std::lock_guard vs std::scoped_lock: Choosing the Right Lock for the Task

With the introduction of C 17, the std::scoped_lock class emerged alongside the existing std::lock_guard, raising questions about their differences and when to use each.

While std::scoped_lock shares similarities with std::lock_guard, it offers some crucial distinctions.

When to Use std::lock_guard:

• Use std::lock_guard when locking a single mutex for the entire duration of a scope.
• Its concise syntax makes it less prone to accidental usage errors than std::scoped_lock.

• Example:

  {
    std::lock_guard lock(my_mutex);
    // Code protected by lock
  }

When to Use std::scoped_lock:

• Use std::scoped_lock when the need for mutual exclusion involves multiple mutexes (either a specific count or a variadic template parameter pack).

• Example:

  std::scoped_lock lock(mutex1, mutex2);
  // Code protected by lock

Additional Considerations:

• Safety: While both classes provide thread-safe locking, std::lock_guard's API is slightly safer for scenarios where locking only one mutex is required.
• Compatibility: std::lock_guard is fully compatible with older C versions and provides backward compatibility.
• Default Constructor: std::lock_guard does not support constructors taking zero arguments, while std::scoped_lock allows for an empty parameter pack.

Conclusion:

The choice between std::lock_guard and std::scoped_lock depends on the specific locking requirements of the code. By understanding their similarities and differences, developers can leverage the appropriate lock class to ensure safe and efficient multi-threading.