2. C++ Memory Model

Question 1

Every variable in C++ has these four things

Answer 1

• name
• type
• value
• memory location

Question 2

Which is larger, a memory location in the stack or the heap?

Answer 2

The stack.

Memory on the stack starts at the top and goes down, while memory on the heap starts at the bottom and goes up.

Question 3

How do you create a new variable on heap memory?

Answer 3

Use the “new” keyword. e.g., int *i = new int;

Question 4

What happens if a function returns a pointer to a local variable and then we try to assign something to the memory location the pointer is pointing to?

Answer 4

Unknown. Depending on the compiler settings, the compiler may report that the local variable address is being returned, which could be treated as a warning or as a compilation error; Or, if the program is allowed to compile then at runtime the program may terminate due to a memory fault.

Question 5

Suppose we declare a variable as “int i;” How would you get the address of the memory location containing the contents of variable i?

Answer 5

&i

Question 6

How many memory allocations are made on the stack and on the heap for the following code?

int i = 0;
int *j = &i;

Answer 6

Two allocations on the stack and zero allocations on the heap.

Question 7

How many memory allocations are made on the stack and on the heap for the following code?

int *i = new int;

Answer 7

One allocation on the stack and one allocation on the heap.

Question 8

Let’s say p is a pointer to a class with a variable a.

What is expression p->a is equivalent to?

Answer 8

(*p).a