Hi Joseph, On Thu, Jan 15, 2026 at 11:33:10PM +0000, Joseph Myers wrote: > On Thu, 15 Jan 2026, Alejandro Colomar wrote: > > > I recently discovered that we wouldn't be introducing and new undefined > > behavior. That same undefined behavior already exists today in GCC 16: > > You can't deduce UB from how the compiler behaves on this particular > input. You need to specify the semantics so that then we can see if there > is UB either explicitly or implicitly.
Hmmmm, then we should document the behavior of _Countof() in GCC 16 for pointers to arrays when interacting with forward declarations of parameters, right? Then, array parameters would just be consistent with that. That makes sense to me. Should I document it as part of _Countof() or as part of forward declarations of parameters? Do you have any preference? Have a lovely night! Alex -- <https://www.alejandro-colomar.es>
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