#pragma once

#pragma once

Specifies that the file will be included (opened) only once by the compiler in a build. This can reduce build times as the compiler will not open and read the file after the first #include of the module.

指定当前文件在构建时只被包含(或打开)一次,这样就可以减少构建的时间,因为加入#pragma once后,编译器在打开或读取第一个#include 模块后,就不会再打开或读取随后出现的相同#include 模块.

For example,

// header.h
#pragma once