lst-0038-book.cpp
// https://godbolt.org/z/1j8W7GjTf
#include <iostream>
#include <string>
#include <thread>
#include <mutex>
thread_local unsigned int usage = 0;
static std::mutex cout_mutex;
void use(const std::string thread_name) {
++usage;
std::lock_guard lock(cout_mutex); // Protect output
std::cout << thread_name << ": " << usage << '\n';
}
int main() {
std::jthread a{use, "a"}, b{use, "b"};
use("main");
}