AC_SYS_RESTARTABLE_SYSCALLS

[David Oleszkiewicz]

This is my first time using autoconf and i am a little confused with the
docs on this option.

The documentation states:

AC_SYS_RESTARTABLE_SYSCALLS
   If the system automatically restarts a system call that is interrupted
by a signal, define HAVE_RESTARTABLE_SYSCALLS.

the macro, so you needn't go find it is:

AC_DEFUN(AC_SYS_RESTARTABLE_SYSCALLS,
[AC_CACHE_CHECK(for restartable system calls,
ac_cv_sys_restartable_syscalls,
[AC_TRY_RUN(
[/* Exit 0 (true) if wait returns something other than -1,
   i.e. the pid of the child, which means that wait was restarted
   after getting the signal.  */
#include <sys/types.h>
#include <signal.h>
ucatch (isig) { }
main () {
  int i = fork (), status;
  if (i == 0) { sleep (3); kill (getppid (), SIGINT); sleep (3); exit (0);
}
  signal (SIGINT, ucatch);
  status = wait(&i);
  if (status == -1) wait(&i);
  exit (status == -1);
}
], ac_cv_sys_restartable_syscalls=yes,
ac_cv_sys_restartable_syscalls=no)])
if test $ac_cv_sys_restartable_syscalls = yes; then
  AC_DEFINE(HAVE_RESTARTABLE_SYSCALLS)
fi
])

which would seem to indicate that if the system automatically does not
restart system calls but rather wait() returns -1 (and presumably sets
errno to ERESTARTSYS or EINTR) the test would exit successfully meaning
no_default_restartable_syscall.
This result having no indication of whether the system is _able_ to
support automatically restarting system calls.

what am i missing.

thanks
dave