lib: don't check for dup3 support - it has been around a long time

dup3() was introduced in Linux 2.6.27 and glibc 2.9.

Signed-off-by: Quentin Armitage <[email protected]>

Author: pqarmitage

configure.ac

@@ -1380,8 +1380,7 @@ AC_FUNC_FORK
 # We add malloc and realloc to AC_CHECK_FUNCS instead.
 #AC_FUNC_MALLOC
 #AC_FUNC_REALLOC
-dnl - dup3 since Linux 2.6.27 and glibc 2.9
-AC_CHECK_FUNCS([dup2 dup3 getcwd gettimeofday malloc memmove memset realloc select setenv socket strcasecmp strchr strdup strerror strpbrk strstr strtol strtoul uname])
+AC_CHECK_FUNCS([getcwd gettimeofday malloc memmove memset realloc select setenv socket strcasecmp strchr strdup strerror strpbrk strstr strtol strtoul uname])
 dnl - vsyslog() Not defined by Posix, but available in glibc and musl
 AC_CHECK_FUNCS([vsyslog], [add_system_opt([VSYSLOG])])
 

lib/parser.c

@@ -3460,11 +3460,7 @@ separate_config_file(void)
 		log_message(LOG_INFO, "Failed to open %s for conf_copy", buf);
 		return;
 	}
-#ifdef HAVE_DUP3
+
 	dup3(fd, fd_orig, O_CLOEXEC);
-#else
-	dup2(fd, fd_orig);
-	fcntl(fd_orig, F_SETFD, fcntl(fd_orig, F_GETFD) | FD_CLOEXEC);
-#endif
 	close(fd);
 }