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Re: [Patch to gcc/function] PR 58362


On Mon, Sep 9, 2013 at 5:13 AM, Richard Biener <rguenther@suse.de> wrote:
> On Mon, 9 Sep 2013, Paolo Carlini wrote:
>
>> On 09/09/2013 12:04 PM, Richard Biener wrote:
>> > On Mon, 9 Sep 2013, Jakub Jelinek wrote:
>> >
>> > > On Mon, Sep 09, 2013 at 11:45:08AM +0200, Richard Biener wrote:
>> > > > Well, in this case the patch should IMHO be a no-op.
>> > > >
>> > > > -      warning (OPT_Wunused_parameter, "unused parameter %q+D", decl);
>> > > > +      warning_at (DECL_SOURCE_LOCATION (decl), OPT_Wunused_parameter,
>> > > > +                 "unused parameter %qD", decl);
>> > > >
>> > > > no?  Unless I misunderstand what %q+D should do.
>> > > The question is how exactly is %q+D defined, if it is
>> > > warning_at (location_of (decl), OPT_Wunused_parameter, "unused parameter
>> > > %qD", decl); in this case, or
>> > > DECL_SOURCE_LOCATION (decl) instead.
>> > It can't be 'location_of' because that's a C++ FE speciality but
>> > warning_at and %q+D are diagnostic machinery level.
>> Everything happens via call backs. Thus from the generic diagnostic machinery,
>> you go to cp_printer for C++, thus location_of for C++. In C is different, but
>> again there is, evidently, a mechanism which uses DECL_CONTEXT for PARM_DECLs
>> which leads to an inaccurate location when we *really* want the location of
>> the parameter (exactly as I explained for C++).
>
> I understand that.  But I question it.  Why would that ever be useful?
> Can't the places that want that simply use warning/error_at with the
> proper location?

I agree with Richard that if you want a locus that is not the current locus,
and is not the locus of the decl, you should use the _at version.

-- Gaby


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