configure: check for stdatomic.h

Since this is a C11 feature, it requires -std=c11.

Not actually used for anything yet, that will be added in the following
commits.

1 files changed, 8 insertions, 1 deletions

diff --git a/configure b/configure
index f12fa6fa29..d5f58789a9 100755
--- a/configure
+++ b/configure
@@ -1504,6 +1504,7 @@ HEADERS_LIST="
     poll_h
     sndio_h
     soundcard_h
+    stdatomic_h
     sys_mman_h
     sys_param_h
     sys_resource_h
@@ -3669,7 +3670,7 @@ if test "$?" != 0; then
 fi
 
 add_cppflags -D_ISOC99_SOURCE
-check_cflags -std=c99
+check_cflags -std=c11 || check_cflags -std=c99
 check_cc -D_FILE_OFFSET_BITS=64 <<EOF && add_cppflags -D_FILE_OFFSET_BITS=64
 #include <stdlib.h>
 EOF
@@ -4512,6 +4513,12 @@ check_header VideoDecodeAcceleration/VDADecoder.h
 check_header windows.h
 check_header X11/extensions/XvMClib.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_header stdatomic.h &&
+    check_code cc "stdatomic.h" "atomic_int foo; atomic_store(&foo, 0)" || disable stdatomic_h
+
 check_lib2 "windows.h shellapi.h" CommandLineToArgvW -lshell32
 check_lib2 "windows.h wincrypt.h" CryptGenRandom -ladvapi32
 check_lib2 "windows.h psapi.h" GetProcessMemoryInfo -lpsapi