WinDbg Extensions for Python

This debugger extension provides visualizations for Python objects and stacktraces when debugging the CPython interpreter. It helps with live debugging and post-mortem analysis of dump files.

The goal of this project is to provide a similar debugging experience in WinDbg/CDB/NTSD as already exists in GDB.

Currently, the extension is tested against 32bit and 64bit builds of Python versions 2.7, 3.3, 3.4, 3.5, 3.6, 3.7 and 3.8.

Installation

• Build from source or download binaries from the Releases page
• Copy pyext.dll of the appropriate bitness into <WINDBG_ROOT><BITNESS>winext
• Ensure you have Microsoft Visual C++ 2017 Redistributable installed

Extension Commands

!pystack

Displays the Python callstack for the current thread.

Example usage:

0:000> !pystack
Thread 0:
    File "C:\Python36\lib\threading.py", line 1072, in _wait_for_tstate_lock
    File "C:\Python36\lib\threading.py", line 1056, in join
    File "scripts\win32debug.py", line 148, in _launch_and_wait
    File "scripts\win32debug.py", line 175, in dump_process
    File ".\fibonacci_test.py", line 18, in recursive_fib
    File ".\fibonacci_test.py", line 18, in recursive_fib
    File ".\fibonacci_test.py", line 18, in recursive_fib
    File ".\fibonacci_test.py", line 28, in <module>

Use ~*e!pystack to display the Python stack for all threads.

!pyobj

Displays the reference count, type, and value of a Python object, using similar formatting to Python's builtin repr() function.

Example usage:

0:000> !pyobj autoInterpreterState->tstate_head->frame->f_code
PyCodeObject at address: 000001fc`b6a87f60
RefCount: 2
Type: code
Repr: <code object, file "scripts\win32debug.py", line 120>

0:000> !pyobj autoInterpreterState->tstate_head->frame->f_globals
PyDictObject at address: 000001fc`b6ba6bd0
RefCount: 15
Type: dict
Repr: {
    '__name__': 'win32debug',
    '__doc__': 'Wrappers around various Win32 APIs debugging.',
# ...
}