hextoint(int c)
{
	if (!isascii((unsigned char) c))
		return -1;
	if (isdigit((unsigned char) c))
		return c - '0';
	if ((c >= 'a') && (c <= 'f'))
		return c + 10 - 'a';
	if (( c>= 'A') && (c <= 'F'))
		return c + 10 - 'A';
	return -1;
}

Originally addressing errors in controlling program flow through indirect calls or jumps, this CWE has been deprecated and its concerns merged into more precise modern classifications.