How to keep threads untangled when changing vector? c-CodePudding

This program will crash cause the threads are tangled... One could be pushing while the other is trying to erase.

How can I make this work?

#include <thread>
#include <vector>

using namespace std;

vector<int> v_test;

void push()
{
    v_test.push_back(0);
}

void erase()
{
    if (v_test.size() > 0)
    {
        v_test.erase(v_test.begin());
    }
}

int main()
{
    thread w0(push);
    thread w1(erase);

    while (true) { Sleep(1000); }
    return 0;
}

CodePudding user response：

You need to synchronize the threads so they coordinate their access to the vector. For example, by using a std::mutex, eg:

#include <thread>
#include <mutex>
#include <vector>
using namespace std;

vector<int> v_test;
mutex m_sync;

void push()
{
    lock_guard<mutex> lock(m_sync);
    v_test.push_back(0);
}

void erase()
{
    lock_guard<mutex> lock(m_sync);
    if (v_test.size() > 0)
    {
        v_test.erase(v_test.begin());
    }
}

int main()
{
    thread w0(push);
    thread w1(erase);

    while(true) {Sleep(1000);}
    return 0;
}