--- ray/src/util/rpiece.c	2004/06/08 19:48:31	2.44
+++ ray/src/util/rpiece.c	2007/08/22 17:49:54	2.46
@@ -1,5 +1,5 @@
 #ifndef lint
-static const char	RCSid[] = "$Id: rpiece.c,v 2.44 2004/06/08 19:48:31 greg Exp $";
+static const char	RCSid[] = "$Id: rpiece.c,v 2.46 2007/08/22 17:49:54 greg Exp $";
 #endif
 /*
  * Generate sections of a picture.
@@ -9,7 +9,9 @@ static const char	RCSid[] = "$Id: rpiece.c,v 2.44 2004
 #include <stdio.h>
 #include <signal.h>
 #include <sys/types.h>
-#include <sys/wait.h>
+#ifndef NON_POSIX /* XXX need abstraction for process management */
+ #include <sys/wait.h>
+#endif
 
 #include "platform.h"
 #include "standard.h"
@@ -246,6 +248,10 @@ init(			/* set up output file and start rpict */
 					/* compute piece size */
 	hres /= hmult;
 	vres /= vmult;
+	if (hres <= 0 || vres <= 0) {
+		fprintf(stderr, "%s: illegal resolution/subdivision\n");
+		exit(1);
+	}
 	normaspect(viewaspect(&ourview)*hmult/vmult, &pixaspect, &hres, &vres);
 	sprintf(hrbuf, "%d", hres);
 	rpargv[rpargc++] = "-x"; rpargv[rpargc++] = hrbuf;