如何强制printf在c中返回负值？

Question

I need to write a C program in which printf should return a negative value. It should be something like this:

#include <stdio.h>
int main()
{
    int ret_val;
    ret_val = printf(something);
    printf("%d", ret_val);
}

The output of this should be a negative number(ret_val should be negative).

Answer 1

Invoke an encoding error:

int ret = 0;
ret = printf("%lc", (wint_t) -1);
printf("%d\n", ret);

Answer 2

Redirect stdout to an invalid handle before doing your printf . For example, reopen it in read-only mode

freopen("fff", "r", stdout);