Dealing with ctype.h integer overflow

Question

What is the proper way to deal with character values which when casted to an unsigned char fall between {INT_MAX + 1 ... UCHAR_MAX} where UCHAR_MAX is greater than INT_MAX.

int is_digit(char c) {
    unsigned char uchar = c;
    if(uchar > INT_MAX)
        return MAYBE;
    return isdigit((int)uchar) ? YES : NO;
}

Answer 1

The Unicode character set (which is the largest commonly used) has character codes from 0 to 0x10ffff. So, the only possiblity for a character code to be larger than INT_MAX is if int is a 16 bit type (or specifically less than 22 bits). If that would be the case, then you simply can not store a character code in an int.

If int is a 32 bit type (or at least 22 bits) then a character code will not overflow when cast to an int.