Memory leak concepts - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a memory leak in C programming?

A memory leak happens when a program allocates memory but never frees it, causing the memory to stay used and unavailable for other parts of the program or system.

beginner

Why are memory leaks a problem in programs?

Memory leaks reduce the available memory over time, which can slow down or crash programs because they run out of memory to use.

beginner

Which C functions are commonly used to allocate and free memory?

malloc() is used to allocate memory, and free() is used to release that memory back to the system.

intermediate

What happens if you call free() on a pointer twice?

Calling free() twice on the same pointer can cause undefined behavior, which may crash the program or corrupt memory.

intermediate

How can you detect memory leaks in C programs?

You can use tools like Valgrind or AddressSanitizer to find memory leaks by tracking allocated memory that was never freed.

What does a memory leak cause in a program?

A Program runs faster

B Memory stays allocated and is never freed

C Memory is freed too early

D Memory is shared between programs

A memory leak means memory is allocated but not freed, causing it to stay used.

Which function is used to free allocated memory in C?

A free()

B delete()

C alloc()

D malloc()

free() releases memory that was allocated with malloc() or similar functions.

What is a common cause of memory leaks?

A Calling free() too many times

B Using global variables

C Forgetting to call free() after malloc()

D Writing to a file

Not freeing allocated memory causes memory leaks.

Which tool can help detect memory leaks in C programs?

A Valgrind

B GCC

C Make

D Git

Valgrind tracks memory usage and can find leaks.

What happens if you free memory twice?

A Memory is automatically reallocated

B Program runs normally

C Memory is doubled

D Undefined behavior, possible crash

Freeing memory twice can cause crashes or corrupt memory.

Explain what a memory leak is and why it is harmful in C programs.

Think about what happens when memory is allocated but never given back.

Describe how you can prevent memory leaks when using malloc() in C.

Consider the steps after allocating memory.