Simon, thanks for the clarification. Does this mean that there's no
reliable way to get this information with the current V8 public API?
I went ahead and wrote a simple example illustrating the issue and tried
running it on different platforms. And the results were surprising.
Here's the sample code I wrote:
Isolate::CreateParams create_params;
create_params.array_buffer_allocator = &allocator_;
Isolate* isolate = Isolate::New(create_params);
Isolate::Scope isolate_scope(isolate);
HandleScope handle_scope(isolate);
Local<ObjectTemplate> globalTemplate = ObjectTemplate::New(isolate);
Local<Context> context = Context::New(isolate, nullptr, globalTemplate);
context->Enter();
Local<v8::Function> captureFunc = v8::Function::New(context, [](const
FunctionCallbackInfo<Value>& info) {
Isolate* isolate = info.GetIsolate();
Local<Context> context = isolate->GetCurrentContext();
Local<Object> exception =
Exception::Error(v8::String::NewFromUtf8(isolate, "",
NewStringType::kNormal, 0).ToLocalChecked()).As<Object>();
Local<Value> stackProperty = exception->Get(context,
v8::String::NewFromUtf8(isolate, "stack", NewStringType::kNormal,
5).ToLocalChecked()).ToLocalChecked();
v8::String::Utf8Value stackStr(isolate, stackProperty);
printf("%s\n\n", *stackStr);
Local<StackTrace> stack =
v8::StackTrace::CurrentStackTrace(isolate, 10,
v8::StackTrace::StackTraceOptions::kDetailed);
for (int i = 0; i < stack->GetFrameCount(); i++) {
Local<v8::StackFrame> frame = stack->GetFrame(isolate, i);
Local<v8::String> funcName = frame->GetFunctionName();
v8::String::Utf8Value str(isolate, funcName);
const char* name = *str;
printf("%s (%d:%d)\n", name, frame->GetLineNumber(),
frame->GetColumn());
}
}).ToLocalChecked();
assert(context->Global()->Set(context, v8::String::NewFromUtf8(isolate,
"captureTrace", NewStringType::kNormal, 12).ToLocalChecked(),
captureFunc).FromMaybe(false));
std::string src =
"(function test() {"
" const viewModel = new Object();"
" viewModel.onTap = () => { captureTrace(); };"
" viewModel.onTap.apply(viewModel, []);"
"})();";
Local<Script> script = Script::Compile(context,
v8::String::NewFromUtf8(isolate, src.c_str(), NewStringType::kNormal,
(int)src.length()).ToLocalChecked()).ToLocalChecked();
Local<Value> result;
assert(script->Run(context).ToLocal(&result));
On V8 8.0.0
(https://chromium.googlesource.com/v8/v8.git/+/50031fae736fac7b2b309369df492bfd0edd7553),
running in --jitless on an arm64 iOS device, I get the following output:
Error
at Object.onTap (<anonymous>:1:84)
at test (<anonymous>:1:122)
at <anonymous>:1:145
(null) (1:84)
test (1:122)
(null) (1:145)
and on V8 7.7.299.11
(https://chromium.googlesource.com/v8/v8.git/+/027689dbfcb2a9bbc8ceec4db2631c558e879633),
running on an arm64 Android device, I get the following output:
Error
at Object.viewModel.onTap (<anonymous>:1:84)
at test (<anonymous>:1:122)
at <anonymous>:1:145
viewModel.onTap (1:84)
test (1:122)
(null) (1:145)
Do you know what might explain the discrepancy between those two platforms?
On Tuesday, November 19, 2019 at 7:58:10 AM UTC+2, Simon Zünd wrote:
>
> This is a bug in our API implementation. Or better, there is a mismatch
> between API and what we do internally. "Method names" and "class names" are
> stored separately from function names. This can be seen here, when we
> collect all the information for a single frame:
> https://cs.chromium.org/chromium/src/v8/src/heap/factory.cc?rcl=e1eb815647f334a8cf970439343a8febfa9f6d11&l=3732
>
> There is really no reason why this information shouldn't be made available
> in the API. The only tricky thing is to come up with a better API, as some
> of the getters change meaning depending whether its a JS or WASM frame and
> I am not really happy with the current solution.
>
> On Mon, Nov 18, 2019 at 4:40 PM Darin Dimitrov <darin....@gmail.com
> <javascript:>> wrote:
>
>> I am embedding V8 and trying to capture the current javascript stacktrace
>> using the "v8::StackTrace::CurrentStackTrace":
>>
>> Isolate* isolate = info.GetIsolate();
>>
>> Local<StackTrace> stack = v8::StackTrace::CurrentStackTrace(isolate, 10,
>> v8::StackTrace::StackTraceOptions::kDetailed);
>>
>> *for* (*int* i = 0; i < stack->GetFrameCount(); i++) {
>>
>> Local<v8::StackFrame> frame = stack->GetFrame(isolate, i);
>>
>> Local<v8::String> funcName = frame->GetFunctionName();
>>
>> v8::String::Utf8Value str(isolate, funcName);
>>
>> *const* *char** name = *str;
>>
>> printf("%s (%d:%d)\n", name, frame->GetLineNumber(), frame->GetColumn
>> ());
>>
>> }
>>
>> I have placed this code inside a custom function that I have registered
>> to the global scope.
>>
>> Before calling my custom function, I tried logging the stack property of
>> an Error object (by using : console.log(new Error().stack)) and I obtained
>> the following output:
>>
>> Error
>> at bar (file:///app/bundle.js:266:29)
>> at test (file:///app/bundle.js:267:15)
>> at Observable.onTap (file:///app/bundle.js:268:11)
>> at Button.notify (file:///app/vendor.js:3620:32)
>> at Button._emit (file:///app/vendor.js:3640:18)
>> at TapHandlerImpl.tap (file:///app/vendor.js:15540:19)
>>
>> With the "v8::StackTrace::CurrentStackTrace" method I get:
>>
>> bar (266:29)
>> test (267:15)
>> (null) (268:11)
>> (null) (3620:32)
>> (null) (3640:18)
>> (null) (15540:19)
>>
>> I am getting empty function names from some frames, while all the other
>> information is present (script name, line, column numbers, ...).
>>
>> Do you know what might be the reason for getting empty function names?
>>
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>>
>
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