Am Samstag, dem 27.07.2024 um 00:26 +0200 schrieb Alejandro Colomar:

On Sat, Jul 27, 2024 at 12:03:20AM GMT, Martin Uecker wrote:

quoted

quoted

Maybe if GNU C compilers (GCC and Clang) add it first as an extension,
adding diagnostics, it would help.

Both GCC and Clang already have such diagnostics and/or run-time checks:

https://godbolt.org/z/MPnxqb9h7

Hi Martin,

I guess that's prior art enough to make this UB in ISO C.  Is there any
paper for this already?  Does any of your paper cover that?  Should I
prepare one?

What do you mean by "this"?  Adding UB would likely see a lot
of opposition, even where this could enable run-time checks.  

N2906 would make 

int foo(char f[4]);
int foo(char f[5]);

a constraint violation (although having those types be incompatible
could also cause UB indirectly, this would not be its main effect).

So I think brining a new version of this paper forward would be
a possible next step, addressing the issues raised in the past.

Martin