Qt QProcess抱怨QThread ::開始，線程創建錯誤

Question

我有一個非常簡單的應用程序，應該使用QProcess做一些systemd控制。然後整個程序在下面。我每次運行應用程序，它具有以下抱怨：

QThread::start: Thread creation error: Resource temporarily unavailable 

我打印出線程的最大數量與_POSIX_THREAD_THREADS_MAX一個過程，它打印64.我也可以在命令行中運行使用QProcess命令只是罰款沒有問題。是什麼賦予了？

代碼：

int main(int argc, char *argv[]) 
{ 
    QCoreApplication a(argc, argv); 

    // Get the command line parameter to turn wifi on or off 
    QString wifiSwitch = argv[1]; 

    // Print the number of threads available 
    qDebug() << "Single Process can spawn this many threads:" << _POSIX_THREAD_THREADS_MAX; 

    // Switch based on the input and control wifi with systemctl 
    if (wifiSwitch == "on") { 

     // Subprocess systemd 
     QProcess controlWifi; 
     controlWifi.start("systemctl start wiap.service"); 
     controlWifi.waitForFinished(); 

     // Grab the output and use it to determine whether we successfully turned on the wifi 
     QString didTurnOnWifi = QString(controlWifi.readAll()).trimmed(); 
     controlWifi.close(); 

     // So if there is no error messages from the subprocess we were successful 
     if (didTurnOnWifi.length() == 0) { 
      qDebug() << "SUCCESS"; 
      exit(0); 
     } 
     else { 
      qDebug() << "FAILURE"; 
      exit(-1); 
     } 

    } 
    else if (wifiSwitch == "off") { 

     // Subprocess systemd 
     QProcess controlWifi; 
     controlWifi.start("systemctl stop wiap.service"); 
     controlWifi.waitForFinished(); 

     // Grab the output and use it to determine whether we successfully turned on the wifi 
     QString didTurnOnWifi = QString(controlWifi.readAll()).trimmed(); 
     controlWifi.close(); 

     // So if there is no error messages from the subprocess we were successful 
     if (didTurnOnWifi.length() == 0) { 
      qDebug() << "SUCCESS"; 
     } 
     else { 
      qDebug() << "FAILURE"; 
     } 

    } 
    else { 

     // No arguments 
     qDebug() << "FAILURE: You didn't specify any command line arguments, call this program like './fluke-control-wifi on|of'"; 
     exit(-1); 

    } 

    return a.exec(); 
} 

注：筆者近日從Qt的4.8.3升級到4.8.4的Qt但真的不應該打破QProcess中..我也無法找到一個bug報告。

Answer 1

嘗試增加

if(!controlWifi.waitForStarted()) 
{ 
    qDebug("Error starting process\n"); 
    return; 
} 

只是通話開始後。