Brownian Bridge™

1. A `Matrix` class owns a heap-allocated buffer via `double* _data`. You define a destructor that calls `delete[] _data`. You do **not** define a copy constructor. What happens when you write `Matrix b = a;`?

A deep copy is made: `b._data` points to a new heap buffer with the same valuesA shallow copy is made: `b._data` and `a._data` point to the same heap buffer; when either destructor fires, the other holds a dangling pointerThe compiler refuses to compile the statement because `Matrix` defines a destructorThe statement is equivalent to `Matrix b; b = a;` and calls copy assignment instead

2. What does the following copy assignment operator do incorrectly? ```cpp Matrix& Matrix::operator=(const Matrix& other) { delete[] _data; _n = other._n; _data = new double[_n]; std::copy(other._data, other._data + _n, _data); return *this; } ```

It fails to return `*this`It does not handle self-assignment: `a = a` deletes `_data` and then reads from the freed memory when copying from `other`It should use `malloc` instead of `new[]`It leaks memory because `delete[]` is not matched with a `new[]`

3. After a move operation, the moved-from object is in a **destroyed** state and can no longer be used in any way.

truefalse

4. Which function signature correctly declares a **move constructor** for `class Matrix`?

`Matrix(const Matrix& other)``Matrix(Matrix other)``Matrix(Matrix&& other) noexcept``Matrix&& Matrix(Matrix& other)`

5. In the copy-and-swap idiom for copy assignment: ```cpp Matrix& operator=(Matrix other) { swap(*this, other); return *this; } ``` When is the destructor called on the old resource?

Immediately when `swap` is calledWhen the function returns and `other` (which now holds the old resource) goes out of scopeWhen `*this` is subsequently destroyedIt is never called — the old resource is leaked

6. If you declare `Matrix(const Matrix&) = delete;`, then writing `Matrix b = a;` is a compile error, but `Matrix b(std::move(a));` is still valid (assuming a move constructor exists).

truefalse

Quiz: C++ Classes and Special Member Functions

Quick Quiz