Scoped Locking¶

Explicit Unlocking Considered Dangerous ¶

What if a critical section throws?

lock.lock();
do_something_errorprone(); // possibly throws
do_more_of_it(); // possibly throws
lock.unlock();

Lock remains locked
⟶ Deadlock

RAII - Resource Acquisition Is Initialization ¶

Deterministic destructors

Objects are destroyed at end of block
Unlike Java, Python, … (garbage collection)
⟶ Exception safety!

Simplest: `std::lock_guard`¶

Obtains (single) lock in constructor
Releases lock in destructor
⟶ good for single lock

std::lock_guard¶

...
// critical section
{
  std::lock_guard<std::mutex> g(lock); // lock.lock()
  do_something_errorprone();
  do_more_of_it();
  // ~guard does lock.unlock();
}
...