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   Kelvin Chung  spake the secret code   
   <2011122621495936780-kelvSYC@maccom> thusly:   
      
   >I'm getting an unforseen problem when I'm trying to compile code for   
   >older compilers.  The following code compiles in clang 3.0 on a Mac:   
   >   
   >template    
   >struct Foo {   
   >	typedef Key& key_type;   
   >	   
   >	virtual Bar mapKey(const key_type& key) = 0;   
   >};   
   >   
   >However, when I compile with gcc 4.1.2 on SUSE Linux, I get "cannot   
   >declare reference to 'Key&', specifically wrt to mapKey().   
   >   
   >I'm trying to find the root cause of this: Is it a C++11-specifc thing,   
   >and thus barfing on gcc 4.1.2, which IIRC has no C++11 support?  Is it   
   >simply that I am expecting that "const key_type&" resolves to "Key&"   
   >(ie. the references "collapse"), when it shouldn't?  What should be the   
   >workaround for getting this snippet to compile under gcc 4.1.2?   
      
   You can't take a reference of a reference; this is not C++11 specific,   
   it has always been this way.   
      
   Look at Boost.TypeTraits for a way to identify if a type has a   
   reference and add one if it doesn't.   
      
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