Re: [Boost-bugs] [Boost C++ Libraries] #5473: [Foreach] non-const rvalue collections are treated as const collections

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #5473: [Foreach] non-const rvalue collections are treated as const collections
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2011-04-15 01:13:52

#5473: [Foreach] non-const rvalue collections are treated as const collections
--------------------------------------+-------------------------------------
  Reporter:  mimomorin@…              |       Owner:  eric_niebler
      Type:  Patches                  |      Status:  new         
 Milestone:  To Be Determined         |   Component:  foreach     
   Version:  Boost Development Trunk  |    Severity:  Problem     
Resolution:                           |    Keywords:              
--------------------------------------+-------------------------------------

Comment (by mimomorin@…):

 Still fail to attach a patch for `foreach.hpp`...

 The patch (will be attached) does the following:

 1. Renaming functions
 * `is_const_` --> `is_nonconst_lvalue_`
   * Its return value is also changed.
 * `is_rvalue_` --> `is_nonconst_rvalue_`
   * The name of recently added `is_rvalue_(T&&, ...)` is not changed
     because it does detect the rvalueness
     (the ellipsis parameter is no longer needed and was removed).

 2. Introducing a new macro
 * BOOST_FOREACH_IS_CONST
   * This macro returns "true" if the collection is a const lvalue/rvalue.

 3. Hacking codes for BOOST_FOREACH_RUN_TIME_CONST_RVALUE_DETECTION
   (this might be an ugly hack...)
 * simple_variant
   * To deal with non-const rvalues, non-const `get` member function is
     added. This function returns non-const pointer to the (copied)
 collection.
   * Non-const lvalue collections are detected at compile-time, and so
     the non-const `get` function is only invoked for rvalues collections.
 * `begin`/`end`, `rbegin`/`rend`
   * These functions are modified to accept non-const collections.
   * Constness of the collection is propagated by means of `auto_any_cast`.
     If the collection is const, `auto_any_cast` returns const
 `simple_variant`
     reference. Otherwise, it returns non-const `simple_variant` reference.


 All the tests (+ `mutate_rvalue.cpp`) ran successfully with the following
 compilers (both in C++03 and C++0x modes):
 gcc-4.3.5, gcc-4.4.5, gcc-4.5.2, gcc-4.6.0, clang (TOT).

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/5473#comment:2>
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