[boost] Re: operators.hpp bugs

From: Daniel Frey (d.frey_at_[hidden])
Date: 2005-04-28 13:55:02

Søren Lassen wrote:
> The standard places some limits on when NAMED objects may be optimized  
> away. From this follows implicitly that UNNAMED objects may always be  
> optimized away. Or, to quote from Scott Meyers' "More Effective C++", 
> page  109-110: "However, the fact remains that unnamed objects have 

BTW, did you read Scott's errata? To quote from it:

109  Both the first and second implementations on this page
      suffer from the problem that they are returning whatever
      operator=+ returns.  In general, there is no way to know
      what this is (yes, it's a reference to an object of type T,
      but a reference to which T object?), hence no way for
      compilers to optimize away the copy to operator+'s return
      value.  The way to write operator+ such that the return
      value optimization can be performed is with this body:

        T result(lhs);
        result += rhs;
        return result.

taken from <http://www.aristeia.com/BookErrata/mec++-errata_frames.html>

Regards, Daniel