Синхронизация потоков через scoped_lock

// Example program
#include <iostream>
#include <string>
#include <thread>
#include <vector>
#include <iostream>
#include <stdarg.h>
#include <mutex>
 
using namespace std;
 
std::string format(const char *fmt, ...);
void start(const int f, const int t, vector<int>* vec);
 
std::mutex vecmgr;
 
int main()
{
    vector<int> vec;
    start(20, 40, &vec);
    start(100, 120, &vec);
    start(200, 240, &vec);
 
    string name;
    cout << "What is your name? ";
    getline(cin, name);
    cout << "Hello, " << name << "!\n";
 
    for (auto s: vec) {
        cout << s << ", ";
    }
    cout << endl;
 
}
 
void start(int f, int t, vector<int>* vec) {
    auto thfunc = [&f, &t, vec] () {
//        scoped_lock lock{vecmgr};
        if (f > t) return;
        for (int i=f; i<=t; i++) {
            vec->push_back( i );
        }
    };
    thread th(thfunc);
    th.join();
    // th.detach();
}