solaris에서 shm_open compile 에러..

조건부 컴파일문을 해석하면
1. _POSIX_C_SOURCE 와 _XOPEN_SOURCE 가 모두 정의안되어 있거나
2. __EXTENSIONS__ 가 정의되어 있거나
3. _XPG4_2가 정의되어 있는 경우

이기 때문에 2번이나 3번을 만족한다면
_POSIX_C_SOURCE와 _XOPEN_SOURCE 를 정의해도 전혀 문제가 안됩니다.

__EXTENSIONS__ 나 _XPG4_2 는 직접 정의하셔도 되겠지만,
다른 정의에 의해서 유도되기도 합니다.

Solaris 7의 /usr/include/sys/feature_tests.h 를 보시면

/*
 * UNIX 95 implementation
 *
 * As specified in the following X/Open specifications:
 *
 *   System Interfaces and Headers, Issue 4, Version 2
 *   Commands and Utilities, Issue 4, Version 2
 *   Networking Services, Issue 4
 *   X/Open Curses, Issue 4
 *
 * application writers wishing to use any functions specified
 * as X/Open UNIX Extension must define _XOPEN_SOURCE and
 * _XOPEN_SOURCE_EXTENDED=1.  The Sun internal macro _XPG4_2
 * should not be used in its place as unexpected results may
 * occur.
 */
#if (defined(_XOPEN_SOURCE) && _XOPEN_SOURCE_EXTENDED - 0 == 1)
#define _XPG4_2
#endif

/*
 * UNIX 98 implementation
 *
 * As specified in the following X/Open specfications:
 *
 *   System Interfaces and Headers, Issue 5
 *   Commands and Utilities, Issue 5
 *   Networking Services, Issue 5
 *   X/Open Curses, Issue 4, Version 2
 *
 * application writers wishing to utilize UNIX 98 functionality
 * must define _XOPEN_SOURCE=500.  This turns on UNIX 95 functionality
 * which is a subset of UNIX 98, and also turns on POSIX Realtime and
 * POSIX Threads functionality.
 */
#if (_XOPEN_SOURCE - 0 == 500)
#define _XPG5
#define _XPG4_2
#undef  _POSIX_C_SOURCE
#define _POSIX_C_SOURCE                 199506L
#define _POSIX_PTHREAD_SEMANTICS        1
#endif

와 같이 되어있어서 _XOPEN_SOURCE 가 500 이거나
_XOPEN_SOURCE_EXTENDED=1인 경우에는 _XPG4_2 가
정의되도록 되어있습니다.

Solaris 7과 8에서 아래 코드와 컴파일 옵션은 아무런 오류없이 컴파일되었습니다.

#include <unistd.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/mman.h>

int
main(int argc, char **argv)
{
        struct timeval  tv;

        shm_open(NULL, 0, 0);
}

#!/bin/sh -v

cc -D_POSIX_C_SOURCE=199506L -D_XOPEN_SOURCE -D_XOPEN_SOURCE_EXTENDED timeval_compile_error.c -lrt
cc -D__EXTENSIONS__ timeval_compile_error.c -lrt
cc -D_POSIX_C_SOURCE=199506L -D_XOPEN_SOURCE=500 timeval_compile_error.c -lrt
cc -D_POSIX_C_SOURCE=199506L -D_XOPEN_SOURCE=500 timeval_compile_error.c -lrt