NOI这么搞没问题吧

#include <stdio.h>
#include <complex.h>

// test complex
int main()
{
    // case 1 : c99
    double _Complex f = -1;
    f = csqrtf(f) + 0.1i;
    printf("The complex number is %g+%gi\n", creal(f), cimag(f));

    // case 2 : c11
    complex double c = -1;
    c = csqrtf(c) + 0.1i;
    printf("The complex number is %g+%gi\n", __real__(c), __imag__(c));
}