Undefined behavior in `struct.unpack`

[kumaraditya303]

Reproducer:

import struct
struct.unpack('!q', b'\xff\xff\xff\xff\xff\xff\xff\xff')

Error:

Modules/_struct.c:842:15: runtime error: left shift of 72057594037927935 by 8 places cannot be represented in type 'long long int'

Compiler options:

./configure -C --with-pydebug --with-address-sanitizer --with-undefined-behavior-sanitizer 

Python version: Python 3.12.0a0 (heads/main:30cc1901efa, Sep 10 2022, 10:14:58) [GCC 9.4.0] on linux

[kumaraditya303]

cc @mdickinson

[mdickinson]

@kumaraditya303 Thanks; this should be an easy fix.

[mdickinson]

Fixed for 3.12 in #96739. I agree with @matthiasgoergens that it's not worth fixing in 3.10 and 3.11, because the issue doesn't manifest itself in release builds, where -fwrapv is used.