#get/#set have 'volatile' semantics when compiled with GCC

Author: alexdowad

ext/atomic_reference.c

@@ -37,11 +37,17 @@ static VALUE ir_initialize(int argc, VALUE* argv, VALUE self) {
 }
 
 static VALUE ir_get(VALUE self) {
+#if HAVE_GCC_SYNC
+    __sync_synchronize();
+#endif
     return (VALUE) DATA_PTR(self);
 }
 
 static VALUE ir_set(VALUE self, VALUE new_value) {
     DATA_PTR(self) = (void *) new_value;
+#if HAVE_GCC_SYNC
+    __sync_synchronize();
+#endif
     return new_value;
 }
 

ext/extconf.rb

@@ -37,4 +37,11 @@ def compiler_is_gcc
   end
 end
 
+try_run(<<CODE,$CFLAGS) && ($defs << '-DHAVE_GCC_SYNC')
+int main() {
+  __sync_synchronize();
+  return 0;
+}
+CODE
+
 create_makefile(extension_name)