C++: What is the difference between stack and heap allocation?

Stack allocation:

• Automatic lifetime (scope-based)
• Very fast (pointer bump)
• Limited size (typically 1-8 MB)
• No deallocation needed

1void function() {
2    int x = 10;           // stack
3    int arr[100];         // stack
4} // automatically freed

Heap allocation:

• Manual or smart pointer management
• Slower (system calls)
• Large size available
• Must be freed (or use smart pointers)

1void function() {
2    int* p = new int(10);            // heap
3    auto v = std::make_unique<int[]>(1000); // heap
4} // p leaked, v auto-freed

Best practices:

• Prefer stack allocation
• Use smart pointers for heap
• Avoid large stack objects