Better diagnostic for shadowed function?

[NightStrike]

On Wed, Jan 12, 2022 at 5:06 AM Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
>
> On Wed, 12 Jan 2022 at 06:34, NightStrike via Gcc-help
> <gcc-help@gcc.gnu.org> wrote:
> >
> > I recently hit this problem:
> >
> > #include <strings.h>
> > void f() {
> >     index[0] = 0;
> > }
> >
> > #gcc is 11.2.0
> > gcc -c a.c
> > a.c:4:7: error: subscripted value is neither array nor pointer nor vector
> >     4 |  index[1] = 0;
> >       |       ^
> >
> > -Wshadow (or all or extra) did not highlight that "index" was actually
> > a function from strings.h.  For the future, is there anything I could
> > have done to make gcc tell me what the real error was?
>
> g++ is *slightly* more help:
> s.c:3:10: error: invalid types ‘<unresolved overloaded function
> type>[int]’ for array subscript
>
> This at least gives you a hint it's a function, so probably declared
> somewhere in a header. The C front end could do the same, saying
> "subscripted value is a function", but it just has a generic
> diagnostic for all un-subscriptable types. Asking for that to be
> improved seems like a good use of a bugzilla PR.
>
> Maybe would make sense for us to also add a note telling you where
> 'index' was declared, as long as it doesn't get suppressed without
> -Wsystem-headers !

Added as https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103996

Thanks!