uclibc-ng/docs/wchar_and_locale.txt

		User-configurable

UCLIBC_HAS_CTYPE_TABLES
	Make toupper etc work thru translation tables
	and isalhum etc thru lookup tables. Help says:
	"While the non-table versions are often smaller when building
	statically linked apps, they work only in stub locale mode."

	"stub locale mode" is when !UCLIBC_HAS_LOCALE I presume,
	when we are permanently in POSIX/C locale.

UCLIBC_HAS_CTYPE_SIGNED
	Handle sign-extended chars. I.e. if you want
	toupper((char)0xa0) => toupper(0xffffffa0) => still works correctly,
	as if toupper(0xa0) was called.

UCLIBC_HAS_CTYPE_UNSAFE/CHECKED/ENFORCED
	Do not check ctype function argument's range/check it and return
	error/check it and abort(). Help says:
	NOTE: This only affects the 'ctype' _functions_.  It does not affect
	the macro implementations. [so what happens to macros?]
	[examples?]

UCLIBC_HAS_WCHAR
	Wide character support. I assume all those wchar_t types and functions

UCLIBC_HAS_LOCALE/XLOCALE
	Support locale / extended locale

UCLIBC_PREGENERATED_LOCALE_DATA
	Not recommended


		uclibc internal machinery

__LOCALE_C_ONLY
	#defined if !UCLIBC_HAS_LOCALE

__NO_CTYPE
	#defined only by some .c files. Prevents ctype macros to be #defined
	(those w/o underscores. __ctype() macros will still be defined).
	Looks like user is expected to never mess with defining it.

__UCLIBC_DO_XLOCALE
	#defined only by some .c files. Looks like user is expected to never
	mess with defining it.

__XL_NPP(N) - "add _l suffix if locale support is on"
	#defined to N ## _l if __UCLIBC_HAS_XLOCALE__ && __UCLIBC_DO_XLOCALE,
	else #defined to just N.

__CTYPE_HAS_8_BIT_LOCALES
__CTYPE_HAS_UTF_8_LOCALES
	Depends on contents of extra/locale/LOCALES data file. Looks like
	both will be set if UCLIBC_HAS_LOCALE and extra/locale/LOCALES
	is not edited.

__WCHAR_ENABLED
	locale_mmap.h defines it unconditionally, extra/locale/gen_ldc.c
	defines it too with a warning, and _then_ includes locale_mmap.h.
	Makefile seems to prevent the warning in gen_ldc.c:
	ifeq ($(UCLIBC_HAS_WCHAR),y)
	BUILD_CFLAGS-gen_wc8bit += -DDO_WIDE_CHAR=1
	BUILD_CFLAGS-gen_ldc += -D__WCHAR_ENABLED=1
	endif
	A mess. Why they can't just use __UCLIBC_HAS_WCHAR__?

__WCHAR_REPLACEMENT_CHAR
	Never defined (dead code???)



		Actual ctype macros are a bloody mess!

ctype.h
...
...
#define __isctype(c, type) \
  ((__UCLIBC_CTYPE_B)[(int) (c)] & (__ctype_mask_t) type)

#define __isascii(c)    (((c) & ~0x7f) == 0)    /* If C is a 7 bit value.  */
#define __toascii(c)    ((c) & 0x7f)            /* Mask off high bits.  */
#define __isdigit_char(C)    (((unsigned char)((C) - '0')) <= 9)
#define __isdigit_int(C)     (((unsigned int)((C) - '0')) <= 9)

# define isalnum(c)     __isctype((c), _ISalnum)
# define isalpha(c)     __isctype((c), _ISalpha)

# if __GNUC__ >= 2 && defined __OPTIMIZE__ && !defined __cplusplus
#  define tolower(c)    __tobody (c, tolower, __UCLIBC_CTYPE_TOLOWER, (c))
#  define toupper(c)    __tobody (c, toupper, __UCLIBC_CTYPE_TOUPPER, (c))
# endif /* Optimizing gcc */

# if defined __USE_SVID || defined __USE_MISC || defined __USE_XOPEN
#  define isascii(c)    __isascii (c)
#  define toascii(c)    __toascii (c)
#  define _tolower(c)   ((int) (__UCLIBC_CTYPE_TOLOWER)[(int) (c)])
#  define _toupper(c)   ((int) (__UCLIBC_CTYPE_TOUPPER)[(int) (c)])
# endif
...
...

bits/uClibc_ctype.h
...
...
#define __tolower(c)            __body(tolower,c)
#define __toupper(c)            __body(toupper,c)

#define _toupper(c) ((c) ^ 0x20)
#define _tolower(c) ((c) | 0x20)
...
...

WTF?! We have (at least) TWO DIFFERENT _tolower's?