[Boost-bugs] [Boost C++ Libraries] #2649: iterator_range's assignment fires an assert when rhs is singular

Subject: [Boost-bugs] [Boost C++ Libraries] #2649: iterator_range's assignment fires an assert when rhs is singular
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2009-01-11 21:41:52

#2649: iterator_range's assignment fires an assert when rhs is singular
--------------------------------------+-------------------------------------
 Reporter:  eyal.farago_at_[hidden]  |       Owner:  doug_gregor
     Type:  Bugs                      |      Status:  new        
Milestone:  Boost 1.38.0              |   Component:  range      
  Version:  Boost 1.36.0              |    Severity:  Regression 
 Keywords:  iterator_range            |  
--------------------------------------+-------------------------------------
 the following code will raise an assertion in debug builds:


 {{{
 typedef boost::iterator_range<std::string> str_range_t;

 std::string eyal("eyal");
 str_range_t eyal_range( eyal ), empty_range;

 //here it is...
 eyal_range = empty_range;
 }}}


 the reason for the assert is an assert in iterator_range's begin/end
 methods, the assignment operator is doing something like
 {{{
 this->m_begin = rhs.begin()
 }}}
 which fails for debug builds when rhs is singular.

 a lot has been said about the decision to remove the singular
 member/concept from the library code, but I believe that assigning a
 singular range '''should not''' raise an assert.

 ps. I stumbled upon this bug after upgrading from 1.34 to 1.36, "I think
 this is a really nasty one because: [[BR]]
 1. it denies me from using a very standard use case.[[BR]]
 2. it simply crashes in release builds.[[BR]]
 3. a massive behavior change for singular ranges which used to behave like
 empty ranges. while I agree that using iterators of a singular range is a
 bad idea, querying for its length is not.[[BR]]

 eyal.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/2649>
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