22e05073   
   From: brangdon@cix.compulink.co.uk   
      
   kmccarty@googlemail.com (Kevin McCarty) wrote (abridged):   
   > Of course a caller who was unaware of the reference return type   
   > might instead write   
   >   
   >      const Matrix4 & result = a + b + c;   
   >   
   > and end up with a dangling reference.  Is this where the trouble   
   > comes from in your opinion?   
      
   Yes.   
      
      
   > Is it just too unsafe to do this in real-world code, so that even   
   > in C++ 2011 we can take full advantage of modifying temporary   
   > objects only when their class type is built mainly from   
   > stuff allocated with new[]?   
      
   That sounds reasonable to me.   
      
   In practice, return value optimisations are often sufficient. In this   
   case we could probably write:   
      
       Matrix4 operator+( const Matrix4 &lhs, const Matrix4 &rhs ) {   
           Matrix4 result;   
           result._m[0] = lhs._m[0] + rhs._m[0];   
           // ...   
           return result;   
       }   
      
   and avoid redundant copying.   
      
   -- Dave Harris, Nottingham, UK.   
      
      
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