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Re: PING^1: [PATCH] Add TYPE_EMPTY_RECORD for C++ empty class
- From: Joseph Myers <joseph at codesourcery dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: Jason Merrill <jason at redhat dot com>, Ulrich Weigand <uweigand at de dot ibm dot com>, GCC Patches <gcc-patches at gcc dot gnu dot org>, Jakub Jelinek <jakub at redhat dot com>, Richard Biener <richard dot guenther at gmail dot com>, Markus Trippelsdorf <markus at trippelsdorf dot de>
- Date: Wed, 16 Mar 2016 00:25:43 +0000
- Subject: Re: PING^1: [PATCH] Add TYPE_EMPTY_RECORD for C++ empty class
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On Tue, 15 Mar 2016, H.J. Lu wrote:
> On Tue, Mar 15, 2016 at 3:34 PM, Joseph Myers <joseph@codesourcery.com> wrote:
> > On Tue, 15 Mar 2016, H.J. Lu wrote:
> >
> >> On Tue, Mar 15, 2016 at 2:39 PM, Joseph Myers <joseph@codesourcery.com> wrote:
> >> > I'm not sure if the zero-size arrays (a GNU extension) are considered to
> >> > make a struct non-empty, but in any case I think the tests should cover
> >> > such arrays as elements of structs.
> >>
> >> There are couple tests for structs with members of array
> >> of empty types. testsuite/g++.dg/abi/empty14.h has
> >
> > My concern is the other way round - structs with elements such as
> > "int a[0];", an array [0] of a nonempty type. My reading of the subobject
> > definition is that such an array should not cause the struct to be
> > considered nonempty (it doesn't result in any int subobjects).
>
> This is a test for struct with zero-size array, which isn't treated
> as empty type. C++ and C are compatible in its passing.
Where is the current definition of empty types you're proposing for use in
GCC? Is the behavior of this case clear from that definition?
--
Joseph S. Myers
joseph@codesourcery.com