C++ - 继承时的分段错误

Question

我的非常简单的例子在我使用inheritance(class NapanaApplication : public QGuiApplication)时崩溃了,但是在直接使用时没有崩溃并正常工作QGuiApplication.

代码完全如下所示,NapanaApplication没有做任何事情,只是继承自QGuiApplication.

怎么了？

解决:我找到了一个理由.这是因为QGuiApplication取argc作为参考,但NapanaApplication构造却没有.它不会产生任何错误,但它会导致QGuiApplication操作一些临时argc变量而不是一个临时变量main.

main.cpp中

#include "napanaapplication.h"
#include "napanawindow.h"

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

    /*NapanaApplication app(argc, argv);*/ // segmentation fault

    QGuiApplication app(argc, argv); // no error        

    NapanaWindow win;

    win.resize(800, 600);
    win.show();

    return app.exec();
}

napanaapplication.h

#ifndef NAPANAAPPLICATION_H
#define NAPANAAPPLICATION_H

#include <QGuiApplication>

class NapanaApplication : public QGuiApplication
{

    Q_OBJECT

public:
    explicit NapanaApplication(int argc, char* argv[]);
signals:

public slots:
};

#endif // NAPANAAPPLICATION_H

napanapplication.c

#include "napanaapplication.h"

NapanaApplication::NapanaApplication(int argc, char* argv[]) : QGuiApplication(argc, argv) {}

调试器输出:strlen调用时崩溃QString::fromLocal8Bit.被调用的char*指针strlen有值0x21,我不明白为什么,它应该是来自的东西argv.

0   strlen  /usr/lib/debug/lib/x86_64-linux-gnu/libc-2.19.so    106 0x7ffff65c0aea  
1   QString::fromLocal8Bit  qstring.h   534 0x7ffff7142c11  
2   QCoreApplication::arguments qcoreapplication.cpp    2254    0x7ffff738503d  
3   sm_performSaveYourself  qxcbsessionmanager.cpp  188 0x7ffff05f5e3a  
4   sm_saveYourselfCallback qxcbsessionmanager.cpp  171 0x7ffff05f5cc9  
5   _SmcProcessMessage          0x7ffff014ad37  
6   IceProcessMessages          0x7fffeff3b8c7  
7   QSmSocketReceiver::socketActivated  qxcbsessionmanager.cpp  322 0x7ffff05f67e0  
8   QSmSocketReceiver::qt_static_metacall   qxcbsessionmanager.moc  68  0x7ffff05f6f88  
9   QMetaObject::activate   qobject.cpp 3718    0x7ffff73c097e  
10  QMetaObject::activate   qobject.cpp 3583    0x7ffff73c016c  
11  QSocketNotifier::activated  moc_qsocketnotifier.cpp 134 0x7ffff7458376  
12  QSocketNotifier::event  qsocketnotifier.cpp 296 0x7ffff73cb4db  
13  QCoreApplicationPrivate::notify_helper  qcoreapplication.cpp    1093    0x7ffff7382872  
14  QCoreApplication::notify    qcoreapplication.cpp    1038    0x7ffff7382554  
15  QGuiApplication::notify qguiapplication.cpp 1537    0x7ffff77f3076  
16  QCoreApplication::notifyInternal    qcoreapplication.cpp    965 0x7ffff738245e  
17  QCoreApplication::sendEvent qcoreapplication.h  224 0x7ffff7386087  
18  socketNotifierSourceDispatch    qeventdispatcher_glib.cpp   101 0x7ffff73f6afe  
19  g_main_context_dispatch         0x7ffff4f8dbd4  
20  ??          0x7ffff4f8de18  
21  g_main_context_iteration            0x7ffff4f8debc  
22  QEventDispatcherGlib::processEvents qeventdispatcher_glib.cpp   418 0x7ffff73f7799  
23  QPAEventDispatcherGlib::processEvents   qeventdispatcher_glib.cpp   115 0x7ffff0648906  
24  QEventLoop::processEvents   qeventloop.cpp  128 0x7ffff737f0b2  
25  QEventLoop::exec    qeventloop.cpp  204 0x7ffff737f373  
26  QCoreApplication::exec  qcoreapplication.cpp    1229    0x7ffff7382b36  
27  QGuiApplication::exec   qguiapplication.cpp 1528    0x7ffff77f3026  
28  main    main.cpp    13  0x40275a    

Answer 1

注意QGuiApplication的签名:

QGuiApplication(int & argc, char ** argv)

int argc相反,你的功能.我认为当整数值被父类构造函数视为引用时,您将导致段错误.