pydbattach - attach to running Python process

It probably should have been called pydbgattach or so but I didn't noticed until I went to bed so I keep this name now. :)

This works in several steps:

We are attaching to the running Python process and want to inject some C-code pyinjectcode.c.

Originally I planned to develop a small tool for this by myself based on ptrace. For Mac, I also found mach_inject which may have been useful.

However, to keep things simple for now, I just use GDB for this.

See the file pydbattach.sh which basically does this step.
pyinjectcode.c creates a new Python thread and runs a Python script. In our case, it runs pyinjectcode.py.
pyinjectcode.py starts a Pdb instance and attaches it to another already running Python process (just the first it founds for now). This is done via a more generic sys.settrace function which is implemented in pythreadhacks.py.
pythreadhacks.py heavily uses (_)ctypes to access the underlying CPython objects for the thread state. This way, it reimplements PyEval_SetTrace in a more general way.

dreiss/pydbattach