dangerous lack of lifetimes

lib.rs

#[no_mangle]
pub extern "C" fn det_c(m3x3: *const [[f64; 3]; 3]) -> f64 {
    let m1 = unsafe { &*m3x3 };
    ((m1[0][0] * (m1[1][1] * m1[2][2] - m1[2][1] * m1[1][2]))
        - (m1[0][1] * (m1[1][0] * m1[2][2] - m1[2][0] * m1[1][2]))
        + (m1[0][2] * (m1[1][0] * m1[2][1] - m1[2][0] * m1[1][1])))
}

main.c

#include <stdio.h>
#include <stdlib.h>

extern double det_c ( const double m1[3][3] );

int main() {
  double m1[3][3] = {1, 2, 3, 0,5,6, 0,0,9};

  printf("%f\n", det_c(m1));
  return 0;
}

Makefile

coffee:
	rustc lib.rs --crate-type=cdylib -C opt-level=3 -C target-cpu=native
	gcc main.c -o main.o -L. -llib -O3
	LD_LIBRARY_PATH=. ./main.o