// Clause: 7.30 — tow* functions same precondition as isw*; otherwise UB.
#include <wctype.h>
#include <wchar.h>
#include <stdio.h>
int main(void){
    wint_t bad = (wint_t)-3; // not WEOF
    wint_t r = towupper(bad); // UB
    printf("%d\n", (int)r);
    return 0;
}