Add alternate implementation of waitpid() for systems that have wait4 but

not wait3, in particular Amdahl's SVR2-based UTS 2.1.2.  The code comes
from apache, but I contributed it to apache in the first place.

configure.in

@@ -49,7 +49,7 @@ fi
 
 AC_FUNC_MEMCMP
 AC_FUNC_UTIME_NULL
-AC_CHECK_FUNCS(waitpid getcwd strdup strerror chown chmod mknod)
+AC_CHECK_FUNCS(waitpid wait4 getcwd strdup strerror chown chmod mknod)
 AC_CHECK_FUNCS(fchmod fstat strchr readlink link utime utimes strftime)
 AC_CHECK_FUNCS(memmove getopt_long lchown vsnprintf snprintf setsid glob strpbrk)
 AC_CHECK_FUNCS(strlcat strlcpy)

lib/compat.c

@@ -46,7 +46,25 @@
 #ifndef HAVE_WAITPID
  pid_t waitpid(pid_t pid, int *statptr, int options)
 {
+#ifdef HAVE_WAIT4
 	return wait4(pid, statptr, options, NULL);
+#else
+	/* If wait4 is also not available, try wait3 for SVR3 variants */
+	/* Less ideal because can't actually request a specific pid */
+	/* At least the WNOHANG option is supported */
+	/* Code borrowed from apache fragment written by dwd@bell-labs.com */
+	int tmp_pid, dummystat;;
+	if (kill(pid, 0) == -1) {
+		errno = ECHILD;
+		return -1;
+	}
+	if (statptr == NULL)
+		statptr = &dummystat;
+	while (((tmp_pid = wait3(statptr, options, 0)) != pid) &&
+		    (tmp_pid != -1) && (tmp_pid != 0) && (pid != -1))
+	    ;
+	return tmp_pid;
+#endif
 }
 #endif