pragma once - Wikipedia

The correct title of this article is #pragma once. The omission of the # is due to technical restrictions. In the C and C++ programming languages, #pragma once is a non-standard but widely supported preprocessor directive designed to cause the current header file to be included only once in a single compilation.[1] Thus, #pragma once serves the same purpose as include guards, but with several adva

[naka-06_18]

Clang / GCC 3.4~ / VC でサポート

[taroleo]

include guardに#pragma onceが正式に使えるようになったのはGCC3.4から

[hikobae]

portable なコードを書くには、include guards と #pragma once を併用すること