why does value allocated in stack didn't result in double free pointer?

Please tell me why didn’t result in double free pointer that the value is allocated in stack? Thanks.

#[test]
fn read_value_that_allocated_in_stack_is_no_problem() {
    let origin = Value(1);
    let copied = unsafe { std::ptr::read(&origin) };

    assert_eq!(copied, Value(1));
    assert_eq!(copied, origin);
}

/// test failed as expected: double free detected
#[test]
fn read_value_that_allocated_in_heap_will_result_in_double_free_problem() {
    let origin = Box::new(Value(1));
    let copied = unsafe { std::ptr::read(&origin) };

    assert_eq!(copied, Box::new(Value(1)));
    assert_eq!(copied, origin);
}


#[derive(Debug, PartialEq)]
struct Value<T>(T);

>Solution :

The unsafe method you are using just creates a bitwise copy of the referenced value. When you do this with a Box, it’s not okay but for something like your Value struct containing an integer, it is okay to make the copy as Drop of integers has no side effects while drop of Box accesses global allocator and changes the state.

If you do not understand any term I used for this explanation, try to search it or ask in the comments.