Export function that returns array of doubles

Question

In Golang how to export the function that returns array of doubles. The way it was possible before seems to return "runtime error: cgo result has Go pointer" now:

//export Init
func Init(filename string) (C.int, unsafe.Pointer) {
    var doubles [10]float64
    doubles[3] = 1.5
    return 10, unsafe.Pointer(&doubles[0])
}

Answer 1

In order to safely store a pointer in C, the data it points to must be allocated in C.

//export Init
func Init(f string) (C.size_t, *C.double) {
    size := 10

    // allocate the *C.double array
    p := C.malloc(C.size_t(size) * C.size_t(unsafe.Sizeof(C.double(0))))

    // convert the pointer to a go slice so we can index it
    doubles := (*[1<<30 - 1]C.double)(p)[:size:size]
    doubles[3] = C.double(1.5)

    return C.size_t(size), (*C.double)(p)
}