[Bug libstdc++/89740] reading from cin & writing to cout sync_with_stdio(false) has race conditions

[ahu at ds9a dot nl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89740

--- Comment #1 from bert hubert <ahu at ds9a dot nl> ---
Comment on attachment 45981
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=45981
a small reproduction for this bug.

>#include <iostream>
>#include <thread>
>#include <string>
>#include <unistd.h>
>
>using namespace std;
>
>void theThread()
>{
>  for(int counter = 0 ;; ++counter) {
>    usleep(250000);
>    cout << "Hi "<< counter << endl;
>  }
>}
>
>int main()
>{
>  std::ios_base::sync_with_stdio(false);
>  // cin.tie(nullptr);
>  
>  string line;
>  thread t(theThread);
>  while(getline(cin, line))
>    ;
>}