// Clause: 7.30.1 — The argument to iswalpha etc must be representable as wchar_t or equal to WEOF; otherwise UB.
#include <wctype.h>
#include <stdio.h>
int main(void){
    wint_t bad = (wint_t)-2; // not WEOF
    int r = iswalpha(bad); // UB
    printf("%d\n", r);
    return 0;
}