Segher Boessenkool <segher@xxxxxxxxxxxxxxxxxxx> writes:
> On Tue, May 18, 2021 at 07:45:14PM -0500, Segher Boessenkool wrote:
>> On Wed, May 19, 2021 at 10:26:22AM +1000, Michael Ellerman wrote:
>> > Guenter Roeck <linux@xxxxxxxxxxxx> writes:
>> > > Ah, sorry. I wasn't aware that the following is valid C code
>> > >
>> > > void f1()
>> > > {
>> > > return f2();
>> > > ^^^^^^
>> > > }
>> > >
>> > > as long as f2() is void as well. Confusing, but we live and learn.
>> >
>> > It might be valid, but it's still bad IMHO.
>> >
>> > It's confusing to readers, and serves no useful purpose.
>>
>> And it actually explicitly is undefined behaviour in C90 already
>> (3.6.6.4 in C90, 6.8.6.4 in C99 and later).
We use gnu89, which presumably does not make it UB.
> ... but there is a GCC extension that allows this by default:
> <https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wreturn-type>
> For C only, warn about a 'return' statement with an expression in a
> function whose return type is 'void', unless the expression type is
> also 'void'. As a GNU extension, the latter case is accepted
> without a warning unless '-Wpedantic' is used.
There's no chance we'll ever enable -Wpedantic, so I guess it's allowed
for practical purposes. I guess clang must accept it too or we'd be
seeing warnings from it.
cheers
