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gh-139940: Handle RuntimeError when attaching to a non-existing process in pdb.py #139941

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gh-139940: Handle RuntimeError when attaching to a non-existing process in pdb.py #139941

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Handle RuntimeError when attaching to a process in pdb.py
frostming Oct 11, 2025
e4cf4cc
📜🤖 Added by blurb_it.
blurb-it[bot] Oct 11, 2025
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5 changes: 5 additions & 0 deletions Lib/pdb.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3577,6 +3577,11 @@ def main():
parser.error("argument -m: not allowed with argument --pid")
try:
attach(opts.pid, opts.commands)
except RuntimeError as e:
while e.__context__ is not None:
e = e.__context__
print(f"Error attaching to process: {e}")
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Why do you need to get e here? We have opts.pid here to inform the user. I don't think the user understands this. I think the proper way here is to figure out what are the possibilities for RuntimeError. We should just let the user know that this failed, and the highest possibility is that the process does not exist.

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@frostming frostming Oct 13, 2025 •
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Oh, this is just borrowed from

cpython/Lib/asyncio/tools.py

Lines 239 to 248 in 419441a

def _get_awaited_by_tasks(pid: int) -> list:
try:
return get_all_awaited_by(pid)
except RuntimeError as e:
while e.__context__ is not None:
e = e.__context__
print(f"Error retrieving tasks: {e}")
sys.exit(1)
except PermissionError as e:
exit_with_permission_help_text()
to make them symmetric.

The idea here is to hide the traceback as it may contain 3+ frames that users don't know how to handle, and at the same time, don't arbitrarily cover up any fatal errors. And only the top-most frame is the real cause.

But I am okay to change to a better way.

sys.exit(1)
except PermissionError as e:
exit_with_permission_help_text()
return
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2025-10-11-09-07-06.gh-issue-139940.g54efZ.rst
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@@ -0,0 +1 @@
Print clearer error message when using pdb to attaching to a non-existing process on Linux.
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