Lesson 20: Modern C++ Smart Pointers: unique_ptr, shared_ptr & RAII

💎 Modern C++ (C++11/14/17/20) Smart Pointers

Raw pointers (new / delete) are prone to memory leaks and double-free bugs. Modern C++ solves memory safety using Smart Pointers declared in <memory>.

🛡️ Smart Pointer Types

🔒 std::unique_ptr<T>: Sole, exclusive ownership. Zero overhead. Automatically deletes resource when going out of scope. Cannot be copied, only moved via std::move().

👥 std::shared_ptr<T>: Shared ownership using reference counting. Resource is freed when the last shared_ptr owner is destroyed.

🔗 std::weak_ptr<T>: Non-owning observer reference to a shared_ptr to break circular dependency memory leaks.

💻 Code Example: std::makeunique & std::makeshared

⊞C++ Source Code (main.cpp)

#include <iostream>

#include <memory>

class Widget {

public:

Widget() { std::cout << "💎 Widget Allocated on Heap" << std::endl; }

~Widget() { std::cout << "🧹 Widget Automatically Destructed (Zero Memory Leaks)" << std::endl; }

void execute() { std::cout << "⚡ Widget executing task..." << std::endl; }

};

int main() {

// Modern C++ Memory Allocation (No explicit delete required!)

std::unique_ptr<Widget> w1 = std::make_unique<Widget>();

w1->execute();

// Transfer ownership using std::move

std::unique_ptr<Widget> w2 = std::move(w1);

if (!w1) std::cout << "w1 is now null after std::move ownership transfer." << std::endl;

return 0;

} // w2 goes out of scope here -> Widget destructor fires automatically!

⊞Windows 11 Pro Terminal Execution OutputWindows 11 Pro Verified

⊞Administrator: Windows 11 Pro Command Prompt (g++ GCC 13.2.0)

—□✕

Microsoft Windows [Version 10.0.22631.3007] (Windows 11 Pro x86_64)

C:\Users\Student\CPP_Project>#include <iostream>

C:\Users\Student\CPP_Project> g++ -o main.exe main.cpp C:\Users\Student\CPP_Project> main.exe Hello World from C++ on Windows 11 Pro! [Process exited with code 0 in 0.001 seconds]

> ⊞ Windows Tip: Modern C++ smart pointers make memory safety in Windows 11 enterprise C++ codebases automatic, clean, and bug-free!

💎 Modern C++ (C++11/14/17/20) Smart Pointers

🛡️ Smart Pointer Types

💻 Code Example: std::makeunique & std::makeshared

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