[Bug c/66425] (void) cast doesn't suppress __attribute__((warn_unused_result))

["filbranden at google dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66425

--- Comment #22 from Filipe Brandenburger <filbranden at google dot com> ---
(In reply to Jan Engelhardt from comment #20)
> Seems like the short route is to add a new attribute
> ((warn_unused_result_with_void_cancelling)) that exhibits the "desired"
> behavior of (void) cancelling the warning, and then make glibc use that.
> Simple, no?

I'd rather see ((warn_unused_result_without_void_cancelling)).

Or, better yet, add both in and add a command-line flag to allow
((warn_unused_result)) to use one or the other.

I still don't see the point of preventing (void) from cancelling it since you
can just store the result on an otherwise unused "discard" variable, I mean, if
the programmer *really* wants to ignore the result, they can do it in many
ways, ((warn_unused_result)) is to prevent programming mistakes where the
programmer *meant* to look at the results but mistakenly forgot it...

I also fail to see what else a void cast can mean other than explicitly
indicating that the programmer *knows* the function returns a non-empty value
but decided to ignore it...

Anyways, let's not go on that rant again... If you get to implement the new
attribute that would be awesome!

Cheers,
Filipe