Re: Can we drop upstream Linux x32 support?
From: Florian Weimer
Date: Thu Dec 13 2018 - 11:05:11 EST
* Rich Felker:
>> If the compiler can handle the zeroing, that would be great, though not
>> sure how (some __attribute__((zero)) which generates a type constructor
>> for such structure; it kind of departs from what the C language offers).
> The compiler fundamentally can't. At the very least it would require
> effective type tracking, which requires shadow memory and is even more
> controversial than -fstrict-aliasing (because in a sense it's a
> stronger version thereof).
It's possible to do it with the right types. See _Bool on 32-bit Darwin
PowerPC for an example, which is four bytes instead of the usual one.
Similarly, we could have integer types with trap representations.
Whether it is a good idea is a different matter, but the amount of
compiler magic required is actually limited.