Re: [Boost-bugs] [Boost C++ Libraries] #10853: problem with detection of const_cast_from

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #10853: problem with detection of const_cast_from
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2014-12-07 23:37:45

#10853: problem with detection of const_cast_from
  Reporter: Matei David <matei@…> | Owner: igaztanaga
      Type: Bugs | Status: new
 Milestone: To Be Determined | Component: intrusive
   Version: Boost 1.57.0 | Severity: Problem
Resolution: | Keywords:

Comment (by Matei David <matei@…>):

 The non-template conversion function I was using (in 5 above) could do
 `Ptr<A>` to `Ptr<A>` conversion by using an intermediate `Ptr<const A>`
 object. The problem was not with the conversion function not being general
 enough, but with the `pointer_traits` code failing while detecting the
 presence of `const_cast_from`, because it involved an extra constructor
 call. This extra constructor call confused the overload resolution.

 I don't mind `const_cast_from` being a template, what I minded was finding
 it out the hard way. Perhaps this could be better explained here:

 Here's a suggestion:

 When defining a custom family of pointers or references to be used with BI
 library, make sure the public static conversion functions accessed through
 the `pointer_traits` interface (`*_cast_from` and `pointer_to`) can
 properly convert between const and nonconst referred member types
 __without the use of implicit constructor calls__. It is suggested these
 conversions be implemented as function templates, where the template
 argument is the type of the object being converted from.

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