[wasm] Differentiate unnamed and empty names

src/frames.cc

 // Copyright 2012 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.
 
 #include "src/frames.h"
 
 #include <sstream>
 
 #include "src/ast/ast.h"
 #include "src/ast/scopeinfo.h"
@@ skipping 1337 matching lines @@
   Object* func_index_obj = deopt_data->get(1);
   if (func_index_obj->IsUndefined()) return static_cast<uint32_t>(-1);
   if (func_index_obj->IsSmi()) return Smi::cast(func_index_obj)->value();
   DCHECK(func_index_obj->IsHeapNumber());
   uint32_t val = static_cast<uint32_t>(-1);
   func_index_obj->ToUint32(&val);
   DCHECK(val != static_cast<uint32_t>(-1));
   return val;
 }
 
-Object* WasmFrame::function_name() {
+String* WasmFrame::function_name() {
   Object* wasm_object = wasm_obj();
-  if (wasm_object->IsUndefined()) return wasm_object;
+  if (wasm_object->IsUndefined()) return nullptr;
   Handle<JSObject> wasm = handle(JSObject::cast(wasm_object));
-  return *wasm::GetWasmFunctionName(wasm, function_index());
+  MaybeHandle<String> name = wasm::GetWasmFunctionName(wasm, function_index());
+  return name.is_null() ? nullptr : *name.ToHandleChecked();

[Yang, 2016/05/18 13:38:48]

This whole method seems to have only one user. Why don't we simply compute the
name at the callsite from wasm_object() and function_index(). JavaScriptFrame
doesn't offer this functionality either.

[Clemens Hammacher, 2016/05/18 17:44:06]

Makes sense. Done.

 }
 
 namespace {
 
 
 void PrintFunctionSource(StringStream* accumulator, SharedFunctionInfo* shared,
                          Code* code) {
   if (FLAG_max_stack_trace_source_length != 0 && code != NULL) {
     std::ostringstream os;
     os << "--------- s o u r c e   c o d e ---------\n"
@@ skipping 419 matching lines @@
   for (StackFrameIterator it(isolate); !it.done(); it.Advance()) {
     StackFrame* frame = AllocateFrameCopy(it.frame(), zone);
     list.Add(frame, zone);
   }
   return list.ToVector();
 }
 
 
 }  // namespace internal
 }  // namespace v8