`std::thread::detach()` vs. `join()`: When Should I Use Each?

std::thread::detach() vs Join: When to Use Which

When utilizing std::thread for performance optimization, it's crucial to understand the difference between detaching a thread and not doing so. Join() halts the current thread until the target thread completes, but what happens when detach() is called or left out?

Not Detaching:

In the absence of detach(), the thread runs independently until the destructor of std::thread is invoked. If the thread has not been joined by then, std::terminate is called, leading to program termination.

Detaching:

Calling detach() explicitly terminates the thread's execution when its method finishes. This releases the thread from the control of the main program, leaving it to complete its tasks in the background. However, it is important to note that the thread's stack is not unwound when it terminates.

When to Use Join or Detach:

• Use Join:

  • When you need to ensure that all tasks in a thread are completed before continuing.

• Use Detach:

  • When you want to offload tasks to background threads and handle thread completion later or don't need to wait for specific completion times. In this case, you will need to implement your own synchronization mechanism to wait for the thread completion.

Important Considerations:

• Detached threads may leave unclosed resources, such as open files or locks.
• Unwound threads may corrupt shared memory or produce inconsistent data.
• It's generally recommended to use join() unless you have a compelling reason to detach a thread and are prepared to handle the potential consequences.

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