whoops, missed a swift_once

Author: zhuowei

stdlib/public/runtime/CompatibilityOverride.h

@@ -39,7 +39,7 @@ namespace swift {
   Override_ ## name getOverride_ ## name();
 #include "CompatibilityOverride.def"
 
-
+#ifndef __wasm__
 /// Used to define an override point. The override point #defines the appropriate
 /// OVERRIDE macro from CompatibilityOverride.def to this macro, then includes
 /// the file to generate the override points. The original implementation of the
@@ -55,6 +55,20 @@ namespace swift {
       return Override(COMPATIBILITY_UNPAREN namedArgs, swift_ ## name ## Impl);   \
     return swift_ ## name ## Impl namedArgs; \
   }
+#else
+// WebAssembly: hack: change to swift_once_real
+#define COMPATIBILITY_OVERRIDE(name, ret, attrs, ccAttrs, namespace, typedArgs, namedArgs) \
+  attrs ccAttrs ret namespace swift_ ## name typedArgs {                          \
+    static Override_ ## name Override;                                            \
+    static swift_once_t Predicate;                                                \
+    swift_once_real(&Predicate, [](void *) {                                           \
+      Override = getOverride_ ## name();                                          \
+    }, nullptr);                                                                  \
+    if (Override != nullptr)                                                      \
+      return Override(COMPATIBILITY_UNPAREN namedArgs, swift_ ## name ## Impl);   \
+    return swift_ ## name ## Impl namedArgs; \
+  }
+#endif
 
 } /* end namespace swift */