[PATCH] c++: designated init of char array by string constant [PR55227]

will wray wjwray@gmail.com
Thu Nov 18 03:23:58 GMT 2021


V2 Patch
https://gcc.gnu.org/bugzilla/attachment.cgi?id=51828

On Wed, Nov 17, 2021 at 10:06 PM will wray <wjwray@gmail.com> wrote:
>
> Thanks for the review Marek;
> I'll post the updated patch in a follow-on message and on bugzilla.
>
> On Mon, Nov 15, 2021 at 8:03 PM Marek Polacek <polacek@redhat.com> wrote:
>
> > I also noticed the C++ FE rejects
> >
> >   struct A { char x[4]; };
> >   struct B { struct A a; };
> >   struct B b = { .a.x = "abc" };
> > but the C FE accepts it.  But that's for another time.
>
> Yes, the nested case is invalid for C++, valid for C.
> c.f. cppreference aggregate init.
>
> > > +      reshape_iter stripd = {};
> >
> > Since the previous variables spell it "stripped" maybe call it stripped_iter.
>
> I've left it as "stripd"; the top level reshape_iter is just "d", non-verbose,
> so "stripped_d" inappropriately over-verbose.
>
> > > @@ -6836,7 +6838,8 @@ reshape_init_r (tree type, reshape_iter *d, tree first_initializer_p,
> > >        array types (one value per array element).  */
> > >        if (TREE_CODE (stripped_str_init) == STRING_CST)
> > >       {
> > > -       if (has_designator_problem (d, complain))
> >
> > So the logic here is that...
>
> Yes, you get the logic exactly... took me a few rounds to get it.
>
> > Nice to finally remove this, but let's keep this part of the comment.
>
> Agreed, and reinstated.
>
> > BRACE_ENCLOSED_INITIALIZER_P checks that it gets a CONSTRUCTOR so you
> > can remove the first check.
>
> Nice, thanks; missed that.
>
> > > +// { dg-do compile }
> > > +// { dg-options "-pedantic" }
> >
> > FWIW, if you remove the dg-options, -pedantic-errors will be used so you could
> > drop it and then use dg-error instead of dg-warning below but this is OK too.
>
> I'd copied that from another desigN.C test, now I've copied the simpler:
>
> +// { dg-options "" }
>
> and removed all of the noisy dg-warning tests
>
> > We should probably test more:
> > - nested structs
> > - anonymous unions
> > - test when the initializer is too long
> > - multidim arrays:
>
> Cut-n-paste'd your multidim array test, and added a couple more
>
> > Hope this is useful...
>
> Very useful, thanks again


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