Definition of thread safety

1.1.1 Definition of thread safety

According to [JCP], a thread-safe class should meet the following three conditions:

When multiple threads are accessed at the same time, they exhibit the correct behavior.

Regardless of how the operating system dispatches these threads, no matter how the order of execution of those threads is interleaved (interleaving).

The caller code does not require additional synchronization or other coordinated actions.

According to this definition, most of the classes in the C + + standard library are not thread-safe, including std::string, std::vector, std::map, etc., because these classes usually need to be externally locked for multiple threads to access simultaneously.

Definition of thread safety