Garbage Collection

How runtimes reclaim memory automatically — from reference counting to mark-sweep and generational GC

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steps

Act 1 of 8·Manual Memory

step 1

int* p = new int[1000];  // allocate
use(p);
delete[] p;             // you must free

Speednormal

In C and C++ you manage memory by hand: every new/malloc needs a matching delete/free. Get it wrong and you hit two classic bugs. Forget to free → a memory leak (the program slowly eats all RAM). Free too early or twice → a dangling pointer / use-after-free (corruption or crash). Garbage Collection automates this: the runtime decides when memory is safe to reclaim, so you never call free yourself.

GC strategies

Reference countingO(1), prompt, misses cycles

Mark & sweeptracing by reachability

Generationalyoung dies fast → cheap

Concurrentshrink pause time

Active Recall

Question 1 / 3

Why can reference counting alone never reclaim a reference cycle?

Under the Hood

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DNSresolving host

TCPconnecting

TLShandshake

HTTPrequesting

DSAverse

Garbage Collection

Garbage Collection