[Boost-bugs] [Boost C++ Libraries] #4337: info.hpp: unnecessary (?) temporary shared_ptr<error_info_base const>

Subject: [Boost-bugs] [Boost C++ Libraries] #4337: info.hpp: unnecessary (?) temporary shared_ptr<error_info_base const>
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2010-06-13 01:02:36

#4337: info.hpp: unnecessary (?) temporary shared_ptr<error_info_base const>
--------------------------+-------------------------------------------------
 Reporter:  niels_dekker  |       Owner:  emildotchevski
     Type:  Bugs          |      Status:  new           
Milestone:  Boost 1.43.0  |   Component:  exception     
  Version:  Boost 1.44.0  |    Severity:  Optimization  
 Keywords:                |  
--------------------------+-------------------------------------------------
 It seems to me that the creation of a temporary shared_ptr<error_info_base
 const> object at
 [https://svn.boost.org/trac/boost/browser/trunk/boost/exception/info.hpp?rev=61602#L117

 info.hpp line 117] is unnecessary:

 {{{
   shared_ptr<error_info_base const> const & x = i->second;
 }}}

 In the quoted code above, a temporary copy of i->second must be created,
 because i->second itself is a non-const shared_ptr<error_info_base>. It
 seems to me that this temporary copy can be avoided easily by removing the
 inner const from the type of x:
 {{{
   shared_ptr<error_info_base> const & x = i->second;
 }}}

 Or by declaring x as a raw pointer:
 {{{
   error_info_base const * const x = i->second.get();
 }}}

 What do you think?

 FYI, this line of code drew my attention, because of a Codegear warning:
 {{{
 Warning W8028 ..\..\..\boost/exception/info.hpp 117: Temporary used to
 initialize 'x' in function
 error_info_container_impl::diagnostic_information(const char *) const
 }}}
 Each of the two suggested changes would fix the warning.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/4337>
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