Report from the additional type errors for GCC 14 BoF at Cauldron

[Florian Weimer]

* Arsen Arsenović via Gcc:

> Sam James via Gcc <gcc@gcc.gnu.org> writes:
>
>> Florian Weimer via Gcc <gcc@gcc.gnu.org> writes:
>>
>>> My understanding of the consensus goes as follows:
>>>
>>> * We want to make some changes in this area for GCC 14.
>>> * We should do the same thing that Clang does: default to the relevant
>>>   -Werror= options.
>>> * Unlike regular warnings, these warnings-as-errors should also apply
>>>   to system headers.
>>> * At least implict-int and implicit-function-declaration should be
>>>   upgraded to errors in this way.
>>> * It's too early to make the () changes and bool-as-keyword from C2X
>>>   for GCC 14.
>>> * We should fix the missing scope of the int-conversion warnings
>>>   (PR109827).  Likweise for incompatible-pointer-types (PR109826).
>>>
>>> Is this summary accurate?
>>>
>>
>> I wasn't there, but this reflects my understanding & what I would've
>> said if I could've attended.
>>
>>> I think the open issues are:
>>>
>>> * Do we want to implement something else beside implicit-int and
>>>   implicit-function-declaration?  (Candidates are int-conversion and
>>>   incompatible-pointer-types, and the void vs non-void part of
>>>   return-type, maybe others as previously discussed on the list.)
>>
>> Ideally, I'd like both int-conversion + incompatible-pointer-types in
>> this cycle, but if we have to defer one, I'd say to keep int-conversion.
>
> +1, this seems reasonable.  I'm not sure I can imagine any even
> half-legitimate use for falling off the end of functions and similar, so
> perhaps we should also take return-type?  Is that part of C23?

Falling of the end of the function is legitimate if a no-return function
is called and not annotated as such, among other things.  I don't think
we should warn or error for that by default.

The issue I'm concerned about is about “return;” in a function not
returning void, or “return expr;” in a function returning void.  This
looks like related to implict int return types for functions.  It's not
part of C99.  There is no separate -W switch to control this warning.
It is on by default (as required by C99), unlike other aspects of
-Wreturn-type.

Thanks,
Florian