avcodec avutil"
-avdevice_suggest="libm"
+avdevice_suggest="libm stdatomic"
 avfilter_deps="avutil"
-avfilter_suggest="libm"
+avfilter_suggest="libm stdatomic"
 avformat_deps="avcodec avutil"
-avformat_suggest="libm network zlib"
-avutil_suggest="clock_gettime ffnvcodec libm libdrm libmfx opencl user32 vaapi vulkan videotoolbox corefoundation corevideo coremedia bcrypt"
+avformat_suggest="libm network zlib stdatomic"
+avutil_suggest="clock_gettime ffnvcodec libm libdrm libmfx opencl user32 vaapi vulkan videotoolbox corefoundation corevideo coremedia bcrypt stdatomic"
 postproc_deps="avutil gpl"
-postproc_suggest="libm"
+postproc_suggest="libm stdatomic"
 swresample_deps="avutil"
-swresample_suggest="libm libsoxr"
+swresample_suggest="libm libsoxr stdatomic"
 swscale_deps="avutil"
-swscale_suggest="libm"
+swscale_suggest="libm stdatomic"
 
 avcodec_extralibs="pthreads_extralibs iconv_extralibs dxva2_extralibs"
 avfilter_extralibs="pthreads_extralibs"
@@ -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 && eval stdatomic_extralibs="\$LATOMIC" && break
+done
 
 check_lib advapi32 "windows.h"            RegCloseKey          -ladvapi32
 check_lib bcrypt   "windows.h bcrypt.h"   BCryptGenRandom      -lbcrypt &&
-- 
2.33.0

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