[wasm-c-api] Fix signature deserialization

Func::type() was broken for functions created with Func::make().

Change-Id: I2867bcf00d9e5c1488165a804598c9ca8081ff25
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1655648
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Tamer Tas <tmrts@chromium.org>
Reviewed-by: Tamer Tas <tmrts@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62167}

src/wasm/c-api.cc

@@ -1618,12 +1618,12 @@ class SignatureHelper : public i::AllStatic {
     vec<ValType*> params = vec<ValType*>::make_uninitialized(param_arity);
 
     int i = 0;
-    for (; i < sig.length(); ++i) {
+    for (; i < result_arity; ++i) {
       results[i] = ValType::make(v8::wasm::v8_valtype_to_wasm(sig.get(i)));
     }
-    i++;
-    for (; i < param_arity; ++i) {
-      params[i] = ValType::make(v8::wasm::v8_valtype_to_wasm(sig.get(i)));
+    i++;  // Skip marker.
+    for (int p = 0; i < sig.length(); ++i, ++p) {
+      params[p] = ValType::make(v8::wasm::v8_valtype_to_wasm(sig.get(i)));
     }
     return FuncType::make(std::move(params), std::move(results));
   }

test/wasm-api-tests/OWNERS

+file://COMMON_OWNERS

test/wasm-api-tests/callbacks.cc

@@ -180,6 +180,8 @@ TEST_F(WasmCapiTest, GC) {
   i::Isolate* isolate =
       reinterpret_cast<::wasm::StoreImpl*>(store())->i_isolate();
   own<Func*> stage4 = Func::make(store(), cpp_sig(), Stage4_GC, isolate);
+  EXPECT_EQ(cpp_sig()->params().size(), stage4->type()->params().size());
+  EXPECT_EQ(cpp_sig()->results().size(), stage4->type()->results().size());
   Extern* imports[] = {stage2(), stage4.get()};
   Val args[] = {Val::i32(42)};
   Val results[1];