[wasm] Differentiate unnamed and empty names

src/wasm/wasm-module.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_WASM_MODULE_H_
 #define V8_WASM_MODULE_H_
 
 #include "src/wasm/wasm-opcodes.h"
 #include "src/wasm/wasm-result.h"
 
@@ skipping 177 matching lines @@
             static_cast<int>(length)};
   }
 
   // Get a string stored in the module bytes representing a function name.
   WasmName GetName(WasmFunction* function) const {
     return GetName(function->name_offset, function->name_length);
   }
 
   // Get a string stored in the module bytes representing a name.
   WasmName GetNameOrNull(uint32_t offset, uint32_t length) const {
-    if (length == 0) return {NULL, 0};  // no name.
+    if (offset == 0 && length == 0) return {NULL, 0};  // no name.
     CHECK(BoundsCheck(offset, offset + length));
     DCHECK_GE(static_cast<int>(length), 0);
     return {reinterpret_cast<const char*>(module_start + offset),
             static_cast<int>(length)};
   }
 
   // Get a string stored in the module bytes representing a function name.
   WasmName GetNameOrNull(WasmFunction* function) const {
     return GetNameOrNull(function->name_offset, function->name_length);
   }
@@ skipping 109 matching lines @@
 // For testing. Decode, verify, and run the last exported function in the
 // given encoded module.
 int32_t CompileAndRunWasmModule(Isolate* isolate, const byte* module_start,
                                 const byte* module_end, bool asm_js = false);
 
 // For testing. Decode, verify, and run the last exported function in the
 // given decoded module.
 int32_t CompileAndRunWasmModule(Isolate* isolate, WasmModule* module);
 
 // Extract a function name from the given wasm object.
-// Returns undefined if the function is unnamed or the function index is
-// invalid.
-Handle<Object> GetWasmFunctionName(Handle<JSObject> wasm, uint32_t func_index);
+// Returns a null handle if the function is unnamed or the name is not a valid
+// UTF-8 string.
+MaybeHandle<String> GetWasmFunctionName(Handle<JSObject> wasm,
+                                        uint32_t func_index);
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_MODULE_H_