Thread-Safe Initialization

If the variable is never modified there is no need for synchronization by using an expensive lock or an atomic. You only have to ensure that it is initialized in a thread-safe way.

There are three ways in C++ to initialize variables in a thread-safe way.

1. Constant expressions.
2. The function std::call_once in combination with the flag std::once_flag.
3. A static variable with block scope.

Thread-safe initialisation in the main-thread

The easiest and fourth way to initialise a variable in a thread-safe way: initialise the variable in the main-thread before you create any child threads.

We will explain each thread-safe initialization method in the next 3 lessons.