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Multi-line arguments in a function call crashes CPython #101928
Description
Crash report
In a function call, if one argument is split in two lines, CPython crashes. For example, we split the lambda expression, i.e., lamda_exp=lambda:1, in test2.py into two lines (See test1.py) . CPython reports a segmentation fault.
This crash just occurs on the latest main branch(e.g.commit a1f08f5, 8a2b7ee ). The older version of CPython(e.g. CPython 3.10.8, CPython 3.9.0 ) does not report any crash.
test1.py (Segmentation fault)
def foo(param, lambda_exp):
pass
foo(param=0,
lambda_exp=lambda:
1)
test2.py (work well )
def foo(param, lambda_exp):
pass
foo(param=0,
lambda_exp=lambda:1)
Error messages
Segmentation Fault
Your environment
- CPython versions tested on: main branch from GitHub (commit a1f08f5)
- Operating system and architecture: Ubuntu 18.04
Activity
[-]Multi-line arguments in function call crashes CPython[/-][+]Multi-line arguments in a function call crashes CPython[/+]hauntsaninja commentedon Feb 15, 2023
Thanks for the report! I bisected this to #101633 cc @penguin-wwy @iritkatriel
iritkatriel commentedon Feb 15, 2023
Thank you @hauntsaninja.
I see the problem - we are now creating a basicblock with
RETURN_CONST followed by NOP, and the redundant NOP is not being removed before propagate_line_numbers() uses BB_HAS_FALLTHROUGH on the block, which only looks at the last instruction to see if it exits the block.
Possible fixes:
I'll fix it tomorrow if nobody else will beat me to it.
penguin-wwy commentedon Feb 15, 2023
@iritkatriel Thanks for the fix suggestion, I tried to fix it using the first method and it seems to have minimal impact and is effective.
gh-101928: fix crash in compiler on multi-line lambda in function call (
iritkatriel commentedon Feb 16, 2023
Thanks for the report @xiaxinmeng, and for the fix @penguin-wwy .