example static assert implemention

static_assert.c

#define static_assert(c) do { int _x = 1/((int)c); } while (0)

int main() {
    static_assert(sizeof(int) == 4);
    static_assert(sizeof(int) < 4);
    return 0;
}

/* output:
$ gcc t.c
t.c: In function ‘main’:
t.c:1:41: warning: division by zero [-Wdiv-by-zero]
    1 | #define static_assert(c) do { int _x = 1/((int)c); } while (0)
      |                                         ^
t.c:5:5: note: in expansion of macro ‘static_assert’
    5 |     static_assert(sizeof(int) < 4);
      |     ^~~~~~~~~~~~~
$
*/