reinterpret_cast casts away qualifiers

Question

I add an issue on reinterpreting a variable and I don\'t know why..

int ProgressBar(const uint64_t data_sent, const uint64         


        

Answer 1

You need to also use a const_cast to remove const qualifiers. Also, casting from void * can use static_cast, it does not need to reinterpret. For example:

Dialog const *dialog = static_cast<Dialog const *>(data);
Dialog *d2 = const_cast<Dialog *>(dialog);

However , make sure that the Dialog is actually not a const object; attempting to modify a const object (presumably setValue does this) causes undefined behaviour.

I'd suggest rethinking the interface to ProgressBar to avoid needing this cast.

Answer 2

As Nick Strupat stated in comment,

reinterpret_cast can't cast away cv-qualifiers

So you can use reinterpret_cast and const_cast together.

Dialog *dialog = const_cast<Dialog*>(reinterpret_cast<const Dialog *>(data));