> On Mar 27, 2023, at 11:43 AM, Jakub Jelinek <[email protected]> wrote:
>
> On Mon, Mar 27, 2023 at 01:38:34PM +0000, Qing Zhao wrote:
>>
>>
>>> On Mar 23, 2023, at 4:14 PM, Joseph Myers <[email protected]> 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.
The name “-Wgnu-variable-sized-type-not-at-end” was just used the warning name
from CLANG. -:)
Shall we use the same name as CLANG? Or we invent a new name?
> 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.
Right now, with -Wpedantic, we have the following warning for the above small
case:
t2.c:3:24: warning: a member of a structure or union cannot have a variably
modified type [-Wpedantic]
3 | struct S { int a; int b[n]; int c; } s;
| ^
Do we have a definition for “GNU variable sized type” now?
Shall we include "flexible array members” and" the structure/union with a
flexible array members at the end" into “GNU variable sized type”?
thanks.
Qing
>
>> +identify all such cases in the source code and modify them. This warning
>> will be
>> + on by default starting from GCC14.
>
> Jakub
