Re: How can Autoconf help with the transition to stricter compilation defaults?

[Paul Eggert <eggert@cs.ucla.edu>]

On 2022-11-16 06:26, Michael Matz wrote:
> char foobar(void);
> int main(void) {
>    return &foobar != 0;
> }

That still has undefined behavior according to draft C23, which says 
behavior is undefined when foobar is (say) 'memset_explicit' because the 
declaration 'char memset_explicit(void);' disagrees with draft C23's 
declaration of 'memset_explicit'. It doesn't matter whether there's a 
call to 'memset_explicit'. See draft C23 §6.2.7, which says "All 
declarations that refer to the same object or function shall have 
compatible type; otherwise, the behavior is undefined."

If Clang's threatened pickiness were of some real use elsewhere, it 
might be justifiable for default Clang to break Autoconf. But so far we 
haven't seen real-world uses that would justify this pickiness for 
Autoconf's use of 'char memset_explicit(void);'.