From: marc.glisse@gmail.com   
      
   Marc  wrote:   
      
   > In C++, it is fairly common to pass functions an extra argument that   
   > is used purely for dispatching purposes (or at least type   
   > information), from a tag class that doesn't have any content.   
   [...]   
   > Now in all ABIs I have seen, since sizeof(Tag)==1, an object of size 1   
   > is copied, put on the stack (or in a register), etc, and nothing takes   
   > advantage of the fact that it could be implemented as a function with   
   > 1 fewer argument   
      
   I just found out that the "Itanium C++ ABI" (used by a large   
   proportion of C++ compilers) almost had this optimization thanks to   
   SGI, but then gcc and HP had some (unspecified) difficulty and it was   
   removed :-(   
      
   http://sourcery.mentor.com/public/cxx-abi/cxx-closed.html   
   issue A-5.   
      
   Obviously an ABI, like any standard, is a compromise that won't   
   satisfy everyone perfectly...   
      
      
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