[Bug libstdc++/30578] New: array_allocator can't be safely copied

[Bug libstdc++/30578] New: array_allocator can't be safely copied

[skottmckay at gmail dot com]

The current implementation of the array_allocator allows the allocator to be
copy constructed. This leads to trouble due to _M_used, which is not
synchronized between the copies. Each copy will start allocating from the same
point in the underlying array.


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           Summary: array_allocator can't be safely copied
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: skottmckay at gmail dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30578

[Bug libstdc++/30578] array_allocator can't be safely copied

[skottmckay at gmail dot com]

------- Comment #1 from skottmckay at gmail dot com  2007-01-24 20:02 -------
Created an attachment (id=12950)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=12950&action=view)
Example code showing overwriting of array when copied.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30578

[Bug libstdc++/30578] array_allocator can't be safely copied

[bkoz at gcc dot gnu dot org]

------- Comment #2 from bkoz at gcc dot gnu dot org  2007-02-01 12:20 -------

Should array_allocator be copy-constructable? I am not sure that the extra
effort to make _M_used shared in a mt-safe manner is worth it, for something
that is supposed to be write-once memory. 

This is a deviation from the normal allocator interface, though.

Interesting.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30578

[Bug libstdc++/30578] array_allocator can't be safely copied

[bkoz at gcc dot gnu dot org]

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bkoz 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         |2007-02-01 13:01:04
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30578

[Bug libstdc++/30578] array_allocator can't be safely copied

[skottmckay at gmail dot com]

------- Comment #3 from skottmckay at gmail dot com  2007-02-07 21:58 -------
Doesn't it need to be copy constructable for the rebinding to work for
_Vector_base::_Vector_impl::_Tp_alloc_type?

I agree that making it mt-safe doesn't quite fit with its intended usage.

Possibly the array_allocator and backing array should be wrapped with a
non-copyable class. 


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30578