[Bug c++/15471] New: Incorrect member pointer offsets in anonymous structs/unions

[Bug c++/15471] New: Incorrect member pointer offsets in anonymous structs/unions

[us15 at os dot inf dot tu-dresden dot de]

The code below outputs the addresses of member variables of class "myclass"
using a table of pointers to member variables and using an instance of
"myclass". I'd expect both methods to produce the same result, however, the
addresses of member variables x and y are wrong when applying the member
pointers to object "foo".


Compiler version:

Reading specs from /usr/lib/gcc/i486-slackware-linux/3.4.0/specs
Configured with: ../gcc-3.4.0/configure --prefix=/usr --enable-shared
--enable-threads=posix --enable-__cxa_atexit --disable-checking --with-gnu-ld
--verbose --target=i486-slackware-linux --host=i486-slackware-linux
Thread model: posix
gcc version 3.4.0

Example code to demonstrate the problem:

#include <stdio.h>

class myclass
{

public:
  union
  {
    unsigned state[5];
    struct
    {
      unsigned a;
      unsigned b;
      union
      {
        unsigned nums[2];
        struct
        {
          unsigned x, y;
        };
      };
      unsigned c;
    };
  };
};

unsigned
myclass::*
  members[] = {
  &myclass::a,
  &myclass::b,
  &myclass::x,
  &myclass::y,
  &myclass::c,
};

myclass
  foo;

int
main (void)
{
  printf ("a -> %p %p\n", &(foo.*members[0]), &foo.a);
  printf ("b -> %p %p\n", &(foo.*members[1]), &foo.b);
  printf ("x -> %p %p\n", &(foo.*members[2]), &foo.x); // differs
  printf ("y -> %p %p\n", &(foo.*members[3]), &foo.y); // differs
  printf ("c -> %p %p\n", &(foo.*members[4]), &foo.c);

  return 0;
}

-- 
           Summary: Incorrect member pointer offsets in anonymous
                    structs/unions
           Product: gcc
           Version: 3.4.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: us15 at os dot inf dot tu-dresden dot de
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: n/a
  GCC host triplet: i486-slackware-linux
GCC target triplet: i486-slackware-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15471

[Bug c++/15471] Incorrect member pointer offsets in anonymous structs/unions

[pinskia at gcc dot gnu dot org]

------- Additional Comments From pinskia at gcc dot gnu dot org  2004-05-15 21:56 -------
anonymous structs are an extension to c++ so they could act any way.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15471

[Bug c++/15471] Incorrect member pointer offsets in anonymous structs/unions

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-05-25 14:20 -------
I don't know what we're supposed to do here, but this is indeed 
surprising: 
----------------------- 
#include <stdio.h> 
 
struct myclass { 
    unsigned a; 
    union { 
        unsigned x; 
    }; 
}; 
 
int main () { 
  myclass foo; 
  unsigned myclass::* member = &myclass::x; 
  printf ("x -> %p %p\n", &(foo.*member), &foo.x); 
} 
----------------------- 
One would expect the two pointers to be the same, but they're not: 
 
g/x> /home/bangerth/bin/gcc-3.4-pre/bin/c++ x.cc ; ./a.out  
x -> 0xbfffeaa0 0xbfffeaa4 
 
It has indeed to do with the anonymous union (which in this case only 
contains a single element), since if I remove it and bring the variable 
x to the myclass scope, then the problem disappears. 
 
W. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15471

[Bug c++/15471] [3.4/3.5 Regression] Incorrect member pointer offsets in anonymous structs/unions

[giovannibajo at libero dot it]

------- Additional Comments From giovannibajo at libero dot it  2004-05-26 12:07 -------
I couldn't find the relevant paragraph in the standard, thus I am not sure this 
is actually legal code. It must be noted that EDG in strict mode accepts it and 
generates the same address for both pointers (which is by no doubt the correct 
behaviour, once we assume the code is legal).

GCC rejects this snippet up to 3.4. Since 3.4, we accept the snippet but 
generate wrong code with it. I rate this as a regression nonetheless, since 
wrong-code is much worse than what we used to do.

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |giovannibajo at libero dot
                   |                            |it
           Severity|normal                      |critical
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|                            |1
           Keywords|                            |wrong-code
      Known to fail|                            |2.95.3 3.0.4 3.3.3 3.4.0
                   |                            |3.5.0
   Last reconfirmed|0000-00-00 00:00:00         |2004-05-26 12:07:55
               date|                            |
            Summary|Incorrect member pointer    |[3.4/3.5 Regression]
                   |offsets in anonymous        |Incorrect member pointer
                   |structs/unions              |offsets in anonymous
                   |                            |structs/unions
   Target Milestone|---                         |3.4.1


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15471

[Bug c++/15471] [3.4/3.5 Regression] Incorrect member pointer offsets in anonymous structs/unions

[mmitchel at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |mark at codesourcery dot com
                   |dot org                     |
             Status|NEW                         |ASSIGNED


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15471

[Bug c++/15471] [3.4/3.5 Regression] Incorrect member pointer offsets in anonymous structs/unions

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-05-28 22:29 -------
Subject: Bug 15471

CVSROOT:	/cvs/gcc
Module name:	gcc
Branch: 	gcc-3_4-branch
Changes by:	mmitchel@gcc.gnu.org	2004-05-28 22:29:44

Modified files:
	gcc/cp         : ChangeLog decl2.c init.c name-lookup.c typeck.c 
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/g++.dg/expr: ptrmem4.C 
	gcc/testsuite/g++.dg/template: operator3.C 
	gcc/testsuite/g++.dg/warn: noeffect5.C 

Log message:
	PR c++/15083
	* decl2.c (delete_sanity): Set TREE_SIDE_EFFECTS on a DELETE_EXPR,
	even in a templat.e
	* init.c (build_new): Likewise.
	
	PR c++/15640
	* name-lookup.c (arg_assoc): Robustify.
	
	PR c++/15471
	* typeck.c (unary_complex_lvalue): Use context_for_name_lookup
	when determining the scope to use for a pointer to member.
	
	PR c++/15083
	* g++.dg/warn/noeffect5.C: New test.
	
	PR c++/15471
	* g++.dg/expr/ptrmem4.C: New test.
	
	PR c++/15640
	* g++.dg/template/operator3.C: New test.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.3892.2.107&r2=1.3892.2.108
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/decl2.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.695.4.7&r2=1.695.4.8
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/init.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.356.2.9&r2=1.356.2.10
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/name-lookup.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.34.2.12&r2=1.34.2.13
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/typeck.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.519.2.16&r2=1.519.2.17
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.3389.2.185&r2=1.3389.2.186
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/expr/ptrmem4.C.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=NONE&r2=1.1.2.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/template/operator3.C.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=NONE&r2=1.1.2.1
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/warn/noeffect5.C.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=NONE&r2=1.2.4.1



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15471

[Bug c++/15471] [3.4/3.5 Regression] Incorrect member pointer offsets in anonymous structs/unions

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-05-28 22:35 -------
Subject: Bug 15471

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	mmitchel@gcc.gnu.org	2004-05-28 22:35:50

Modified files:
	gcc/cp         : ChangeLog decl2.c init.c name-lookup.c typeck.c 
	gcc/testsuite  : ChangeLog 
Added files:
	gcc/testsuite/g++.dg/expr: ptrmem4.C 
	gcc/testsuite/g++.dg/template: operator3.C 
	gcc/testsuite/g++.dg/warn: noeffect6.C 

Log message:
	PR c++/15083
	* decl2.c (delete_sanity): Set TREE_SIDE_EFFECTS on a DELETE_EXPR,
	even in a templat.e
	* init.c (build_new): Likewise.
	
	PR c++/15640
	* name-lookup.c (arg_assoc): Robustify.
	
	PR c++/15471
	* typeck.c (unary_complex_lvalue): Use context_for_name_lookup
	when determining the scope to use for a pointer to member.
	
	PR c++/15083
	* g++.dg/warn/noeffect5.C: New test.
	
	PR c++/15471
	* g++.dg/expr/ptrmem4.C: New test.
	
	PR c++/15640
	* g++.dg/template/operator3.C: New test.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/ChangeLog.diff?cvsroot=gcc&r1=1.4064&r2=1.4065
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/decl2.c.diff?cvsroot=gcc&r1=1.709&r2=1.710
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/init.c.diff?cvsroot=gcc&r1=1.370&r2=1.371
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/name-lookup.c.diff?cvsroot=gcc&r1=1.54&r2=1.55
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/typeck.c.diff?cvsroot=gcc&r1=1.544&r2=1.545
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/ChangeLog.diff?cvsroot=gcc&r1=1.3789&r2=1.3790
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/expr/ptrmem4.C.diff?cvsroot=gcc&r1=1.1&r2=1.2
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/template/operator3.C.diff?cvsroot=gcc&r1=1.1&r2=1.2
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/testsuite/g++.dg/warn/noeffect6.C.diff?cvsroot=gcc&r1=NONE&r2=1.1



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15471

[Bug c++/15471] [3.4/3.5 Regression] Incorrect member pointer offsets in anonymous structs/unions

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-05-28 23:33 -------
Subject: Bug 15471

CVSROOT:	/cvs/gcc
Module name:	gcc
Branch: 	gcc-3_4-branch
Changes by:	mmitchel@gcc.gnu.org	2004-05-28 23:33:40

Modified files:
	gcc/cp         : ChangeLog cp-tree.h expr.c typeck.c 

Log message:
	PR c++/15471
	* typeck.c (unary_complex_lvalue): Use context_for_name_lookup
	when determining the scope to use for a pointer to member.
	(lookup_anon_field): Give it external linkage.
	* cp-tree.h (lookup_anon_field): Declare it.
	* expr.c (cplus_expand_constant): Use it.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/ChangeLog.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.3892.2.108&r2=1.3892.2.109
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/cp-tree.h.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.946.4.11&r2=1.946.4.12
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/expr.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.75.4.1&r2=1.75.4.2
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/typeck.c.diff?cvsroot=gcc&only_with_tag=gcc-3_4-branch&r1=1.519.2.17&r2=1.519.2.18



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15471

[Bug c++/15471] [3.4/3.5 Regression] Incorrect member pointer offsets in anonymous structs/unions

[cvs-commit at gcc dot gnu dot org]

------- Additional Comments From cvs-commit at gcc dot gnu dot org  2004-05-28 23:34 -------
Subject: Bug 15471

CVSROOT:	/cvs/gcc
Module name:	gcc
Changes by:	mmitchel@gcc.gnu.org	2004-05-28 23:34:39

Modified files:
	gcc/cp         : ChangeLog cp-tree.h expr.c typeck.c 

Log message:
	PR c++/15471
	* typeck.c (unary_complex_lvalue): Use context_for_name_lookup
	when determining the scope to use for a pointer to member.
	(lookup_anon_field): Give it external linkage.
	* cp-tree.h (lookup_anon_field): Declare it.
	* expr.c (cplus_expand_constant): Use it.

Patches:
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/ChangeLog.diff?cvsroot=gcc&r1=1.4065&r2=1.4066
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/cp-tree.h.diff?cvsroot=gcc&r1=1.968&r2=1.969
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/expr.c.diff?cvsroot=gcc&r1=1.77&r2=1.78
http://gcc.gnu.org/cgi-bin/cvsweb.cgi/gcc/gcc/cp/typeck.c.diff?cvsroot=gcc&r1=1.545&r2=1.546



-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15471

[Bug c++/15471] [3.4/3.5 Regression] Incorrect member pointer offsets in anonymous structs/unions

[mmitchel at gcc dot gnu dot org]

------- Additional Comments From mmitchel at gcc dot gnu dot org  2004-05-28 23:35 -------
Fixed in GCC 3.4.1.

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


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15471