Specific -var-create in core dump debugging is incredible slow

[borjamunozf]

Hello.

Summary
Debugging a C++ Core dump spent too much time waiting for the result of an specific -var-create (cutFrames).

The context is explained in this thread in C++ debugger extension.

• Details here - issue cpptools-12772

GDB command line does not suffer of this problem, overall debug took ~2 minutes.

Gathering debug info from MIENGINE

I was able to setup the debugger to debug OpenDebugAD7 process.

• Stepping through the code flow

MIEngine/src/MIDebugEngine/Engine.Impl/DebuggedProcess.cs

Line 2055 in 074837e

Results results = await MICommandFactory.VarCreate(n, thread.Id, (uint)level, 0, ResultClass.None);

• Command: 1106-var-create - * "cutFrames"
• After executing the CmdAsyncInternal I lost what's going on:

MIEngine/src/MICore/Debugger.cs

Lines 875 to 887 in 074837e

	public async Task<Results> CmdAsync(string command, ResultClass expectedResultClass)
	{
	await _commandLock.AquireShared();
	try
	{
	return await CmdAsyncInternal(command, expectedResultClass);
	}
	finally
	{
	_commandLock.ReleaseShared();
	}
	}

• Status of waitingOperations:
  

• Step into MITransport > StreamTransport > Task.Wait(token) (execute the task?) and takes minutes to reach the next line -> return task.Result;
  

  MIEngine/src/MICore/Transports/StreamTransport.cs

  Line 168 in 074837e

  task.Wait(token);

• After it returned, continuing stepping over I see this information on the overall status of the Debugger. There are two different exceptions, but I dont know if they're real or important at all for MICore.LocalTransport. _InvalidOperation*, process must exist before requested information can be determined.

• Nexts steps shows a ParseIssue? for it also shows the same for the other args (which seems to respond quickly)
  

Could you help me to identify what's going on? Any idea?
Thanks.

[borjamunozf]

Investigation ongoing:

• It could be that is not strictly a problem with MIEngine, but with GDB/MI.

Running this sequence of cmds:

gdb-multiarch --interpreter mi <binary> <coreDump>
-stack-select frame 4
- var-create  - * "cutFrames"

the faulty var-create - * "cutFrames" takes ~5-6 minutes!

I will open a bug/ticket in GDB/MI also, let's see if I can get any help :/