Cannot debug console app with gdb

I created a new Qt console app using Creator's wizard. I set it to run in terminal and replaced main.cpp with the following:

#include <iostream>

int main(int argc, char *argv[])
{
    int i = 0;
    while(1)
        std::cout << "test " << ++i << std::endl;
}

I built this with MinGW. Running is fine but when I try to debug the terminal window opens without any visible output and that's it. Closing the terminal shows the attached popup.