什么是-D_XOPEN_SOURCE做/是什么意思? [英] What does -D_XOPEN_SOURCE do/mean?
问题描述
我最近遇到了一些code的GCC没有这个ARG不会编译。我检查了海湾合作委员会手册页,却没有发现这个特定的选项。我没有找到 XOPEN_SOURCE
,但有什么它做一点解释。
I recently encountered some code that gcc would not compile without this arg. I checked the gcc man page, but did not find this specific option. I did find XOPEN_SOURCE
, but there was little explanation of what it does.
可有人请详细点吗?我知道 -D_XOPEN_SOURCE
可设置为不同的值,例如 400
, 600
,但什么做那些呢?
Can someone please elaborate? I know -D_XOPEN_SOURCE
can be set to different values, such 400
, 600
, but what do those do?
推荐答案
当你做
#define _XOPEN_SOURCE <some number>
或
cc -D_XOPEN_SOURCE=<some number>
它会告诉你的编译器包含在X / Open和POSIX标准中定义的一些额外的功能定义。
it tells your compiler to include definitions for some extra functions that are defined in the X/Open and POSIX standards.
这会给你存在于最新的UNIX / BSD / Linux系统,但可能在其他系统如Windows不存在一些额外的功能。
This will give you some extra functionality that exists on most recent UNIX/BSD/Linux systems, but probably doesn't exist on other systems such as Windows.
中的数字代表不同版本的标准
The numbers refer to different versions of the standard.
- 500 - 在X / Open 5,1995年纳入POSIX
- 600 - 在X / Open 6,2004年纳入POSIX
- 700 - 在X / Open 7,结合POSIX 2008
- 500 - X/Open 5, incorporating POSIX 1995
- 600 - X/Open 6, incorporating POSIX 2004
- 700 - X/Open 7, incorporating POSIX 2008
您可以告诉你需要哪一个(如果有的话)通过查看每次调用函数的手册页。
You can tell which one you need (if any) by looking at the man page for each function you call.
例如,的strdup人
说:
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
strdup(): _SVID_SOURCE || _BSD_SOURCE || _XOPEN_SOURCE >= 500
strndup(), strdupa(), strndupa(): _GNU_SOURCE
这意味着你应该把其中的一个:
Which means that you should put one of these:
#define _SVID_SOURCE
#define _BSD_SOURCE
#define _XOPEN_SOURCE 500
#define _XOPEN_SOURCE 600
#define _XOPEN_SOURCE 700
在源文件中做任何的#include
■如果您想使用前顶部的strdup
。
at the top of your source file before doing any #include
s if you want to use strdup
.
或者你可以把
#define _GNU_SOURCE
有相反,它使所有的功能,与它可能无法在Solaris,FreeBSD的,Mac OS X中,编译等缺点。
there instead, which enables all functionality, with the downside that it might not compile on Solaris, FreeBSD, Mac OS X, etc.
这是一个好主意,做一个的#include
,的#define
,或使用前要检查每一个人页面新的功能,因为有时候他们的行为改变取决于哪些选项和的#define
你得了,例如使用的基本名(3)。
It's a good idea to check each man page before doing a #include
, #define
, or using a new function, because sometimes their behavior changes depending on what options and #define
s you have, for example with basename(3).
另请参阅:
- -std=c99 wtf on Linux
- glibc feature test macros
- The Compilation Environment - Open Group Base Specification issue 6 (a.k.a. X/Open 6)
- POSIX - Wikipedia
- Single UNIX Specification - Wikipedia
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