Re: [Boost-bugs] [Boost C++ Libraries] #11801: Recursive modify in multi_index sometimes does not update index correctly

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #11801: Recursive modify in multi_index sometimes does not update index correctly
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2015-11-20 12:29:16

#11801: Recursive modify in multi_index sometimes does not update index correctly
-------------------------------------+-------------------------------------
  Reporter:  Valentyn Shtronda       |      Owner:  joaquin
  <valiko.ua@…>                      |     Status:  closed
      Type:  Bugs                    |  Component:  multi_index
 Milestone:  To Be Determined        |   Severity:  Problem
   Version:  Boost 1.59.0            |   Keywords:  multi_index
Resolution:  invalid                 |  multi_index_container recursive
                                     |  modify
-------------------------------------+-------------------------------------

Comment (by Valentyn Shtronda <valiko.ua@…>):

 > ''`mod(e)` does not invoke any operation of the `multi_index_container`
 except possibly only before `e` is directly modified, and only as long as
 `position` is not rendered invalid.''
 Not very clear. I had to re-read it several times and think for some time
 to get it. It's very conservative and I understand you. But multi_index is
 more powerful than allowed by this statement (it's ok to call find on
 unaffected indices, it's ok to use trick with re-indexing), at least at
 the moment :)

 The problem was caused by modification of '''key fields''' of '''more than
 one element''' (and thus made their position invalid) before container got
 chance to re-position the latest one, and this may be done incorrectly.

 So I would re-state it somehow more straightforward. How about this draft:

 ''Modification of key fields in `e` makes corresponding indices
 temporarily broken, until `modify()` returns. If you need to restore them
 sooner than `modify()` returns (for example, for recursive calls to
 `modify()`) wrap modification of key fields in its own call to `modify()`.

 And/or give a link to some example where you could provide more verbose
 explanation of the problem and solution.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/11801#comment:9>
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