[Bug c/93812] [9/10 Regression] ICE in get_constant, at c-family/c-format.c:325

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93812

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The problem is that c-format.c assumes that when the "format" attribute is
present, handle_format_attribute has already verified it and it was ok.
Unfortunately, that is not the case, because if the attribute appears on a
!prototype_p function declaration, then fewer checks are performed on it
compared to when it appears on a prototype_p function, and if the !prototype_p
function decl is then merged with a prototype_p function decl, nothing performs
the checking.
So, one way out of this is drop the validated_p stuff and always validate,, it
will then behave similarly to how:
__attribute__((nonnull(2))) void foo (void);
warns and doesn't add the attribute, but
__attribute__((nonnull(2))) void bar ();
void bar (void);
adds it silently (but in this case I believe it doesn't ICE when actually using
the attribute).
Another possibility would be to repeat the checking of the attributes which
need positional_argument (nonnull, format*, alloc_size, alloc_align) when
merging a !prototype_p decl with prototype_p one.