all: Don't use ATOMIC_VAR_INIT

C11 required to use ATOMIC_VAR_INIT to statically initialize
atomic objects with static storage duration. Yet this macro
was unsuitable for initializing structures [1] and was actually
unneeded for all known implementations (this includes our
compatibility fallback implementations which simply wrap the value
in parentheses: #define ATOMIC_VAR_INIT(value) (value)).
Therefore C17 deprecated the macro and C23 actually removed it [2].

Since commit 5ff0eb34d2 we default
to C17 if the compiler supports it; Clang warns about ATOMIC_VAR_INIT
in this mode. Given that no implementation ever needed this macro,
this commit stops using it to avoid this warning.

[1]: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2396.htm#dr_485
[2]: https://en.cppreference.com/w/c/atomic/ATOMIC_VAR_INIT

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

configure

@@ -6619,8 +6619,8 @@ check_headers asm/types.h
 # 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"  \
+    check_builtin stdatomic stdatomic.h                                \
+        "atomic_int foo, bar = -1; atomic_store(&foo, 0); foo += bar"  \
         $LATOMIC && eval stdatomic_extralibs="\$LATOMIC" && break
 done
 

fftools/ffmpeg.c

@@ -157,7 +157,7 @@ void term_exit(void)
 
 static volatile int received_sigterm = 0;
 static volatile int received_nb_signals = 0;
-static atomic_int transcode_init_done = ATOMIC_VAR_INIT(0);
+static atomic_int transcode_init_done = 0;
 static volatile int ffmpeg_exited = 0;
 static int64_t copy_ts_first_pts = AV_NOPTS_VALUE;
 

libavformat/allformats.c

@@ -576,8 +576,8 @@ extern const FFInputFormat  ff_vapoursynth_demuxer;
 #include "libavformat/muxer_list.c"
 #include "libavformat/demuxer_list.c"
 
-static atomic_uintptr_t indev_list_intptr  = ATOMIC_VAR_INIT(0);
-static atomic_uintptr_t outdev_list_intptr = ATOMIC_VAR_INIT(0);
+static atomic_uintptr_t indev_list_intptr  = 0;
+static atomic_uintptr_t outdev_list_intptr = 0;
 
 const AVOutputFormat *av_muxer_iterate(void **opaque)
 {

libavutil/cpu.c

@@ -49,8 +49,8 @@
 #include <unistd.h>
 #endif
 
-static atomic_int cpu_flags = ATOMIC_VAR_INIT(-1);
-static atomic_int cpu_count = ATOMIC_VAR_INIT(-1);
+static atomic_int cpu_flags = -1;
+static atomic_int cpu_count = -1;
 
 static int get_cpu_flags(void)
 {
@@ -208,7 +208,7 @@ int av_parse_cpu_caps(unsigned *flags, const char *s)
 
 int av_cpu_count(void)
 {
-    static atomic_int printed = ATOMIC_VAR_INIT(0);
+    static atomic_int printed = 0;
 
     int nb_cpus = 1;
     int count   = 0;

libavutil/mem.c

@@ -69,7 +69,7 @@ void  free(void *ptr);
  * dynamic libraries and remove -Wl,-Bsymbolic from the linker flags.
  * Note that this will cost performance. */
 
-static atomic_size_t max_alloc_size = ATOMIC_VAR_INIT(INT_MAX);
+static atomic_size_t max_alloc_size = INT_MAX;
 
 void av_max_alloc(size_t max){
     atomic_store_explicit(&max_alloc_size, max, memory_order_relaxed);