Some user header files may define an abs macro which will cause a

syntax error if the #define happens before stdlib.h is included.
If abs is #defined, #undef and issue a warning.  This is similar
to what Tru64 UNIX does and is effectively the same as what happens
on Solaris (though on Solaris the real abs() is a macro).

src/include/stdlib.h

@@ -1,4 +1,4 @@
-/*	$OpenBSD: stdlib.h,v 1.17 2002/02/17 19:42:21 millert Exp $	*/
+/*	$OpenBSD: stdlib.h,v 1.18 2002/02/20 18:11:04 millert Exp $	*/
 /*	$NetBSD: stdlib.h,v 1.25 1995/12/27 21:19:08 jtc Exp $	*/
 
 /*-
@@ -92,6 +92,15 @@ typedef struct {
 
 #include <sys/cdefs.h>
 
+/*
+ * Some header files may define an abs macro.
+ * If defined, undef it to prevent a syntax error and issue a warning.
+ */
+#ifdef abs
+#undef abs
+#warning abs macro collides with abs() prototype, undefining
+#endif
+
 __BEGIN_DECLS
 __dead void	 abort(void);
 int	 abs(int);
@@ -116,8 +125,12 @@ void	*realloc(void *, size_t);
 void	 srand(unsigned);
 double	 strtod(const char *, char **);
 long	 strtol(const char *, char **, int);
+long long
+	 strtoll(const char *, char **, int);
 unsigned long
 	 strtoul(const char *, char **, int);
+unsigned long long
+	 strtoull(const char *, char **, int);
 int	 system(const char *);
 
 /* these are currently just stubs */
@@ -156,6 +169,8 @@ char	*l64a(long);
 
 void	 cfree(void *);
 
+#ifndef _GETOPT_DEFINED_
+#define _GETOPT_DEFINED_
 int	 getopt(int, char * const *, const char *);
 extern	 char *optarg;			/* getopt(3) external variables */
 extern	 int opterr;
@@ -164,6 +179,7 @@ extern	 int optopt;
 extern	 int optreset;
 int	 getsubopt(char **, char * const *, char **);
 extern	 char *suboptarg;		/* getsubopt(3) external variable */
+#endif /* _GETOPT_DEFINED_ */
 
 int	 heapsort(void *, size_t, size_t, int (*)(const void *, const void *));
 int	 mergesort(void *, size_t, size_t, int (*)(const void *, const void *));