Re: [V5][PATCH 2/2] Update documentation to clarify a GCC extension

[Jakub Jelinek <jakub@redhat.com>]

On Mon, Mar 27, 2023 at 01:38:34PM +0000, Qing Zhao wrote:
> 
> 
> > On Mar 23, 2023, at 4:14 PM, Joseph Myers <joseph@codesourcery.com> wrote:
> > 
> > On Thu, 23 Mar 2023, Qing Zhao via Gcc-patches wrote:
> > 
> >> +Wgnu-variable-sized-type-not-at-end
> >> +C C++ Var(warn_variable_sized_type_not_at_end) Warning
> >> +Warn about structures or unions with C99 flexible array members are not
> >> +at the end of a structure.
> > 
> > I think there's at least one word missing here, e.g. "that" before "are".
> 
> Will fix it.
> > 
> >> +Please use warning option  @option{-Wgnu-variable-sized-type-not-at-end} to
> >> +identify all such cases in the source code and modify them.  This extension
> >> +will be deprecated from gcc in the next release.
> > 
> > We don't generally say "in the next release" in the manual (or "deprecated 
> > from gcc").  Maybe it *is* deprecated, maybe it will be *removed*, or will 
> > *start to warn by default*, in some specified version number (giving a 
> > version number seems better than "next release"), but "will be deprecated" 
> > is odd.
> How about the following:
> 
> +Please use warning option  @option{-Wgnu-variable-sized-type-not-at-end} to

This is certainly misnamed.  GNU variable sized type not at the end of a
struct is something like
void bar (void *);
void foo (int n) {
  struct S { int a; int b[n]; int c; } s;
  s.a = 1;
  __builtin_memset (s.b, 0, sizeof (s.b));
  s.c = 3;
  bar (&s);
}
Certainly not flexible array members in the middle of structure.

> +identify all such cases in the source code and modify them.  This warning will be 
> + on by default starting from GCC14.

	Jakub