Re: [PATCH] PR28901 -Wunused-variable ignores unused const initialised variables

[Manuel LÃpez-IbÃÃez <lopezibanez at gmail dot com>]

On 13/09/15 13:40, Mark Wielaard wrote:
> On Sun, Sep 13, 2015 at 12:00:51AM +0200, Mark Wielaard wrote:
> > I'll rewrite my patch a little, add some C++ testcases, and update the
> > documentation. Then we can discuss again.
>
> Slightly adjusted patch attached. Now it is explicit that the warning is
> enabled by -Wunused-variable for C, but not C++. There are testcases for
> both C and C++ to check the defaults. And the hardcoded override is
> removed for C++, so the user could enable it if they want.

> +  /* -Wunused-variable implies -Wunused-const-variable for C, but not
> +     for C++, because const variables take the place of #defines in C++.  */
> +  if (warn_unused_const_variable_set == -1)
> +    warn_unused_const_variable_set = (warn_unused_variable
> +				      && ! c_dialect_cxx ());
> +

Can't you use LangEnabledBy() in c.opt to implement this? If not, I think this 
would be a regression or a bug.

Ideally, all options dependences should be encoded in the .opt files, however, 
it cannot handle yet conditions such as (cxx_dialect >= cxx11 || flag_isoc99). 
But it can handle a lot of other things already. See 
https://gcc.gnu.org/onlinedocs/gccint/Option-properties.html

Cheers,

Manuel.