在C程序中应如何以及何时使用_POSIX_C_SOURCE? [英] How and when should I use _POSIX_C_SOURCE in C programs?

问题描述

我已经不得不维护一些C项目，该项目也应该在较旧的平台上进行编译.目前，对于某些平台，已定义宏_POSIX_C_SOURCE.我在想-定义它是否可以接受，我是否应该在所有平台上不总是定义它?也许具有最高的相关价值?

I've gotten myself into having to maintain some C project which should also compile on older platforms. At the moment, for some platforms, the macro _POSIX_C_SOURCE is defined. I was wondering - if it's acceptable to have it defined, should I not just define it always, on all platforms? And perhaps with the highest relevant value?

概括地说，我想问的是:_POSIX_C_SOURCE何时何地应在什么条件下使用?

To generalize, I suppose I'm asking: When and under what conditions should _POSIX_C_SOURCE be used?

推荐答案

_POSIX_C_SOURCE提供了不同的功能.

_POSIX_C_SOURCE 1使POSIX.1标准中的功能可用 _POSIX_C_SOURCE 2使POSIX.2标准中的功能可用 _POSIX_C_SOURCE 199309L使POSIX.1b标准中的功能可用

_POSIX_C_SOURCE 1 makes the functionality from the POSIX.1 standart available _POSIX_C_SOURCE 2 makes the functionality from the POSIX.2 standart available _POSIX_C_SOURCE 199309L makes the functionality from the POSIX.1b standart available

更高的值(如200809L)使更多功能可用. (第7人，feature_test_macros)

Higher values like 200809L make more features available. (man 7 feature_test_macros)

通常，如果您需要严格遵守POSIX，则需要_POSIX_C_SOURCE.

如果您不关心特定的POSIX标准合规性，则可以在每个项目中对其进行定义.

It is safe to define it in every project if you don't care for specific POSIX standard compliance.

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