What are some examples of thread-local storage in C++?

What are some examples of thread-local storage in C++?

Thread-local storage (TLS) allows you to create variables that are unique to each thread. For example, you can use the thread_local keyword in C++11 to declare a variable that is local to each thread.

Can you show me a code example?

Sure! Here's a simple example:

#include <iostream>
#include <thread>

thread_local int threadVar = 0;

void incrementVar() {
    threadVar++;
    std::cout << "Thread ID: " << std::this_thread::get_id() << " - Value: " << threadVar << std::endl;
}

int main() {
    std::thread t1(incrementVar);
    std::thread t2(incrementVar);
    t1.join();
    t2.join();
    return 0;
}

What happens if multiple threads access the same thread-local variable?

Each thread has its own instance of the thread-local variable, so they won't interfere with each other. Changes made by one thread won't affect the value seen by another thread.

Are there any performance considerations with using thread-local storage?

Yes, while thread-local storage can improve performance by avoiding locks, it can also lead to increased memory usage since each thread has its own copy of the variable. It's important to balance these factors based on your application's needs.