[issue44707] runtime error: applying zero offset to null pointer in Objects/listobject.c
Łukasz Langa
report at bugs.python.org
Fri Jul 23 10:43:45 EDT 2021
Łukasz Langa <lukasz at langa.pl> added the comment:
I'm still unable to reproduce this locally. Objects/listobject.c:527:24 is this line in `list_concat`:
dest = np->ob_item + Py_SIZE(a);
(permalink: https://github.com/python/cpython/blob/8f42106b5c362495f72c6ca2fa3884538e4023db/Objects/listobject.c#L527)
This can only be problematic if `ob_item` of the new list is NULL *AND* list `a` is non-empty. In practice that's impossible because if `a` is non-empty, it would already populate `np` with its elements using the for-loop right above the line in question.
So this sounds like the compiler complaining about NULL + 0 which seems unnecessary?
By the way, instead of messing with CC, it's preferred to use the --with-undefined-behavior-sanitizer option to ./configure.
We could accept Serhiy's change but I'm afraid that without a reliable way to reproduce, this will regress at some point.
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