-#define ARG_MAX (256 * 1024) /* max bytes for an exec function */
-#define CHILD_MAX 100 /* max simultaneous processes */
-#define GID_MAX 2147483647U /* max value for a gid_t (2^31-2) */
-#define LINK_MAX 32767 /* max file link count */
-#define MAX_CANON 255 /* max bytes in term canon input line */
-#define MAX_INPUT 255 /* max bytes in terminal input */
-#define NAME_MAX 255 /* max bytes in a file name */
-#define NGROUPS_MAX 16 /* max supplemental group id's */
-#define UID_MAX 2147483647U /* max value for a uid_t (2^31-2) */
-#define OPEN_MAX 10240 /* max open files per process */
-#define PATH_MAX 1024 /* max bytes in pathname */
-#define PIPE_BUF 512 /* max bytes for atomic pipe writes */
+#define ARG_MAX (256 * 1024) /* max bytes for an exec function */
+#if !defined(_POSIX_C_SOURCE) || defined(_DARWIN_C_SOURCE)
+#define CHILD_MAX 266 /* max simultaneous processes */
+#define GID_MAX 2147483647U /* max value for a gid_t (2^31-2) */
+#endif /* (_POSIX_C_SOURCE && !_DARWIN_C_SOURCE) */
+#define LINK_MAX 32767 /* max file link count */
+#define MAX_CANON 1024 /* max bytes in term canon input line */
+#define MAX_INPUT 1024 /* max bytes in terminal input */
+#define NAME_MAX 255 /* max bytes in a file name */
+#define NGROUPS_MAX 16 /* max supplemental group id's */
+#if !defined(_POSIX_C_SOURCE) || defined(_DARWIN_C_SOURCE)
+#define UID_MAX 2147483647U /* max value for a uid_t (2^31-2) */
+
+#define OPEN_MAX 10240 /* max open files per process - todo, make a config option? */
+
+#endif /* (_POSIX_C_SOURCE && !_DARWIN_C_SOURCE) */
+#define PATH_MAX 1024 /* max bytes in pathname */
+#define PIPE_BUF 512 /* max bytes for atomic pipe writes */
+
+#define BC_BASE_MAX 99 /* max ibase/obase values in bc(1) */
+#define BC_DIM_MAX 2048 /* max array elements in bc(1) */
+#define BC_SCALE_MAX 99 /* max scale value in bc(1) */
+#define BC_STRING_MAX 1000 /* max const string length in bc(1) */
+#define CHARCLASS_NAME_MAX 14 /* max character class name size */
+#define COLL_WEIGHTS_MAX 2 /* max weights for order keyword */
+#define EQUIV_CLASS_MAX 2
+#define EXPR_NEST_MAX 32 /* max expressions nested in expr(1) */
+#define LINE_MAX 2048 /* max bytes in an input line */
+#define RE_DUP_MAX 255 /* max RE's in interval notation */