[Bug libstdc++/35969] GLIBCXX_DEBUG: list::merge triggers bad assert

[paolo at gcc dot gnu dot org]

--- Comment #7 from paolo at gcc dot gnu dot org  2008-04-24 17:03 ---
Subject: Bug 35969

Author: paolo
Date: Thu Apr 24 17:03:13 2008
New Revision: 134642

URL: http://gcc.gnu.org/viewcvs?root=gccview=revrev=134642
Log:
2008-04-24  Paolo Carlini  [EMAIL PROTECTED]

PR libstdc++/35969
* include/debug/list (merge): Use _M_transfer_iter, consistently
with the splice members.
* testsuite/23_containers/list/operations/35969.cc: New.

* testsuite/23_containers/list/operators: Rename to
testsuite/23_containers/list/operations.

Added:
trunk/libstdc++-v3/testsuite/23_containers/list/operations/
  - copied from r134503,
trunk/libstdc++-v3/testsuite/23_containers/list/operators/
trunk/libstdc++-v3/testsuite/23_containers/list/operations/35969.cc
Removed:
trunk/libstdc++-v3/testsuite/23_containers/list/operators/
Modified:
trunk/libstdc++-v3/ChangeLog
trunk/libstdc++-v3/include/debug/list


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35969

[Bug libstdc++/35969] GLIBCXX_DEBUG: list::merge triggers bad assert

[pcarlini at suse dot de]

--- Comment #8 from pcarlini at suse dot de  2008-04-24 17:05 ---
Fixed for 4.4.0.


-- 

pcarlini at suse dot de changed:

   What|Removed |Added

 Status|ASSIGNED|RESOLVED
 Resolution||FIXED
   Target Milestone|--- |4.4.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35969

[Bug libstdc++/35969] GLIBCXX_DEBUG: list::merge triggers bad assert

[pcarlini at suse dot de]

--- Comment #6 from pcarlini at suse dot de  2008-04-21 00:46 ---
According to the resolution of DR 250,

  http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#250

indeed splicing doesn't really invalidate iterators. Therefore, the debug-mode
merge should be consistent with that behavior. The fix seems easy...


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pcarlini at suse dot de changed:

   What|Removed |Added

 AssignedTo|unassigned at gcc dot gnu   |pcarlini at suse dot de
   |dot org |
 Status|UNCONFIRMED |ASSIGNED
 Ever Confirmed|0   |1
   Last reconfirmed|-00-00 00:00:00 |2008-04-21 00:46:07
   date||


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35969

[Bug libstdc++/35969] GLIBCXX_DEBUG: list::merge triggers bad assert

[greened at obbligato dot org]

--- Comment #1 from greened at obbligato dot org  2008-04-18 03:12 ---
Created an attachment (id=15493)
 -- (http://gcc.gnu.org/bugzilla/attachment.cgi?id=15493action=view)
Preprocessed source


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35969

[Bug libstdc++/35969] GLIBCXX_DEBUG: list::merge triggers bad assert

[greened at obbligato dot org]

--- Comment #2 from greened at obbligato dot org  2008-04-18 03:13 ---
Created an attachment (id=15494)
 -- (http://gcc.gnu.org/bugzilla/attachment.cgi?id=15494action=view)
Unpreprocessed source

Includes comments describing the problem.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35969

[Bug libstdc++/35969] GLIBCXX_DEBUG: list::merge triggers bad assert

[pinskia at gcc dot gnu dot org]

--- Comment #3 from pinskia at gcc dot gnu dot org  2008-04-18 03:23 ---
I don't know if the SGI website has been updated to take into account what the
C++ standard says.  Since STL was originally from HP/SGI, that page is old and
might not reflect reality any more.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35969

[Bug libstdc++/35969] GLIBCXX_DEBUG: list::merge triggers bad assert

[greened at obbligato dot org]

--- Comment #4 from greened at obbligato dot org  2008-04-18 03:26 ---
Subject: Re:  GLIBCXX_DEBUG: list::merge triggers bad
 assert

pinskia at gcc dot gnu dot org wrote:
 --- Comment #3 from pinskia at gcc dot gnu dot org  2008-04-18 03:23 
 ---
 I don't know if the SGI website has been updated to take into account what the
 C++ standard says.  Since STL was originally from HP/SGI, that page is old and
 might not reflect reality any more.

Sure.  But not everyone has a copy of the standard.  :)  Can we get a
ruling on this?


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35969

[Bug libstdc++/35969] GLIBCXX_DEBUG: list::merge triggers bad assert

[greened at obbligato dot org]

--- Comment #5 from greened at obbligato dot org  2008-04-18 04:16 ---
Ok, the closest thing I could find is the 1998 draft standard:

http://www.kuzbass.ru:8086/docs/isocpp/lib-containers.html#lib.sequences

It says that splice invalidates only the iterators and references to the
spliced elements.  There is no statement about iterators for merge.

So it seems like the testcase is invalid not due to the merge but due to the
splices.  GLIBCXX_DEBUG mode doesn't catch the problem with the splices since
the iterator is still considered valid after the splice.  For example, the
second splce doesn't assert on an invalid iterator being passed to it.

Perhaps this was changed in the final standard.  It seems odd to me that splice
and merge would invalidate iterators as iterator stability is a prime reason
for using std::list and these operations don't destroy any sequence values.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35969