How to make pdb recognize that the source has changed between runs?

Question

From what I can tell, pdb does not recognize when the source code has changed between "runs". That is, if I'm debugging, notice a bug, fix that bug, and rerun the program in pdb (i.e. without exiting pdb), pdb will not recompile the code. I'll still be debugging the old version of the code, even if pdb lists the new source code.

So, does pdb not update the compiled code as the source changes? If not, is there a way to make it do so? I'd like to be able to stay in a single pdb session in order to keep my breakpoints and such.

FWIW, gdb will notice when the program it's debugging changes underneath it, though only on a restart of that program. This is the behavior I'm trying to replicate in pdb.

Answer 1

The following mini-module may help. If you import it in your pdb session, then you can use:

pdb> pdbs.r()

at any time to force-reload all non-system modules except main. The code skips that because it throws an ImportError('Cannot re-init internal module main') exception.

# pdbs.py - PDB support

from __future__ import print_function

def r():
    """Reload all non-system modules, to reload stuff on pbd restart. """
    import importlib
    import sys

    # This is likely to be OS-specific
    SYS_PREFIX = '/usr/lib'

    for k, v in list(sys.modules.items()):
        if (
            k == "__main__" or
            k.startswith("pdb") or
            not getattr(v, "__file__", None)
            or v.__file__.startswith(SYS_PREFIX)
        ):
            continue
        print("reloading %s [%s]" % (k, v.__file__), file=sys.stderr)
        importlib.reload(v)