c46ecbd2   
   From: daniel.kruegler@googlemail.com   
      
   Am 06.09.2011 00:19, schrieb Iker Jamardo Zugaza:   
   > I understand that the runtime cannot solve the   
   > problem but, Ulrich, sorry   
   >   
   >>   SPFooInherited pfi;   
   >>   SPFoo&  pf = pfi;   
   >>   
   >> This of course doesn't compile, because the two are not related.   
   >   
   > This code compiles perfectly.   
      
   This is probably a compiler defect or some "extension mode" (Do you use   
   a Visual Studio compiler?). It seems that the compiler allows binding a   
   temporary to a reference to non-const, which is illegal in standard C++.   
      
   > While creating the new pf reference, the   
   > smart pointer to Foo is able to check that the conversion from   
   > FooInherited is completely valid:   
   >   
   > FooInherited* fi;   
   > Foo* pf = fi;   
   >   
   > This is what is done internally in the shared_ptr class (more or less   
   > with some reference counter handling and such ;)).   
      
   This is a different story: The shared_ptr implementations typically   
   provide a constructor template that accepts pointers of derived types.   
   But the invocation of such a constructor is a conversion and in the   
   example code discussed this would have the effect to create a temporary   
   and bind it to an lvalue-reference to non-const, which is non-conforming.   
      
   > My assumption here is then that the runtime uses a different approach   
   > for calling functions and for catching exceptions even though it could   
   > look like the same at first sight.   
      
   Smart pointer constructions are different from real inheritance   
   relations. The exception machinery depends on real inheritance relations.   
      
   HTH & Greetings from Bremen,   
      
   Daniel Krügler   
      
      
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