什么是__pragma，__ pragma和#pragma有什么区别 [英] What is __pragma and what are the differences between __pragma and #pragma

问题描述

以下宏使我感到困惑.我想知道__pragma是什么，__ pragma和#pragma之间有什么区别.

The following macros confused me. I wondering what is __pragma and wwhat are the differences between __pragma and #pragma.

#define OPENVDB_START_THREADSAFE_STATIC_WRITE       __pragma(warning(disable:1711))
#define OPENVDB_FINISH_THREADSAFE_STATIC_WRITE      __pragma(warning(default:1711))

推荐答案

#pragma本身就是预处理器指令；它不能在#define指令中使用.

#pragma is a preprocessor directive in its own right; it can't be used within a #define directive.

因此，这就是__pragma存在的原因:它提供了一种方法，可以从使用它的宏扩展到的任何地方发出杂音.

So, this is why __pragma exists: it provides a way for a pragma to be issued from wherever the macro that uses it is expanded.

这是一个非标准的编译器扩展(MSVC，Intel和某些C编译器在不同程度上支持它).另请参见在较新版本的C/C ++标准中定义的 _Pragma运算符(具有相同的目的，但语法略有不同.

This is a non-standard compiler extension (MSVC, Intel, and some C compilers support it to varying degrees). See also the _Pragma operator that is defined in newer versions of the C/C++ standards (and serves the same purpose, but with a slightly different syntax).

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