19.8.2. reinterpret

19.8.2. `reinterpret_cast`
	19.8. Safer Typecasting Using ANSI C++ Typecasts

[ fromfile: types.xml id: reinterpretcast ]

reinterpret_cast is used for casts that are representation- or system-dependent.
e.g.,
- conversions between unrelated types such as int to pointer
- conversions between unrelated pointer types such as int* to double*
reinterpret_cast cannot cast away const.

reinterpret_casts are dangerous, generally not portable, and should be avoided.

        Spam spam;
        Egg* eggP;
        eggP = reinterpret_cast<Egg*>(&spam);
        eggP->scramble();

reinterpret_cast takes some spam and gives us an Egg-shaped pointer, without any concern for type-compatibility.
eggP is reinterpreting the bits of spam as if they were bits of egg.
In some countries, this would be sacrilege!

Sometimes, a C function returns a void* pointing to a type that is known to the developer.
In such a case, a typecast from void* to the actual type is needed.
If you are sure it is pointing to an Egg, reinterpret_cast<Egg*> is the appropriate cast to use.
There is no compiler or runtime checking on such a cast.

For example, we use reinterpret_cast on a void* in the QMetaType example, Example 12.15.


19.8.1.1. Exercises: static_cast and const_cast		19.8.3. Why Not Use C-Style Casts?