Versions

libc {
  GLIBC_2.0 {
    # global variables
    __ctype_b; __ctype32_b; __ctype_tolower; __ctype_toupper;
    _tolower; _toupper;

    # i*
    isalnum; isalpha; isascii; isblank; iscntrl; isdigit; isgraph; islower;
    isprint; ispunct; isspace; isupper; isxdigit;

    # t*
    toascii; tolower; toupper;
  }
  GLIBC_2.2 {
    # global variables
    __ctype32_tolower; __ctype32_toupper;
  }
  GLIBC_2.3 {
    isctype; __isctype;

    # functions used by optimized macros in ctype.h
    __ctype_b_loc; __ctype_tolower_loc; __ctype_toupper_loc;
  }
  GLIBC_PRIVATE {
    __ctype_init;
  }
}