RAII

Resource Acquisition Is Initialisation: tie every resource to an object's lifetime.

Intermediate

RAII means a resource (memory, file, mutex lock, interrupt disable) is acquired in a constructor and released in the destructor. Because destructors run automatically when objects leave scope — even during exceptions — leaks become almost impossible.

{
    std::lock_guard<std::mutex> lock(m);   // locks
    shared_counter++;
}                                          // unlocks automatically

Embedded example: a CriticalSection object that disables interrupts in its constructor and re-enables them in its destructor.

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