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

[Anton Khirnov]

ffmpeg | branch: release/5.0 | Anton Khirnov <anton at khirnov.net> | Wed Jan 19 12:50:41 2022 +0100| [2bc8c87b2ec589ea7e9e97a9047733fc0fd7d643] | committer: Anton Khirnov

configure: link to libatomic when it's present

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

Fixes #9275

(cherry picked from commit 2f0a214a6202516b4dda2bb22b6b3ac20e465d6d)
Signed-off-by: Anton Khirnov <anton at khirnov.net>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=2bc8c87b2ec589ea7e9e97a9047733fc0fd7d643
---

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

diff --git a/configure b/configure
index 6b5ef6332e..7a62f0c248 100755
--- a/configure
+++ b/configure
@@ -3791,20 +3791,20 @@ 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"
@@ -6321,7 +6321,14 @@ 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 &&