Regarding the warning in Modules/_posixsubprocess.c, I don’t see any problem. I’m not sure exactly what it is warning about. Maybe if the cur pointer ever gets _before_ the start of hex_errno, that could be a problem, but the loop should stop when it reaches the start.

The warnings in Modules/sha512module.c refer to the first line of the sha512_transform() function. I cannot see any pointer comparisons in that function. The closest is pointer and array indexing, but it all seems to be in order.

I propose to ignore these warnings.