[Bug libstdc++/51811] New: [C++0x] Incorrect incrementation/decrementation of atomic pointers

[Bug libstdc++/51811] New: [C++0x] Incorrect incrementation/decrementation of atomic pointers

[t.schuele at web dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51811

             Bug #: 51811
           Summary: [C++0x] Incorrect incrementation/decrementation of
                    atomic pointers
    Classification: Unclassified
           Product: gcc
           Version: 4.6.2
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: t.schuele@web.de


Incrementation (decrementation) of atomic pointers does not work correctly. On
an x86-64 machine the piece of code given below produces the following output
(or something similar):

0x7fffbe6d082c
0x7fffbe6d082d
0x7fffbe6d0830
0x7fffbe6d082d

There are two problems here: Firstly, the pointer is incremented by 1 and not
by sizeof(int). Secondly, the last two lines of the output should be the same.
Note that the second problem seems to be fixed in gcc-4.7-20120107, while the
first one still occurs. Thanks for your help!

----------------------------

#include <iostream>
#include <atomic>

using namespace std;

int main(int argc, char* argv[]) {
  int value = 42;
  atomic<int*> my_pointer;
  my_pointer = &value;
  cout << my_pointer++ << endl;
  cout << my_pointer << endl;
  my_pointer = &value;
  cout << ++my_pointer << endl;
  cout << my_pointer << endl;
}

[Bug libstdc++/51811] [C++0x] Incorrect incrementation/decrementation of atomic pointers

[bkoz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51811

Benjamin Kosnik <bkoz at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2012-02-03
                 CC|                            |bkoz at gcc dot gnu.org
         AssignedTo|unassigned at gcc dot       |bkoz at gcc dot gnu.org
                   |gnu.org                     |
   Target Milestone|---                         |4.7.0
     Ever Confirmed|0                           |1

--- Comment #1 from Benjamin Kosnik <bkoz at gcc dot gnu.org> 2012-02-03 19:41:00 UTC ---
Mine

[Bug libstdc++/51811] [C++0x] Incorrect incrementation/decrementation of atomic pointers

[bkoz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51811

--- Comment #2 from Benjamin Kosnik <bkoz at gcc dot gnu.org> 2012-02-03 19:49:17 UTC ---
Author: bkoz
Date: Fri Feb  3 19:49:11 2012
New Revision: 183875

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=183875
Log:
2012-02-03  Benjamin Kosnik  <bkoz@redhat.com>

    PR libstdc++/51811
    * include/bits/atomic_base.h (atomic<_Tp*>): Fix offsets.
    * testsuite/29_atomics/atomic/operators/51811.cc: New.
    * testsuite/29_atomics/atomic/operators/pointer_partial_void.cc: New.

Added:
    trunk/libstdc++-v3/testsuite/29_atomics/atomic/operators/51811.cc
   
trunk/libstdc++-v3/testsuite/29_atomics/atomic/operators/pointer_partial_void.cc
Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/include/bits/atomic_base.h

[Bug libstdc++/51811] [C++0x] Incorrect incrementation/decrementation of atomic pointers

[bkoz at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51811

Benjamin Kosnik <bkoz at gcc dot gnu.org> changed:

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

--- Comment #3 from Benjamin Kosnik <bkoz at gcc dot gnu.org> 2012-02-15 03:01:50 UTC ---

Fixed for 4.7

[Bug libstdc++/51811] [C++0x] Incorrect increment/decrement of atomic pointers

[jingyu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51811

--- Comment #4 from Jing Yu <jingyu at gcc dot gnu.org> 2012-07-20 17:28:09 UTC ---
Author: jingyu
Date: Fri Jul 20 17:27:57 2012
New Revision: 189724

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=189724
Log:
2012-07-19  Jing Yu  <jingyu@google.com>

    Backport r183875 to fix wrong atomic<_Tp*> add_fetch.
    PR libstdc++/51811, Google ref b/6702865
    * include/bits/atomic_0.h (atomic<_Tp*>): Fix offsets.
    * include/bits/atomic_2.h: Likewise.
    * testsuite/29_atomics/atomic/operators/51811.cc: New.
    * testsuite/29_atomics/atomic/operators/pointer_partial_void.cc: New.

Added:
   
branches/google/gcc-4_6/libstdc++-v3/testsuite/29_atomics/atomic/operators/51811.cc
   
branches/google/gcc-4_6/libstdc++-v3/testsuite/29_atomics/atomic/operators/pointer_partial_void.cc
Modified:
    branches/google/gcc-4_6/libstdc++-v3/ChangeLog.google-4_6
    branches/google/gcc-4_6/libstdc++-v3/include/bits/atomic_0.h
    branches/google/gcc-4_6/libstdc++-v3/include/bits/atomic_2.h