CS136 FINAL

Question 1

What are the advantages of HEAP

Answer 1

Dynamic - size of memory determined at runtime

Resizable - allocated memory can be “resized”

Scope - allocated memory “persists” until you free it; memory is valid even with function returns

Safety - if memory runs out, it can be detected and handled properly.

Question 2

Which library is malloc declared in?
What is the run time of Malloc

Answer 2

<stdlib.h>
runtime: O(1)
</stdlib.h>

Question 3

What does <stdlib.h> provide in general</stdlib.h>

Answer 3

anything memory allocation related.
EX: malloc, realloc, calloc, free, bsearch, qsort

Question 4

What does free do?
What is the runtime of free?
What happens when u print ptr again?

Answer 4

deallocates space that has been allocated. does nothing if ptr is NULL
invalidates pointer

runtime: O(1)

throws an error: heap-use-after-free

Question 5

What is a dangling pointer? What should we do to prevent this and why should we do it?

Answer 5

A pointer to a freed allocation.

Should assign NULL to a dangling pointer, this way there is no error when you free that pointer again.

Question 6

How does a memory leak occur with heap memory?

Answer 6

When allocated heap memory is not freed before program termination.

Question 7

what are the side effects of heap ?

Answer 7

it modifies the state of heap,

if memory is not freed within the func that allocates it then we need to document that
“caller must free”

if it is freeing memory that it didnt allocate
“data becomes invalid”

Question 8

Describe merge_sort

Answer 8

see answers on phone