You can't both cast a double* to an int* and then dereference the int* , expecting to read an int-sized chunk of the double. It's called strict aliasing and the

You can't both cast a double* to an int* and then dereference the int* , expecting to read an int-sized chunk of the double. It's called strict aliasing and there are defined scenarios where it is allowed (one is that char* is an alias for all pointers).