[wasm] Start function must not have a return value.

src/wasm/module-decoder.cc

Index: src/wasm/module-decoder.cc
diff --git a/src/wasm/module-decoder.cc b/src/wasm/module-decoder.cc
index 9aaf612134a6a97c90d287e8efeb3b1ebcbd2b72..d01a4f9a97ee45f96deb5d02b878cc4ac8025349 100644
--- a/src/wasm/module-decoder.cc
+++ b/src/wasm/module-decoder.cc
@@ -512,8 +512,10 @@ class ModuleDecoder : public Decoder {
       WasmFunction* func;
       const byte* pos = pc_;
       module->start_function_index = consume_func_index(module, &func);
-      if (func && func->sig->parameter_count() > 0) {
-        error(pos, "invalid start function: non-zero parameter count");
+      if (func &&
+          (func->sig->parameter_count() > 0 || func->sig->return_count() > 0)) {
+        error(pos,
+              "invalid start function: non-zero parameter or return count");
       }
       section_iter.advance();
     }