[fuzzer] Print compilation error in wasm-compile

For debugging purposes, we print the validation error if the module
generated by WasmCompileFuzzer fails to validate.

Change-Id: I79d2827e489194d02150484ab5a196e979a302af
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3211574Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77295}

src/wasm/wasm-engine.cc

@@ -462,15 +462,22 @@ WasmEngine::~WasmEngine() {
 
 bool WasmEngine::SyncValidate(Isolate* isolate, const WasmFeatures& enabled,
                               const ModuleWireBytes& bytes) {
+  return SyncValidateResult(isolate, enabled, bytes).ok();
+}
+
+ModuleResult WasmEngine::SyncValidateResult(Isolate* isolate,
+                                            const WasmFeatures& enabled,
+                                            const ModuleWireBytes& bytes) {
   TRACE_EVENT0("v8.wasm", "wasm.SyncValidate");
   // TODO(titzer): remove dependency on the isolate.
-  if (bytes.start() == nullptr || bytes.length() == 0) return false;
-  ModuleResult result = DecodeWasmModule(
+  if (bytes.start() == nullptr || bytes.length() == 0) {
+    return ModuleResult(WasmError(0, "empty module wire bytes"));
+  }
+  return DecodeWasmModule(
       enabled, bytes.start(), bytes.end(), true, kWasmOrigin,
       isolate->counters(), isolate->metrics_recorder(),
       isolate->GetOrRegisterRecorderContextId(isolate->native_context()),
       DecodingMethod::kSync, allocator());
-  return result.ok();
 }
 
 MaybeHandle<AsmWasmData> WasmEngine::SyncCompileTranslatedAsmJs(

src/wasm/wasm-engine.h

@@ -45,8 +45,11 @@ class GdbServer;
 class AsyncCompileJob;
 class ErrorThrower;
 struct ModuleWireBytes;
+template <typename T>
+class Result;
 class StreamingDecoder;
 class WasmFeatures;
+using ModuleResult = Result<std::shared_ptr<WasmModule>>;
 
 class V8_EXPORT_PRIVATE CompilationResultResolver {
  public:
@@ -151,6 +154,10 @@ class V8_EXPORT_PRIVATE WasmEngine {
   // module.
   bool SyncValidate(Isolate* isolate, const WasmFeatures& enabled,
                     const ModuleWireBytes& bytes);
+  // Synchronously validates the given bytes that represent an encoded Wasm
+  // module.
+  ModuleResult SyncValidateResult(Isolate* isolate, const WasmFeatures& enabled,
+                                  const ModuleWireBytes& bytes);
 
   // Synchronously compiles the given bytes that represent a translated
   // asm.js module.

test/fuzzer/wasm-fuzzer-common.cc

@@ -627,11 +627,14 @@ void WasmExecutionFuzzer::FuzzWasmModule(base::Vector<const uint8_t> data,
     GenerateTestCase(i_isolate, wire_bytes, compiles);
   }
 
-  bool validates =
-      GetWasmEngine()->SyncValidate(i_isolate, enabled_features, wire_bytes);
-
-  CHECK_EQ(compiles, validates);
-  CHECK_IMPLIES(require_valid, validates);
+  ModuleResult result = GetWasmEngine()->SyncValidateResult(
+      i_isolate, enabled_features, wire_bytes);
+
+  CHECK_EQ(compiles, result.ok());
+  CHECK_WITH_MSG(
+      !require_valid || result.ok(),
+      ("Generated module should validate, but got: " + result.error().message())
+          .c_str());
 
   if (!compiles) return;