问题
If I use #define _POSIX_SOURCE in C so then what advantage do i get in my program. Can I access more libraries in my program or I can call some functions which are present directly in C. I mean what does this mysterious macros means after all?
回答1:
It allows you to use function that are not part of the standard C library but are part of the POSIX.1 (IEEE Standard 1003.1) standard. Using the macros described in feature_test_macros allows you to control the definitions exposed by the system header files.
As far as I know _POSIX_SOURCE is obsolete and you should use _POSIX_C_SOURCE instead.
For example, if you want to use strndup, you have to use
#define _POSIX_C_SOURCE 200809L
See also
- 1.3.4 Feature Test Macros
- 5.12 Posix Variants
- man 7 feature_test_macros
来源：https://stackoverflow.com/questions/48332332/what-does-define-posix-source-mean