with macros 1.17.0 and gcc

make  all-recursive
make[1]: Entering directory `/home/sarvatt/source/luit'
Making all in man
make[2]: Entering directory `/home/sarvatt/source/luit/man'
  GEN    luit.1
make[2]: Leaving directory `/home/sarvatt/source/luit/man'
make[2]: Entering directory `/home/sarvatt/source/luit'
  CC     charset.o
  CC     iso2022.o
  CC     locale.o
  CC     luit.o
  CC     other.o
  CC     parser.o
  CC     sys.o
sys.c: In function ‘allocatePty’:
sys.c:339:5: warning: implicit declaration of function ‘posix_openpt’ [-Wimplicit-function-declaration]
sys.c:339:5: warning: nested extern declaration of ‘posix_openpt’ [-Wnested-externs]
  CCLD   luit
make[2]: Leaving directory `/home/sarvatt/source/luit'
make[1]: Leaving directory `/home/sarvatt/source/luit'

With macros 1.15.0 where it succeeds

make  all-recursive
make[1]: Entering directory `/home/tinderbox/xorg/app/luit'
Making all in man
make[2]: Entering directory `/home/tinderbox/xorg/app/luit/man'
  GEN    luit.1
make[2]: Leaving directory `/home/tinderbox/xorg/app/luit/man'
make[2]: Entering directory `/home/tinderbox/xorg/app/luit'
  CC     charset.o
  CC     iso2022.o
  CC     locale.o
  CC     luit.o
  CC     other.o
  CC     parser.o
  CC     sys.o
sys.c: In function 'allocatePty':
sys.c:339: warning: implicit declaration of function 'posix_openpt'
sys.c:339: warning: nested extern declaration of 'posix_openpt'
  CCLD   luit
make[2]: Leaving directory `/home/tinderbox/xorg/app/luit'
make[1]: Leaving directory `/home/tinderbox/xorg/app/luit'


with this is the build succeeds with gcc

diff --git a/sys.c b/sys.c
index 8463b05..5bf0491 100644
--- a/sys.c
+++ b/sys.c
@@ -20,6 +20,8 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 */
 
+#define _XOPEN_SOURCE 600
+
 #ifdef HAVE_CONFIG_H
 # include "config.h"
 #endif

also passing --disable-selective-werror to configure with util-macros 1.16.1+ succeeds. Is there any way this -Werror stuff in util-macros can be opt-in instead of opt-out by default? Is breaking previous tarball releases with macro updates the way to go? macros being backwards compatible was seemingly implicit in the past, breaking older releases seems strange to me and will mean the linux distro I use can't backport it so people can build new driver releases without building macros themselves anymore.