Question

How can I remove all const qualifiers from a data type?

I tried to use std::remove_cv but it didnt work.

std::remove_cv< const char *>::type

Isn’t it the same as std::remove_cv<char*>::type?

Thanks.

Answer 1

The trait is doing everything correctly:

const char* is the same as char const* and neither is the same as char* const. So in your case, it’s the pointee that’s const, not the pointer. And remove_const (somewhat logically) only removes the outer const, not inner ones.

If you really want to remove the constness of the pointee, you can do it like this:

using T = char const*;
using NoConstT = std::add_pointer<std::remove_cv<std::remove_pointer<T>::type>::type>::type;

(Although std::add_pointer<T>::type could be dropped in favour of the simpler T* …)

That is: remove the pointer, remove the const of the pointee, make the result a pointer again.

In fact, this is a good opportunity to use use R. Martinho Fernandes’ excellent Wheels library which provides convenient shortcuts for such nested traits:

#include <wheels/meta.h++>
using namespace wheels;
…

using NoConstT = AddPointer<RemoveCv<RemovePointer<T>>>;

Much more readable.