Question

I’ve got an unsigned and would like to convert that to an uint64_t (and back if possible).

How do I do that? If possible, I would like to avoid depending on undefined behaviour.

Thanks!

Answer 1

For instance:

const uint64_t bigvalue = (uint64_t) 42u;

Not sure if the cast is even necessary, since this doesn’t loose information. The opposite:

const unsigned int smallvalue = (unsigned int) bigvalue;

will need the cast, since it’s (probably, assuming int < uint64_t) a more narrow type.

Note: I mean “need” in a weak sense; since there is a risk of losing information when converting to a more narrow type, it’s likely that compilers will warn. The cast adds a sense of “I know what I’m doing” which is how such warnings are typically silenced.