c++继承时分段错误

C++ - segmentation fault when inheritance

本文关键字：错误 分段 继承 c++      更新时间：2023-10-16

我得到了非常奇怪的行为与我的非常简单的例子，崩溃时，我使用继承(class NapanaApplication : public QGuiApplication)，但不崩溃和工作正常时，直接使用QGuiApplication。

代码如下所示，NapanaApplication不做任何事情，只是继承了QGuiApplication。

怎么了?

SOLVED:我找到了一个原因。这是因为QGuiApplication将argc作为引用，而NapanaApplication构造函数不这样做。它不会产生任何错误，但它会导致QGuiApplication使用一些临时的argc变量而不是main的变量进行操作。

main.cpp 

#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:当QString::fromLocal8Bit中调用strlen时它崩溃了。 char*指针上的strlen被调用有值0x21，我不明白为什么，它应该可能是argv的东西。

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

注意QGuiApplication的签名:

QGuiApplication(int & argc, char ** argv)

你的函数有int argc代替。当整数值被父类构造函数视为引用时，我认为您正在引起段错误。

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