TLS（Thread Local Storage）

这个技术主要解决多线程时，每个线程拥有自己独立的变量。

例如正常情况下，多线程共享变量

#include <iostream>
#include <thread>

static int counter = 0;  // Shared across all threads

void increment_counter() {
    counter++;
    std::cout << "Thread ID: " << std::this_thread::get_id()
              << ", Counter: " << counter << std::endl;
}

int main() {
    std::thread t1(increment_counter);
    std::thread t2(increment_counter);

    t1.join();
    t2.join();

    return 0;
}

结果
Thread ID: 140735680792320, Counter: 1
Thread ID: 140735672399616, Counter: 2

如果采用TLS技术，那么再count的最前面添加thread_local（ c++11）或 __thread (GCC/Clang)

#include <iostream>
#include <thread>

thread_local static int counter = 0;  // Each thread has its own copy

void increment_counter() {
    counter++;
    std::cout << "Thread ID: " << std::this_thread::get_id()
              << ", Counter: " << counter << std::endl;
}

int main() {
    std::thread t1(increment_counter);
    std::thread t2(increment_counter);

    t1.join();
    t2.join();

    return 0;
}

结果：
Thread ID: 140735680792320, Counter: 1
Thread ID: 140735672399616, Counter: 1