Why is std::uint32_t different from uint32_t?

Question

I\'m a bit new to c++ and I have a coding assignment with a lot of files already done, but I noticed that VS2012 seems to have an issue with the following statement:

Answer 1

uint32_t (aka ::uint32_t i.e. the one in the global namespace) is declared in . That header might also declare it in namespace std, as std::uint32_t, but it's not required to do so.

std::uint32_t (i.e. the one in namespace std) is declared in . That header might also declare it in the global namespace, as ::uint32_t, but it's not required to do so.

If that's the case, why is this code acceptable outside of VS (ie. compiles properly using g++) but is unacceptable in VS? Can anyone please explain this?

If you want to use std::uint32_t then you must #include , or the code may not compile. If it does compile with G++ then presumably some other header indirectly includes but you shouldn't rely on that, include the right headers for the names you use.