Debugging Step-into results in a stack-overflow like error

[jd-young]

Type: Bug

Typical debugging a C++ MFC program, step into a method then the debugger pauses for around two seconds and shows a 0xC0000005 access violation and the stack trace shows a load of mfc140d.dll, user32.dll, msvcp140d.dll and ntdll.dll calls with Unknown Source.

This happens seemingly randomly, in stepping into different functions on each run. Other debugging commands work as expected (step-over, step-out, etc), only step-into commands fail after a few step ins - like I say, seemingly at random and into different functions.

Extension version: 1.22.11
VS Code version: Code 1.96.2 (fabdb6a30b49f79a7aba0f2ad9df9b399473380f, 2024-12-19T10:22:47.216Z)
OS version: Windows_NT x64 10.0.22631
Modes:

System Info

Item	Value
CPUs	12th Gen Intel(R) Core(TM) i7-12700H (20 x 2688)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: enabled_on direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: disabled_off video_decode: enabled video_encode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: enabled webnn: disabled_off
Load (avg)	undefined
Memory (System)	31.69GB (15.76GB free)
Process Argv	--crash-reporter-id fc49156a-2f73-4514-b72b-578d62ca5db8
Screen Reader	no
VM	0%

A/B Experiments

vsliv368:30146709
vspor879:30202332
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vsaa593:30376534
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azure-dev_surveyone:30548225
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pythonnoceb:30805159
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pythontbext0:30879054
cppperfnew:31000557
dsvsc020:30976470
pythonait:31006305
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dwnewjupytercf:31046870
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pythonrstrctxt:31112756
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5fd0e150:31155592
dwcopilot:31170013
stablechunks:31184530
6074i472:31201624

[jd-young]

Okay, more information.

When the problem appeared, I got this in the debug console:

Debug Assertion Failed!

Program: C:\Users\jyoun\Projects\xxxx.exe
File: c:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Tools\MSVC\14.16.27023\include\deque
Line: 379

Expression: cannot seek deque iterator out of range

For information on how your program can cause an assertion
failure, see the Visual C++ documentation on asserts.

I don't use std::deque at all, but I do use a std::stack which turns out to use a deque. I also noticed that I had _fileStack._stack.top() in the Watch window and that when I stepped into a function, I saw 'The evaluation was aborted because of an unhandled exception occurred' (probably because the stack was empty).

When I removed the _stack entry from the Watch window, but program ran just fine, and I was able to step into functions just as normal.

So, there isn't a bug in either my software or Visual Code, however, it is far from obvious what was going wrong.

Maybe instead of classifiying this as a bug, we could change this to a request for improvement (or similar), to have Visual Code make it more obvious what the actual problem was. I'm not sure how to do that, and I am definitely alerted to this type of problem from now on, so probably not worth it for me, but my help some developers down the line.

[github-actions]

Thank you for reporting this issue. We’ll let you know if we need more information to investigate it. Additionally, if you're working with GDB/LLDB, please note that the code is open source at https://github.com/microsoft/MIEngine/wiki/Contributing-Code . Your contributions are always welcome and appreciated.