Re: [PATCH] Add option to control warnings added through attribure "warning"

[Martin Sebor <msebor at gmail dot com>]

On 10/12/2018 04:14 AM, Nikolai Merinov wrote:
> Hello,
>
> In https://gcc.gnu.org/ml/gcc-patches/2018-09/msg01795.html mail I
> suggested patch to have ability to control behavior of
> "__attribute__((warning))" in case when option "-Werror" enabled. Usage
> example:
>
> > #include <string.h>
> > int a() __attribute__((warning("Warning: `a' was used")));
> > int a() { return 1; }
> > int main () { return a(); }
>
> > $ gcc -Werror test.c
> > test.c: In function ‘main’:
> > test.c:4:22: error: call to ‘a’ declared with attribute warning:
> > Warning: `a' was used [-Werror]
> >  int main () { return a(); }
> >                       ^
> > cc1: all warnings being treated as errors
> > $ gcc -Werror -Wno-error=warning-attribute test.c
> > test.c: In function ‘main’:
> > test.c:4:22: warning: call to ‘a’ declared with attribute warning:
> > Warning: `a' was used
> >  int main () { return a(); }
> >                       ^
> Can you provide any feedback on suggested changes?

It seems like a useful feature and in line with the philosophy
that distinct warnings should be controlled by their own options.

I would only suggest to consider changing the name to
-Wattribute-warning, because it applies specifically to that
attribute (as opposed to warnings about attributes in general).

There are many attributes in GCC and diagnosing problems that
are unique to each, under the same -Wattributes option, is
becoming too coarse and overly limiting.  To make it more
flexible, I expect new options will need to be introduced,
such as -Wattribute-alias (to control aspects of the alias
attribute and others related to it), or -Wattribute-const
(to control diagnostics about functions declared with
attribute const that violate the attribute's constraints).

An alternative might be to introduce a single -Wattribute=
<attribute-list> option where the <attribute-list> gives
the names of all the distinct attributes whose unique
diagnostics one might need to control.

Martin