+#define TOUPPER(c) _sch_toupper[(c) & 0xff]
+#define TOLOWER(c) _sch_tolower[(c) & 0xff]
+
+/* Prevent the users of safe-ctype.h from accidently using the routines
+ from ctype.h. Initially, the approach was to produce an error when
+ detecting that ctype.h has been included. But this was causing
+ trouble as ctype.h might get indirectly included as a result of
+ including another system header (for instance gnulib's stdint.h).
+ So we include ctype.h here and then immediately redefine its macros. */
+
+#include <ctype.h>
+#undef isalpha
+#define isalpha(c) do_not_use_isalpha_with_safe_ctype
+#undef isalnum
+#define isalnum(c) do_not_use_isalnum_with_safe_ctype
+#undef iscntrl
+#define iscntrl(c) do_not_use_iscntrl_with_safe_ctype
+#undef isdigit
+#define isdigit(c) do_not_use_isdigit_with_safe_ctype
+#undef isgraph
+#define isgraph(c) do_not_use_isgraph_with_safe_ctype
+#undef islower
+#define islower(c) do_not_use_islower_with_safe_ctype
+#undef isprint
+#define isprint(c) do_not_use_isprint_with_safe_ctype
+#undef ispunct
+#define ispunct(c) do_not_use_ispunct_with_safe_ctype
+#undef isspace
+#define isspace(c) do_not_use_isspace_with_safe_ctype
+#undef isupper
+#define isupper(c) do_not_use_isupper_with_safe_ctype
+#undef isxdigit
+#define isxdigit(c) do_not_use_isxdigit_with_safe_ctype
+#undef toupper
+#define toupper(c) do_not_use_toupper_with_safe_ctype
+#undef tolower
+#define tolower(c) do_not_use_tolower_with_safe_ctype