Concurrency is becoming increasingly important in today's programming world, and C++20 brings a number of advances in concurrency that enable developers to write multithreaded applications more efficiently and safely. These advancements mainly include:
- Scoped Threads
- Stop Tokens
Scoped Threads
Traditional thread management often requires developers to manually ensure that threads are properly cleaned up and resources are released, which is an error-prone and cumbersome process. Scope threading solves this problem. When a scope ends, the threads associated with it are automatically cleaned up without the developer having to manually handle them, greatly reducing the risk of resource leakage.
The following are examples of usage:
{
std::jthread myThread([&] {
// Tasks performed by the thread
});
}
// myThread is automatically cleaned up and terminated when it leaves this scope
Stop Tokens
In practice, we often need to stop running threads dynamically, e.g. in response to a user's stop operation or in response to a system state change. Stop tokens provide an elegant and secure way to accomplish this.
For example, in a media player, when the user clicks the "Stop Play" button, a stop token can be set to notify the thread that is decoding and playing audio to stop working.
std::stop_source source;
std::stop_token token = source.get_token();
std::jthread decodingThread([token] {
while (!token.stop_requested()) {
// Code for audio decoding
}
});
// User clicks to stop playback
source.request_stop();
Note that here std::stop_source can generate multiple instances of std::stop_token.
These concurrency improvements in C++20 not only increase programming efficiency, but also enhance code reliability and maintainability. They enable developers to handle complex concurrency scenarios more safely and write more robust and high-performance applications.