[Bug c++/33984] New: [4.2/4.3 Regression] bit-fields, references and overloads

[Bug c++/33984] New: [4.2/4.3 Regression] bit-fields, references and overloads

[andrew dot stubbs at st dot com]

The following C++ program should not compile:

struct S {
  unsigned int bar : 3;
} s;

int foo(unsigned int &);
int foo(double);

int
main ()
{
  return foo(s.bar);  // invalid
}

According to the C++ standard, clause 13.3.3.1.4, paragraph 4, the 'bar' should
match against 'foo(unsigned int &)' because both use unsigned int, not the
alternative overload, 'foo(double)'. However, it should then fail because a
bit-field may not be bound to a reference.

GCC 4.1.1 and 4.1.2 did this correctly.

GCC 4.2.0+ silently accept it. The call is incorrectly bound to foo(double).


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           Summary: [4.2/4.3 Regression] bit-fields, references and
                    overloads
           Product: gcc
           Version: 4.3.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: andrew dot stubbs at st dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33984

[Bug c++/33984] [4.2/4.3 Regression] bit-fields, references and overloads

[rguenth at gcc dot gnu dot org]

------- Comment #1 from rguenth at gcc dot gnu dot org  2007-11-02 18:45 -------
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         |2007-11-02 18:45:22
               date|                            |
   Target Milestone|---                         |4.2.3


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33984

[Bug c++/33984] [4.2/4.3 Regression] bit-fields, references and overloads

[mmitchel at gcc dot gnu dot org]

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mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33984

[Bug c++/33984] [4.2/4.3 Regression] bit-fields, references and overloads

[janis at gcc dot gnu dot org]

------- Comment #2 from janis at gcc dot gnu dot org  2007-11-12 18:04 -------
The mainline patch that caused this test to be accepted:

    http://gcc.gnu.org/viewcvs?view=rev&rev=113199

    r113199 | mmitchel | 2006-04-23 18:04:33 +0000 (Sun, 23 Apr 2006)


-- 

janis at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mmitchel at gcc dot gnu dot
                   |                            |org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33984

[Bug c++/33984] [4.2/4.3 Regression] bit-fields, references and overloads

[jakub at gcc dot gnu dot org]

------- Comment #3 from jakub at gcc dot gnu dot org  2007-11-29 15:14 -------
Created an attachment (id=14668)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14668&action=view)
gcc43-pr33984.patch

I've tried to fix this by the attached patch.
standard_conversion also uses is_bitfield_expr_with_lowered_type, but
reference_binding was not.  Additionally, I've noticed that the 2006 change in
layout_class_type dropped all qualifiers from the bitfield's type if
c_build_bitfield_integer_type needs to be used.
Unfortunately this causes a regression on g++.old-deja/g++.robertl/eb5.C
- to type in this case is also the lowered bitfield type, so it fails.

Mark, any ideas?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33984

[Bug c++/33984] [4.2/4.3 Regression] bit-fields, references and overloads

[aoliva at gcc dot gnu dot org]

------- Comment #4 from aoliva at gcc dot gnu dot org  2008-01-17 12:43 -------
Mine


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aoliva at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |aoliva at gcc dot gnu dot
                   |                            |org
         AssignedTo|unassigned at gcc dot gnu   |aoliva at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33984

[Bug c++/33984] [4.2/4.3 Regression] bit-fields, references and overloads

[aoliva at gcc dot gnu dot org]

------- Comment #5 from aoliva at gcc dot gnu dot org  2008-01-17 18:01 -------
Created an attachment (id=14959)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14959&action=view)
Slight revision of Jakub's patch that fixes the regression

Getting built-in candidate functions not to use the bit-field types fixed the
regression Jakub noticed in his patch, and keeps the progression in place.  I'm
almost done testing this, and I'll post it to gcc-patches then.


-- 

aoliva at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #14668|0                           |1
        is obsolete|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33984

[Bug c++/33984] [4.2/4.3 Regression] bit-fields, references and overloads

[mark at codesourcery dot com]

------- Comment #6 from mark at codesourcery dot com  2008-01-20 20:28 -------
Subject: Re:  [4.2/4.3 Regression] bit-fields, references and
 overloads

aoliva at gcc dot gnu dot org wrote:
> ------- Comment #5 from aoliva at gcc dot gnu dot org  2008-01-17 18:01 -------
> Created an attachment (id=14959)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14959&action=view)
>  --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=14959&action=view)
> Slight revision of Jakub's patch that fixes the regression
> 
> Getting built-in candidate functions not to use the bit-field types fixed the
> regression Jakub noticed in his patch, and keeps the progression in place.  I'm
> almost done testing this, and I'll post it to gcc-patches then.

Thank you for working on this.  I think this is the right idea, but I
have two comments:

* In add_builtin_candidates, I think you can just do:

  argtypes[i] = unlowered_expr_type (lvalue_type (args[i]));

* In layout_class_type, I understand that you're trying to preserve
cv-qualification.  I don't see a test case for that, though.  If there's
a bug you're fixing here, let's have a test case for it.

Thanks,


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33984

[Bug c++/33984] [4.2/4.3 Regression] bit-fields, references and overloads

[aoliva at gcc dot gnu dot org]

------- Comment #7 from aoliva at gcc dot gnu dot org  2008-01-22 06:44 -------
Responded on gcc-patches, with revised patch.
http://gcc.gnu.org/ml/gcc-patches/2008-01/msg00988.html


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33984

[Bug c++/33984] [4.2/4.3 Regression] bit-fields, references and overloads

[aoliva at gcc dot gnu dot org]

------- Comment #8 from aoliva at gcc dot gnu dot org  2008-01-23 01:51 -------
Fixed.


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aoliva at gcc dot gnu dot org changed:

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33984

[Bug c++/33984] [4.2/4.3 Regression] bit-fields, references and overloads

[aoliva at gcc dot gnu dot org]

------- Comment #9 from aoliva at gcc dot gnu dot org  2008-01-23 01:51 -------
Subject: Bug 33984

Author: aoliva
Date: Wed Jan 23 01:50:45 2008
New Revision: 131751

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=131751
Log:
gcc/cp/ChangeLog:
PR c++/33984
* call.c (reference_binding): For bitfields use the declared bitfield
type.
(add_builtin_candidates): Likewise.
* class.c (layout_class_type): For bitfields copy over the
original type quals.
gcc/testsuite/ChangeLog:
PR c++/33984
* g++.dg/conversion/bitfield7.C: New test.
* g++.dg/cpp0x/decltype4.C: Fixed xfail.

Added:
    trunk/gcc/testsuite/g++.dg/conversion/bitfield7.C
Modified:
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/call.c
    trunk/gcc/cp/class.c
    trunk/gcc/testsuite/ChangeLog
    trunk/gcc/testsuite/g++.dg/cpp0x/decltype4.C


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33984