[wasm] Implement frame printing for debug

src/frames.cc

Index: src/frames.cc
diff --git a/src/frames.cc b/src/frames.cc
index 5920bfda8c4bb6484c1c06162db6e3f1ba4ccdc1..9f46d8e8b5cb0687daf4361fafdaf34c46516e23 100644
--- a/src/frames.cc
+++ b/src/frames.cc
@@ -1487,7 +1487,28 @@ void StackFrame::PrintIndex(StringStream* accumulator,
 
 void WasmFrame::Print(StringStream* accumulator, PrintMode mode,
                       int index) const {
-  accumulator->Add("wasm frame");
+  PrintIndex(accumulator, mode, index);
+  accumulator->Add("WASM [");
+  Script* script = this->script();
+  accumulator->PrintName(script->name());
+  int pc = static_cast<int>(this->pc() - LookupCode()->instruction_start());
+  Vector<const uint8_t> raw_func_name;
+  Object* instance_or_undef = this->wasm_instance();
+  if (instance_or_undef->IsUndefined(this->isolate())) {
+    raw_func_name = STATIC_CHAR_VECTOR("<undefined>");
+  } else {
+    raw_func_name = WasmInstanceObject::cast(instance_or_undef)
+                        ->get_compiled_module()
+                        ->GetRawFunctionName(this->function_index());
+  }
+  const int kMaxPrintedFunctionName = 64;
+  char func_name[kMaxPrintedFunctionName + 1];
+  int func_name_len = std::min(kMaxPrintedFunctionName, raw_func_name.length());
+  memcpy(func_name, raw_func_name.start(), func_name_len);
+  func_name[func_name_len] = '\0';
+  accumulator->Add("], function #%u ('%s'), pc=%p, pos=%d\n",

[titzer, 2016/11/18 10:38:21]

Does the accumulator pass the format string to printf underneath? If so, then
you should be able to do a %.*s and not have to make a copy of the raw_func_name
contents above.

[Clemens Hammacher, 2016/11/18 12:01:27]

No, unfortunately not. It does the formatting internally, which allows to also
handle Object* and Handle<Object>* properly.

+                   this->function_index(), func_name, pc, this->position());
+  if (mode != OVERVIEW) accumulator->Add("\n");
 }
 
 Code* WasmFrame::unchecked_code() const {