Question

The C++ standards mentions that reinterpret_cast is implementation defined, and doesn’t give any guarantees except that casting back (using reinterpret_cast) to original type will result in original value passed to first.

C-style casting of at least some types behaves much the same way – casting back and forth results with the same value – Currently I am working with enumerations and ints, but there are some other examples as well.

While C++ standard gives those definitions for both cast-styles, does it also give the same guarantee for mixed casts? If library X returns from function int Y() some enum value, can use any of above casts, without worrying what cast was used to convert initial enum to int in Y’s body? I don’t have X’s source code, so I cannot check (and it can change with next version anyway), and things like that are hardly mentioned in documentation.

I know that under most implementations in such cases both casts behave the same; my question is: what does C++ standard say about such cases – if anything at all.

Answer 1

C++ defines the semantic of the C cast syntax in terms of static_cast, const_cast and reinterpret_cast. So you get the same guaranteed for the same operation whatever syntax you use to achieve it.