Allocating C memory when invoking C code via CGO

cgo_memory_alloc.go

// allocate 81 char string in C memory
parsed := C.CString(strings.Repeat("0", 81))
defer C.free(unsafe.Pointer(parsed)) // free it when we're done here

// allocate byte array for our image data in C memory
p := C.CBytes(data)
defer C.free(unsafe.Pointer(p)) // free it when we're done

// float32 is standardized type compatible with C
gridCoords := []float32{-1, -1, -1, -1, -1, -1, -1, -1}

// C.ParseSudoku will write to the allocated memory
C.ParseSudoku((*C.char)(p), C.int(len(data)), (*C.float)(unsafe.Pointer(&gridCoords[0])), true, parsed)