Smart Pointers

Question 1

Smart Pointers

What does RAII stand for?

Answer 1

Resource Acquisition is Initialization

Question 2

What are the other two Acronyms RAII can be referred to as?

Answer 2

• CADRe (CTORs Acquire DTORs Release)
• SBRM (Scope Based Resource Management)

Question 3

What happens when a class falls out of scope?

Answer 3

Its DTOR is called

Question 4

What would prevent a stack variable’s DTOR from being called?

Answer 4

An unchecked error (uncaught throw or segfault)

Question 5

What is the first concept behind RAII?

Answer 5

That resource acquisition should be done during intialization.

Question 6

What is the importance Acquiring during Initialization?

Answer 6

Moving past this point confirms that all data was initizialized correctly.

Question 7

What is the second concept behind RAII?

Answer 7

That resources must be released when data is deallocated. (delete pointers, close files, etc.)

Question 8

What are Smart Pointers?

Answer 8

Objects that act as pointers.

Question 9

What library contains smart pointers?

Answer 9

<memory>

Question 10

What are the benefits of using smart pointers?

Answer 10

• Allow for CTORS and DTORS
• They can be put on the stack and passed around more easily
• Methods for working with data

Question 11

What are the 3 types of Smart Pointers?

Answer 11

• Unique
• Shared
• Weak

Question 12

What is a Unique Pointer?

Answer 12

A smart pointer that exclusively owns one object. It handles allocation, and deallocation of the object.

Question 13

How do you syntactically declare a unique pointer?

Answer 13

unique_ptr<type> ptrName(new type);

Question 14

What must the objects held by unique pointers have?

Answer 14

A DTOR. The unique_ptr will try to call this when deallocation occurs.

Question 15

When must you have a virtual DTOR?

Answer 15

When you have a Data Structure containing smart pointers to an inheritable object. Ensures DTORs can be called polymorphically.

Question 16

How do you copy data from one unique pointer to another?

Answer 16

Using the move() CTOR

Question 17

What is a Shared Pointer?

Answer 17

A smart pointer that allows multiple shared pointers to lay claim to an object. The object will only deallocate when there are no remaining pointers.

Question 18

How do you syntactically declare a shared pointer?

Answer 18

shared_ptr<type> ptrName(new Type);

Question 19

What is the benefit of shared pointers?

Answer 19

Allows copies of the pointer to be passed around referring to the same object without reinitializing.

Question 20

What is a weak pointer?

Answer 20

A smart pointer that can look at a shared pointer’s object without claiming ownership; i.e. it cannot prevent the object falling out of scope, it can just look.

Question 21

What are the two main use cases for weak pointers?

Answer 21

• Looking into cached data
• Preventing Circular dependencies (Ex: doubly linked list, front pointer is shared, back pointer is weak)