[quelsolaar]

Alignment only matters when you use a pointer. This is a question of if technically non compatible signatures are UB by them selves. Unaligned access is UB for sure, but even if everything is perfectly aligned they may still be UB according to the standard.

Example:

Lets say you have a function that takes a pointer to a 32 bit integer.

void my_function(int x)

But in an other file you declare it as a function taking a 32 bit float, and call it:

extern void my_function(float x); ... my_function(&my_float);

This is very likely to work in almost all implementations. float and int have the same size and same alignment requirements, but the standard may still say its UB. So it is technically UB, but may be relied upon in practice.