[Bug c++/48859] New: Regression: incorrect "uninitialized const member" error on new without new-initializer

[Bug c++/48859] New: Regression: incorrect "uninitialized const member" error on new without new-initializer

[jyasskin at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48859

           Summary: Regression: incorrect "uninitialized const member"
                    error on new without new-initializer
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: jyasskin@gcc.gnu.org


$ cat test.cc
struct HasConstructor {
  HasConstructor() {}
};

class ConstMember {
  const HasConstructor empty_;
};

void foo() {
  new ConstMember;
}
$ g++-mp-4.5 -c test.cc
$ g++-mp-4.6 -c test.cc
test.cc: In function 'void foo()':
test.cc:10:7: error: uninitialized const member in 'class ConstMember' using
'new' without new-initializer
test.cc:6:24: note: 'ConstMember::empty_' should be initialized
$ 


[expr.new]p15 says, "If the new-initializer is omitted: If T is a (possibly
cv-qualified) non-POD class type (or array thereof), the object is
default-initialized (8.5) If T is a const-qualified type, the underlying class
type shall have a user-declared default constructor."

T is ConstMember and is not const-qualified, so the object is
default-initialized.

[dcl.init]p5 says, "To default-initialize an object of type T means: if T is a
non-POD class type (clause 9), the default constructor for T is called (and the
initialization is ill-formed if T has no accessible default constructor);"

[class.ctor]p7 says, "The implicitly-defined default constructor performs the
set of initializations of the class that would be performed by a user-written
default constructor for that class with an empty mem- initializer-list (12.6.2)
and an empty function body. If that user-written default constructor would be
ill- formed, the program is ill-formed."

The empty user-written default constructor for ConstMember is well-formed, and
I don't see any other wording saying that const members prevent the creation of
a default constructor. Further, a local variable with no initializer
successfully compiles. So I believe gcc-4.6 is wrong here and gcc-4.5 was
right.

I don't see anything in the C++0x draft that would change the right behavior
here.

The workaround, of course, is to define the empty default constructor in
ConstMember. (In C++0x mode, "=default" does not work around the problem.)

[Bug c++/48859] Regression: incorrect "uninitialized const member" error on new without new-initializer

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48859

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2011-05-04 00:03:08 UTC ---
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29043
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25811

[Bug c++/48859] [4.6/4.7 Regression] incorrect "uninitialized const member" error on new without new-initializer

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48859

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-05-04 12:33:38 UTC ---
(In reply to comment #0)
> 
> The workaround, of course, is to define the empty default constructor in
> ConstMember.

Or simply add an empty new-initializer, which works when you can't change the
definition of ConstMember

[Bug c++/48859] [4.6/4.7 Regression] incorrect "uninitialized const member" error on new without new-initializer

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48859

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2011.05.04 12:32:05
                 CC|                            |fabien.chene at gmail dot
                   |                            |com
            Summary|Regression: incorrect       |[4.6/4.7 Regression]
                   |"uninitialized const        |incorrect "uninitialized
                   |member" error on new        |const member" error on new
                   |without new-initializer     |without new-initializer
     Ever Confirmed|0                           |1

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-05-04 12:32:05 UTC ---
Fabien, could you take a look? I think Andrew's right that this was caused by
the patch for PR 25811

[Bug c++/48859] [4.6/4.7 Regression] incorrect "uninitialized const member" error on new without new-initializer

[fabien at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48859

fabien at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |fabien at gcc dot gnu.org
         AssignedTo|unassigned at gcc dot       |fabien at gcc dot gnu.org
                   |gnu.org                     |

--- Comment #4 from fabien at gcc dot gnu.org 2011-05-04 13:52:27 UTC ---
(In reply to comment #2)
> Fabien, could you take a look? I think Andrew's right that this was caused by
> the patch for PR 25811

Sure.

[Bug c++/48859] [4.6/4.7 Regression] incorrect "uninitialized const member" error on new without new-initializer

[fabien at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48859

--- Comment #5 from fabien at gcc dot gnu.org 2011-05-09 17:42:24 UTC ---
Author: fabien
Date: Mon May  9 17:42:21 2011
New Revision: 173583

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=173583
Log:
Fix PR C++/48859

Added:
    trunk/gcc/testsuite/g++.dg/init/pr48859.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/init.c
    trunk/gcc/testsuite/ChangeLog

[Bug c++/48859] [4.6/4.7 Regression] incorrect "uninitialized const member" error on new without new-initializer

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48859

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-05-09 18:01:37 UTC ---
Thanks, Fabien!

N.B. the svn commit message should be the ChangeLog entry (look at the svn log
for any file to see what's normally done)

[Bug c++/48859] [4.6/4.7 Regression] incorrect "uninitialized const member" error on new without new-initializer

[fabien at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48859

fabien at gcc dot gnu.org changed:

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

--- Comment #7 from fabien at gcc dot gnu.org 2011-05-10 08:15:17 UTC ---
(In reply to comment #6)
> Thanks, Fabien!
> 
> N.B. the svn commit message should be the ChangeLog entry (look at the svn log
> for any file to see what's normally done)

Oups, sorry. I would be careful next time.

[Bug c++/48859] [4.6/4.7 Regression] incorrect "uninitialized const member" error on new without new-initializer

[jyasskin at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48859

--- Comment #8 from Jeffrey Yasskin <jyasskin at gcc dot gnu.org> 2011-05-10 15:42:54 UTC ---
Thanks! Is this patch ok for the 4.6 branch too? If you don't have time to
backport it, I can.

[Bug c++/48859] [4.6/4.7 Regression] incorrect "uninitialized const member" error on new without new-initializer

[fabien at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48859

--- Comment #9 from fabien at gcc dot gnu.org 2011-05-10 16:27:42 UTC ---
(In reply to comment #8)
> Thanks! Is this patch ok for the 4.6 branch too? 

Yes, as it is a 4.6 regression, and Jason also approved it for 4.6.

> If you don't have time to backport it, I can.

I was planning to backport it this evening, thanks.

[Bug c++/48859] [4.6/4.7 Regression] incorrect "uninitialized const member" error on new without new-initializer

[fabien at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48859

--- Comment #10 from fabien at gcc dot gnu.org 2011-05-11 06:03:42 UTC ---
Author: fabien
Date: Wed May 11 06:03:38 2011
New Revision: 173644

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=173644
Log:
gcc/cp/ChangeLog:

2011-05-11  Fabien Chene  <fabien@gcc.gnu.org>
    PR c++/48859
    * init.c (diagnose_uninitialized_cst_or_ref_member_1): stop the
    recursion if there is user defined constructor.

gcc/testsuite/ChangeLog:

2011-05-11  Fabien Chene  <fabien@gcc.gnu.org>
    PR c++/48859
    * g++.dg/init/pr48859.C: New.


Added:
    branches/gcc-4_6-branch/gcc/testsuite/g++.dg/init/pr48859.C
Modified:
    branches/gcc-4_6-branch/gcc/cp/ChangeLog
    branches/gcc-4_6-branch/gcc/cp/init.c
    branches/gcc-4_6-branch/gcc/testsuite/ChangeLog