Unless you're working on embedded hardware with proprietary compilers, #pragma once is supported by all compilers (see https://en.wikipedia.org/wiki/Pragma_once

Unless you're working on embedded hardware with proprietary compilers, #pragma once is supported by all compilers (see https://en.wikipedia.org/wiki/Pragma_once https://en.wikipedia.org/wiki/Pragma_once). You can safely assume it'll be available on your platform.