From: "H.J. Lu" <hjl.tools@gmail.com>
To: Jason Merrill <jason@redhat.com>
Cc: Joseph Myers <joseph@codesourcery.com>,
Ulrich Weigand <uweigand@de.ibm.com>,
GCC Patches <gcc-patches@gcc.gnu.org>,
Jakub Jelinek <jakub@redhat.com>,
Richard Biener <richard.guenther@gmail.com>,
Markus Trippelsdorf <markus@trippelsdorf.de>
Subject: Re: PING^1: [PATCH] Add TYPE_EMPTY_RECORD for C++ empty class
Date: Wed, 16 Mar 2016 11:55:00 -0000 [thread overview]
Message-ID: <CAMe9rOr=0w5t_qda-E9SXy0cMVSrynU1gp3g6PuLNevihiu=KQ@mail.gmail.com> (raw)
In-Reply-To: <56E8CA16.2040206@redhat.com>
On Tue, Mar 15, 2016 at 7:51 PM, Jason Merrill <jason@redhat.com> wrote:
> On 03/15/2016 08:25 PM, Joseph Myers wrote:
>>
>> 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?
>
>
> "An empty type is a type where it and all of its subobjects (recursively)
> are of structure, union, or array type. No memory slot nor register should
> be used to pass or return an object of empty type."
>
> It seems to me that such a struct should be considered an empty type under
> this definition, since a zero-length array has no subobjects.
>
Since zero-size array is GCC extension, we can change it. Do we
want to change its passing for C?
--
H.J.
next prev parent reply other threads:[~2016-03-16 11:55 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-08 16:22 H.J. Lu
2015-12-09 14:05 ` Richard Biener
2015-12-09 18:53 ` H.J. Lu
2015-12-09 21:14 ` H.J. Lu
2015-12-09 21:31 ` Markus Trippelsdorf
2015-12-10 11:24 ` Richard Biener
2015-12-11 23:52 ` H.J. Lu
2015-12-12 14:51 ` Jason Merrill
2015-12-12 15:27 ` Jakub Jelinek
2015-12-12 16:45 ` H.J. Lu
2015-12-12 18:43 ` Marc Glisse
2015-12-14 20:16 ` Jason Merrill
2015-12-14 20:39 ` H.J. Lu
2015-12-14 20:44 ` Jason Merrill
2015-12-14 22:08 ` H.J. Lu
2016-01-26 19:27 ` Jason Merrill
2016-01-26 19:52 ` H.J. Lu
2016-01-26 20:23 ` Marc Glisse
2016-01-26 20:26 ` H.J. Lu
2016-01-26 20:44 ` Marc Glisse
2016-01-26 21:21 ` H.J. Lu
2016-01-26 21:40 ` Jakub Jelinek
2016-01-26 22:21 ` H.J. Lu
2016-01-27 8:10 ` Marc Glisse
2016-01-27 8:21 ` Jakub Jelinek
2016-01-27 9:03 ` Marc Glisse
2016-01-27 13:46 ` H.J. Lu
2016-01-27 15:39 ` H.J. Lu
2016-03-01 1:02 ` Jason Merrill
2016-03-01 22:44 ` H.J. Lu
2016-03-02 16:25 ` Ulrich Weigand
2016-03-02 17:34 ` H.J. Lu
2016-03-15 15:35 ` Jason Merrill
2016-03-15 16:00 ` H.J. Lu
2016-03-15 19:32 ` Jason Merrill
2016-03-16 12:38 ` H.J. Lu
2016-03-16 16:58 ` Jason Merrill
2016-03-16 17:02 ` H.J. Lu
2016-03-16 19:39 ` H.J. Lu
2016-03-16 19:43 ` Jason Merrill
2016-03-15 21:40 ` Joseph Myers
2016-03-15 22:31 ` H.J. Lu
2016-03-15 22:35 ` Joseph Myers
2016-03-16 0:23 ` H.J. Lu
2016-03-16 0:25 ` Joseph Myers
2016-03-16 2:17 ` H.J. Lu
2016-03-16 9:46 ` Bernhard Reutner-Fischer
2016-03-16 11:53 ` H.J. Lu
2016-03-16 2:51 ` Jason Merrill
2016-03-16 11:55 ` H.J. Lu [this message]
2016-03-16 14:33 ` Jason Merrill
2016-03-16 14:48 ` H.J. Lu
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