#pragma 定义行为控制 defined behavior control - Serbipunk/notes GitHub Wiki
https://en.cppreference.com/w/cpp/preprocessor/impl https://zh.cppreference.com/w/cpp/preprocessor/impl
语法
#pragma 语用形参 (1)
_Pragma ( 字符串字面量 ) (2) (C++11 起)
Pragma directive controls implementation-specific behavior of the compiler,
such as disabling compiler warnings or changing alignment requirements.
Any pragma that is not recognized is ignored.
常见用例
#pragma once
#pragma back