Assert on async ccalls where they are not supported (emscripten-core#9124)

kripken · web-flow · commit b2d47565f5bf · 2019-08-01T14:19:40.000-07:00
This avoids confusing errors for users. Refs emscripten-core#9029.
diff --git a/src/preamble.js b/src/preamble.js
@@ -129,7 +129,12 @@ function ccall(ident, returnType, argTypes, args, opts) {
       });
     });
   }
+#else // EMTERPRETIFY_ASYNC
+#if ASSERTIONS
+  assert(!(opts && opts.async), 'async call is only supported with Emterpretify for now, see #9029');
 #endif
+#endif // EMTERPRETIFY_ASYNC
+
   ret = convertReturnValue(ret);
   if (stack !== 0) stackRestore(stack);
 #if EMTERPRETIFY_ASYNC
