Add Dart API method for getting current stack trace.

[DartBot]

This issue was originally filed by [email protected]

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This is needed to implement console.trace() which dumps current stack trace to inspector console.

[DartBot]

This comment was originally written by @mhausner

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When a breakpoint is hit, the breakpoint handler receives a handle to the stack trace. I will add a separate call to retrieve the current stack trace.

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Set owner to @mhausner.
Added Accepted label.

[DartBot]

This comment was originally written by @mhausner

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This functionality has been added. Closing the issue.

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Added Fixed label.

[DartBot]

This comment was originally written by [email protected]

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Looks like Dart_GetStackTrace works only from breakpoint handler.

To properly implement console.log we need a function that returns current stack trace when vm is not actually paused, like v8::StackTrace::CurrentStackTrace does.

Matthias, could you please fix the Dart_GetStackTrace function so that it works from arbitrary embedder's callback?

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Added Triaged label.

[DartBot]

This comment was originally written by @mhausner

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This feature request depends on the functionality to stop the VM from another thread, which is currently not implemented. At this point, we consider this a lower priority issue.

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Added this to the Later milestone.
Added Accepted label.

[DartBot]

This comment was originally written by [email protected]

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Why do we need to stop the VM from another thread to get current stack trace of an isolate in a native function?

Here is some context:
In dart:
class Console { void log(obj) native "Console_log_callback" }

In c++:
void Console_log_callback(Dart_NativeArguments args) {
  // (pseudo code)
  ConsoleMessage message = new ConsoleMessage(Dart_GetNativeArgument(args, 1));
  Dart_Handle stackTrace = Dart_GetStackTrace();
  Vector<Frame> frames;
  for (int i = 0; i < Length(stackTrace); ++i) {
    Dart_Handle activationFrame = ActivationFrameAt(stackTrace, i);
    frames.add(new Frame(ScriptUrl(activationFrame), LineNumber(activationFrame)));
  }
  message.setCallFrames(frames);
}

Here is a very rough implementation of what is needed https://chromiumcodereview.appspot.com/10808032/.
A link from print's output in console to the corresponding source code line is a very useful debugger feature. Would be nice to have it.

Sorry for not stating the problem clearly from the beginning.

[DartBot]

This comment was originally written by @mhausner

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You want a stack trace of an isolate that is "not actually paused" as you say above. I interpret this as "an isolate that is currently running code". That's why I said we need a way to stop the isolate to collect the stack trace.

If you are talking about an isolate that is not currently running (but not paused), then it's easier. But in that case, the stack is empty, isn't it?

I still don't know what exactly it is you would like to have...
 

[DartBot]

This comment was originally written by [email protected]

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Why do you expect the stack trace to be empty while executing a c++ calback? There should always be at least one dart frame which invoked the native function.

[DartBot]

This comment was originally written by [email protected]

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Issue #5851 has been merged into this issue.

[DartBot]

This comment was originally written by [email protected]

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Marked this as blocking #5851.

[DartBot]

This comment was originally written by @mhausner

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Added debugger label.

[iposva-google]

Removed Priority-Medium label.
Added Priority-Unassigned label.

[jacob314]

Removed this from the Later milestone.
Added this to the M7 milestone.
Removed Priority-Unassigned label.
Added Priority-Medium label.

[iposva-google]

Do I understand this request as equivalent to calling this helper method in Dart from a native method?

_getStackTrace() {
  try {
    throw "A";
  } catch (e, s) {
    return s.toString();
  }
}

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cc @a-siva.
Removed this from the M7 milestone.
Removed Priority-Medium label.
Added Priority-Unassigned label.

[iposva-google]

Siva, this request came from Dartium land. Is this still an issue?

[iposva-google]

Unmarked this as blocking #5851.

[iposva-google]

Removed debugger label.
Added NotPlanned label.

[jacob314]

This isn't a high priority Dartium issue at the moment. It would be nice if we had direct support like V8 does.
Currently we have to do the following which is a little ugly. captureParsedStackTrace is a method like the one iposva suggests.

    Dart_ExceptionPauseInfo previousPauseInfo = Dart_GetExceptionPauseInfo();
    if (previousPauseInfo != kNoPauseOnExceptions)
        Dart_SetExceptionPauseInfo(kNoPauseOnExceptions);
    Dart_Handle exception = 0;
    Dart_Handle parsedStackTrace = DartUtilities::invokeUtilsMethod("captureParsedStackTrace", 0, 0);

    if (previousPauseInfo != kNoPauseOnExceptions)
        Dart_SetExceptionPauseInfo(previousPauseInfo);

[blois]

I'm wondering if we can revisit the decision to not do this- the primary issue that I see is that relying on throwing exceptions causes issues with 'break on all exceptions'.

For example, Angular tests log the stack trace with all injections (https://github.com/angular/angular.dart/blob/9d190120f329bb766c7291dd96eb2f62b23f6f2f/lib/mock/test_injection.dart#L84), which throws hundreds of exceptions on start.

This makes it incredibly difficult to debug these tests.

In JS, this can be accomplished by using 'new Error().stack'

[a-siva]

This bug is for a request to provide a mechanism for getting a stack trace from the C/C++ Dart API. The example you have above with the Angular test case is more a request for a stacktrace from Dart code. I think you should redirect that to the library team.