结论:非线程安全
现象:程序会挂掉
#include <mutex>
#include <iostream>
#include <unordered_map>
using namespace std;
std::unordered_map<int, int> m;
void f()
{
while(1)
std::cout << m[-1];
}
int main()
{
m[-1] = -1;
std::thread t = std::thread(f);
for (int i = 0; i < 1000000; ++i)
{
m[i] = i;
}
t.join();
return 0;
}