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What is the difference between the stack and the heap? What do new and delete do? What is a dangling pointer and how does it arise? What is the difference between malloc/free and new/delete? What is placement new? What causes a stack overflow? What is RAII and how does it relate to memory management? What is the difference between shallow copy and deep copy in memory terms? What is memory alignment and why does it matter? What is the difference between a memory leak and a resource leak?
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C++ › Memory Management

What is a memory leak?

Beginner

Answer

A memory leak occurs when heap memory is allocated but never freed, so it remains reserved for the program's lifetime, gradually exhausting available memory. Leaks happen when a delete is missed, a pointer is overwritten before freeing, or an exception skips the cleanup. RAII/smart pointers prevent most leaks.
int* p = new int(1);
p = new int(2);   // first allocation leaked
Real-world example A long-running server slowly consumes all memory because a handler forgets to free per-request buffers.

Common follow-ups: How do smart pointers prevent leaks? | What tools detect leaks?

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All 12 Memory Management questions