bpo-35091: Objects/listobject.c: Don't rely on signed int overflow in…

[izbyshev]

… gallop functions

Signed integer overflow is undefined behavior.

https://bugs.python.org/issue35091

[serhiy-storchaka]

Other option is using unsigned integers. In this case additional checks could be removed. The check in the while condition would be enough.

[izbyshev]

@serhiy-storchaka If it's OK to change types of several variables in affected functions (because if only ofs is changed, we'd need to add casts all over the place to avoid signed/unsigned comparison warnings), I'll update the patch.

[serhiy-storchaka]

Added @tim-one, the author of this code.

[izbyshev]

@serhiy-storchaka, @tim-one I've implemented an alternative PR #10184 that uses size_t in gallop functions instead.

[csabella]

Merged GH-10202 as the PR approved by @tim-one, so I'll close this one.