C++ Mutex Lock

std::lock_guard vs std::scoped_lock §

• std::lock_guard has an API that is a little safer to use than std::scoped_lock. No compile error for the following example if using std::scoped_lock

## Incorrect usage
{
   std::scoped_lock lock;  // protect this block
}
 
## Correct usage
{
   std::scoped_lock lock{mut};  // protect this block
}

• General Advice

1. lock_guard if you need to lock exactly 1 mutex for an entire scope.
2. scoped_lock if you need to lock a number of mutexes that is not exactly 1.
3. unique_lock if you need to unlock within the scope of the block (which includes use with a condition_variable).