build: make configure fail if both __atomic and __sync are not available

compat/atomics.h

@@ -24,7 +24,9 @@
 #if HAVE_ATOMIC_BUILTINS
 # define mp_memory_barrier()           __atomic_thread_fence(__ATOMIC_SEQ_CST)
 # define mp_atomic_add_and_fetch(a, b) __atomic_add_fetch(a, b,__ATOMIC_SEQ_CST)
-#else
+#elif HAVE_SYNC_BUILTINS
 # define mp_memory_barrier()           __sync_synchronize()
 # define mp_atomic_add_and_fetch(a, b) __sync_add_and_fetch(a, b)
+#else
+# error "this should have been a configuration error, report a bug please"
 #endif

old-configure

@@ -1343,6 +1343,23 @@ else
 fi
 echores "$_atomic"
 
+if test "$_atomic" = no ; then
+  echocheck "compiler support for __sync built-ins"
+  _sync=no
+  statement_check stdint.h 'int64_t test = 0; test = __sync_add_and_fetch(&test, 1)' && _sync=yes
+  if test "$_sync" = yes ; then
+    def_sync="#define HAVE_SYNC_BUILTINS 1"
+  else
+    def_sync="#define HAVE_SYNC_BUILTINS 0"
+  fi
+  echores "$_sync"
+else
+  def_sync="#define HAVE_SYNC_BUILTINS 0"
+fi
+
+if test "$_atomic" = no && test "$_sync" = no ; then
+  die "your compiler must support either __atomic or __aync bult-ins."
+fi
 
 if test "$_pthreads" = yes ; then
 
@@ -3537,6 +3554,7 @@ $def_avresample_has_set_channel_mapping
 $def_fast_64bit
 $def_pthreads
 $def_atomic
+$def_sync
 
 #define HAVE_INLINE_ASM 1
 

wscript

@@ -77,7 +77,7 @@ main_dependencies = [
         'desc': 'linker support for --nxcompat --no-seh --dynamicbase',
         'func': check_cc(linkflags=['-Wl,--nxcompat', '-Wl,--no-seh', '-Wl,--dynamicbase'])
     }, {
-        'name': 'ebx_available',
+        'name': 'ebx-available',
         'desc': 'ebx availability',
         'func': check_cc(fragment=load_fragment('ebx.c'))
     } , {
@@ -99,12 +99,26 @@ main_dependencies = [
         'req': True,
         'fmsg': 'Unable to find pthreads support.'
     }, {
-        'name': 'atomic_builtins',
+        'name': 'atomic-builtins',
         'desc': 'compiler support for __atomic built-ins',
         'func': check_libs(['atomic'],
             check_statement('stdint.h',
                 'int64_t test = 0;'
                 'test = __atomic_add_fetch(&test, 1, __ATOMIC_SEQ_CST)'))
+    }, {
+        'name': 'sync-builtins',
+        'desc': 'compiler support for __sync built-ins',
+        'func': check_statement('stdint.h',
+                    'int64_t test = 0;'
+                    'test = __sync_add_and_fetch(&test, 1)'),
+        'deps_neg': [ 'atomic-builtins' ],
+    }, {
+        'name': 'thread-synchronization-builtins',
+        'desc': 'compiler support for usable thread synchronization built-ins',
+        'func': check_true,
+        'deps_any': ['atomic-builtins', 'sync-builtins'],
+        'req': True,
+        'fmsg': 'your compiler must support either __atomic or __aync bult-ins',
     }, {
         'name': 'librt',
         'desc': 'linking with -lrt',