app1:

#include <iostream>

int main(int, char *[])
{
    std::string s;
    while (1)
    {
        std::cin >> s;
        std::cout << s;
    }

    return 0;
}

app2 (Qt):

#include <QProcess>

int main(int, char *[])
{
    QProcess p;
    p.start("/home/my/dev/build-app2-Desktop_Qt_5_5_1_GCC_64bit-Debug/app2");
    for (quint64 i = 0; i < 100000; i++)
        p.write("0000000000000000000000000000000000000000000000000000000\n");


    QString s = p.readAllStandardOutput(); //crash after this called


    return 0;
}