Problem with __USE_XOPEN

[Keisuke Nishida]

The resent change in posix.c, which defines __USE_XOPEN, causes
the following error on my machine (RH7.0 + gcc-2.96 + glibc-2.2)

gcc -DHAVE_CONFIG_H -I.. -I./.. -I../libltdl -g -O2 -Wall -Wmissing-prototypes 
-Wp,-MD,.deps/posix.pp -c posix.c  -fPIC -DPIC -o .libs/posix.lo
In file included from posix.c:95:
/usr/include/sys/wait.h:113: parse error before `__stat_loc'
/usr/include/sys/wait.h:114: parse error before `__stat_loc'
In file included from posix.c:95:
/usr/include/sys/wait.h:161: parse error before `__stat_loc'
/usr/include/sys/wait.h:171: parse error before `__WAIT_STATUS'
posix.c: In function `scm_status_term_sig':
posix.c:503: warning: implicit declaration of function `WIFSIGNALED'
posix.c:504: warning: implicit declaration of function `WTERMSIG'
posix.c: In function `scm_status_stop_sig':
posix.c:521: warning: implicit declaration of function `WIFSTOPPED'
posix.c:522: warning: implicit declaration of function `WSTOPSIG'
posix.c: In function `scm_cuserid':
posix.c:1346: warning: implicit declaration of function `cuserid'
posix.c:1346: warning: assignment makes pointer from integer without a cast
make: *** [posix.lo] Error 1

I can avoid this error by removing the following line

  /* GNU/Linux libc requires __USE_XOPEN or cuserid() is not defined.  */
  #define __USE_XOPEN

and adding the following instead:

  extern char *cuserid (char *);

What would be the best solution?

Kei