https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108036
--- Comment #9 from Alejandro Colomar <alx at kernel dot org> --- Hi Lundin! On Thu, Mar 07, 2024 at 10:18:12AM +0000, daniel.lundin.mail at gmail dot com wrote: > --- Comment #8 from Daniel Lundin <daniel.lundin.mail at gmail dot com> --- > I don't believe char past_end[0] is valid C, because it is an invalid array > declaration. Unlike [] or [*] that declares an array of incomplete type. > > Since it is a function parameter, it will of course later get adjusted to a > pointer to the first element. But it still has to be a valid declaration to > begin with. Similarly, char arr[][] is invalid because it remains an > incomplete > type after adjustment (see C17 6.7.6.4 ยง4). Agree; ISO C seems to not allow this with their wording. (I wish it did, because it's just a matter of wording, not that they don't allow passing a pointer to past the end). But maybe the wording needed for allowing this would have other undersirable consequences, so I'm happy as long as GNU C would support this. > gcc does allow [0] as an extension since that was commonly used for purposes > of > implementing the "struct hack" back in the days before flexible array members > were standardized. > > The conclusion ought to be that gcc should let [0] through if compiled in > -std=gnu23 mode but not in -std=c23 and/or -pedantic. And agree; if support for this is added, pedantic or ISO C modes should complain about it. Have a lovely day! Alex
