C Memory Management Explained

Manual Memory Management

Unlike Python or Java, C has no garbage collector. You allocate and free memory yourself, which gives control but demands discipline.

Stack vs Heap

	Stack	Heap
Speed	Fast	Slower
Size	Limited	Large
Lifetime	Auto (scope)	Manual (free)

The Four Allocation Functions

int *a = malloc(sizeof(int) * 10);   // uninitialised
int *b = calloc(10, sizeof(int));    // zero-initialised
b = realloc(b, sizeof(int) * 20);    // resize
free(a); free(b);                    // release

Avoiding Memory Leaks

• Every malloc needs a matching free.
• Set pointers to NULL after freeing.
• Use tools like Valgrind to detect leaks.

FAQs

What is a dangling pointer?

A pointer to memory that's already been freed. Using it is undefined behaviour. More in our C guides.

Double free?

Calling free twice on the same pointer crashes — set it to NULL after freeing.