scc

 1#define TOLOWER(c) ((((unsigned)c) - 'A' < 26) ? ((c) | 32) : (c))
 2
 3int
 4main(void)
 5{
 6	char c, *s = "Bla";
 7
 8	c = TOLOWER((unsigned char)*s);
 9	if (c != 'b')
10		return 1;
11
12	return 0;
13}