[Bug c++/35782] New: support for standard layout types

[Bug c++/35782] New: support for standard layout types

[bkoz at gcc dot gnu dot org]

This is an enhancement request for a C++0x feature, standard layout type. This
is a relaxation of POD, and allows things like member functions.

This is necessary to correctly implement 29_atomics.

See:
"Modification to the definition of plain old data"
http://en.wikipedia.org/wiki/C%2B%2B0x

or

POD's Revisited
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2342.htm


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           Summary: support for standard layout types
           Product: gcc
           Version: 4.4.0
            Status: UNCONFIRMED
          Severity: enhancement
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: bkoz at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35782

[Bug c++/35782] support for standard layout types

[bkoz at gcc dot gnu dot org]

------- Comment #1 from bkoz at gcc dot gnu dot org  2008-04-01 04:05 -------

struct b
{
  bool t;

#if 1
  // need standard layout relaxation from POD
private:
  b& operator=(const b&);
  b(const b&);
#endif
};

int main()
{
  b tst1 = { false };
  const b tst2 = { true };
 return 0;
}


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35782

[Bug c++/35782] support for standard layout types

[rguenth at gcc dot gnu dot org]

------- Comment #2 from rguenth at gcc dot gnu dot org  2008-04-01 19:20 -------
Confirmed.


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rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2008-04-01 19:20:05
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35782

[Bug c++/35782] support for standard layout types

[bkoz at gcc dot gnu dot org]

------- Comment #3 from bkoz at gcc dot gnu dot org  2008-09-10 01:45 -------

Specifically the qualities that I am looking for are:

1) be able to inherit from "C" POD and be standard layout
2) be able to have deleted ctor/copy ctor and be standard layout
3) able to do aggregate init when 1, 2


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35782

[Bug c++/35782] support for standard layout types

[bkoz at gcc dot gnu dot org]

------- Comment #4 from bkoz at gcc dot gnu dot org  2008-09-10 01:47 -------
Created an attachment (id=16268)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=16268&action=view)
atomics with deleter functions


Would also like to inherit instead of encapsulate, but will cross that bridge
when the rest of the bits are settled...


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35782

[Bug c++/35782] support for standard layout types

[jason at redhat dot com]

------- Comment #5 from jason at redhat dot com  2008-09-10 03:37 -------
Subject: Re:  support for standard layout types

bkoz at gcc dot gnu dot org wrote:
> Specifically the qualities that I am looking for are:
> 
> 1) be able to inherit from "C" POD and be standard layout
> 2) be able to have deleted ctor/copy ctor and be standard layout
> 3) able to do aggregate init when 1, 2

You can't have 2 and 3 under the current working paper.

http://home.twcny.rr.com/hinnant/cpp_extensions/issues_preview/lwg-active.html#845


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35782

[Bug c++/35782] support for standard layout types

[bkoz at redhat dot com]

------- Comment #6 from bkoz at redhat dot com  2008-09-10 21:46 -------
Subject: Re:  support for standard layout types


> > 1) be able to inherit from "C" POD and be standard layout
> > 2) be able to have deleted ctor/copy ctor and be standard layout
> > 3) able to do aggregate init when 1, 2
> 
> You can't have 2 and 3 under the current working paper.
> 
> http://home.twcny.rr.com/hinnant/cpp_extensions/issues_preview/lwg-active.html#845

Ah ha. Thanks.

-benjamin


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35782

[Bug c++/35782] support for standard layout types

[jason at gcc dot gnu dot org]

------- Comment #7 from jason at gcc dot gnu dot org  2008-09-17 21:17 -------
8.5.1 says "An aggregate is an array or a class (Clause 9) with ... no base
classes (Clause 10)...."

Lawrence's suggestion won't work because the copy constructor is deleted.  To
make aggregate initialization work, we need to expand the definition of
aggregate to include classes with user-provided constructors that are all
deleted.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35782

[Bug c++/35782] support for standard layout types

[jason at gcc dot gnu dot org]

------- Comment #8 from jason at gcc dot gnu dot org  2008-09-18 17:01 -------
(In reply to comment #7)
> Lawrence's suggestion won't work because the copy constructor is deleted.

It seems I was wrong about this: the wording that went into the standard
doesn't require the copy for copy-list-initialization.  Guess I need to fix the
compiler.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35782

[Bug c++/35782] support for standard layout types

[jason at gcc dot gnu dot org]

-- 

jason at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |jason at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2008-04-01 19:20:05         |2008-12-02 19:13:07
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35782

[Bug c++/35782] support for standard layout types

[jason at gcc dot gnu dot org]

------- Comment #9 from jason at gcc dot gnu dot org  2008-12-02 23:53 -------
Subject: Bug 35782

Author: jason
Date: Tue Dec  2 23:52:02 2008
New Revision: 142379

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=142379
Log:
        PR c++/35782, c++/37860
        * call.c (build_user_type_conversion_1): Remember
        list-initialization.
        (convert_like_real): Likewise.
        (build_over_call): Don't require the copy constructor
        for copy-list-initialization.
        * cp-tree.h (TARGET_EXPR_LIST_INIT_P): New macro.

        PR c++/37234
        * decl.c (cp_finish_decl): Handle =default and =delete for
        templates, too.

Added:
    trunk/gcc/testsuite/g++.dg/cpp0x/defaulted5.C
    trunk/gcc/testsuite/g++.dg/cpp0x/initlist9.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/call.c
    trunk/gcc/cp/cp-tree.h
    trunk/gcc/cp/decl.c
    trunk/gcc/testsuite/ChangeLog


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35782

[Bug c++/35782] support for standard layout types

[jason at gcc dot gnu dot org]

------- Comment #10 from jason at gcc dot gnu dot org  2008-12-02 23:53 -------
Fixed.


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jason at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35782