Does const_cast ever cause actual code emission?

Question

Is it true that const_cast is just a way to tell the compiler "stop moaning, treat this as a non-const pointer"? Are there any cases when const_cast itself is translated into actual machine code?

Answer 1

Conceivably,there could be architectures where a const pointer had a different representation to a non-const one, in which case the compiler would have to emit some code. I'm not aware of any such architectures, however.

Answer 2

No, it just removes const attribute at compile time.

Answer 3

const_cast just throws away the constness of an attribute and nothing more.

Answer 4

const does not change the representation of a type, in particular, the representation of T* is exactly the same as T const*.

Consider:

int i, 
    * const cpi = &i,
    * const * pcpi = &cpi;
int const * const * pcpci = pcpi; // cpi is now int const*

The representation of cpi at the same time represents an int* and a int const* via *pcpci.

There is no way for the representation of cpi to change when pcpci is initialised.

Of course, if the pointer objects have non-significant bits, the compiler can flip them randomly; in particular, const_cast can flip the non-significant bits of a pointer, but any implicit conversion could also. I don't think this case exists in the real world.

The same apply when two different bit patterns result in the same address value (base+offset when offset is big enough).