Hello!
I have got a class SmsGui which contains 2 forms generated by qtdesigner: mainWindow and loginWindow. Firstly when program runs, mainWidnow is created and shown. When user presses Ok on mainWindow, loginWindow is created and shown. And here are 2 situations: in first situation I do:
Qt Code: 
  1. connect(loginWindow->cancelButton, SIGNAL(clicked()), loginWindow, SLOT(close()));
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And loginDialog closes normally. But in a secod situation I call loginDialog->close() manually.
Qt Code: 
  1. connect(loginWindow->cancelButton, SIGNAL(clicked()), this, SLOT(kill()));
  2.  
  3. void SmsGui::kill()
  4. {
  5. 	loginDialog->close();
  6. }
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And this gives me a segfault. Why? I just call the same function but in 2 different ways, so why it gives me a segfault?
Backtrace:
Qt Code: 
  1. Program received signal SIGSEGV, Segmentation fault.
  2. [Switching to Thread -1223948608 (LWP 25558)]
  3. 0x0804d9a4 in SmsGui::kill (this=0x8061670) at sms_gui.cpp:125
  4. 125             loginDialog->close();
  5. (gdb) backtrace
  6. #0  0x0804d9a4 in SmsGui::kill (this=0x8061670)
  7.     at sms_gui.cpp:125
  8.  
  9. #1  0x0804d995 in SmsGui::clickedLoginOk (this=0x8061670)
  10.     at sms_gui.cpp:120
  11. #2  0x08050d14 in SmsGui::qt_metacall (this=0x8061670, 
  12.     _c=QMetaObject::InvokeMetaMethod, _id=5, _a=0xbfa59790)
  13.     at moc_sms_gui.cpp:83
  14. #3  0xb746132c in QMetaObject::activate ()
  15.    from /usr/lib/qt4/libQtCore_debug.so.4
  16. #4  0xb746157e in QMetaObject::activate ()
  17.    from /usr/lib/qt4/libQtCore_debug.so.4
  18. #5  0xb7e011f6 in QAbstractButton::clicked ()
  19.    from /usr/lib/qt4/libQtGui_debug.so.4
  20. #6  0xb7c66455 in QAbstractButtonPrivate::click ()
  21.    from /usr/lib/qt4/libQtGui_debug.so.4
  22. #7  0xb7c67779 in QAbstractButton::mouseReleaseEvent ()
  23.    from /usr/lib/qt4/libQtGui_debug.so.4
  24. #8  0xb7a3879d in QWidget::event ()
  25.    from /usr/lib/qt4/libQtGui_debug.so.4
  26. #9  0xb7c6761b in QAbstractButton::event ()
  27.    from /usr/lib/qt4/libQtGui_debug.so.4
  28. #10 0xb7ce0d52 in QPushButton::event ()
  29.    from /usr/lib/qt4/libQtGui_debug.so.4
  30. #11 0xb79ecea7 in QApplicationPrivate::notify_helper ()
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Header file:
Qt Code: 
  1. #ifndef SMS_GUI_H
  2. #define SMS_GUI_H
  3.  
  4. #include <QDialog>
  5. #include "ui_main_window.h"
  6. #include "ui_login_dialog.h"
  7. #include "types.h"
  8.  
  9. class SmsGui : public QObject
  10.  
  11. {
  12.  
  13. 	Q_OBJECT
  14.  
  15. 	public:
  16. 		QString username, password, number, message;
  17. 		bool limitCheck;
  18. 		unsigned short int port;
  19. 		void destroy();
  20. 		void showMainWindow();
  21.  
  22. 		void connectSlots();
  23. 		void disconnectSlots();
  24. 		void setMiastoPlusaParameters();
  25. 		void showLoginDialog();
  26. 		Ui_mainWindow *mainWindow;
  27. 		QDialog *mainDialog;
  28.  
  29. 		Ui_loginDialog *loginWindow;
  30. 		QDialog *loginDialog;
  31.  
  32.  
  33.  
  34. 	public slots:
  35. 		void enableSendButtonText();
  36. 		void enableSendButtonLine(const QString &newText);
  37. 		void resetAll();
  38. 		void currentIndexChanged(int index);
  39. 		void clickedLoginOk();
  40. 		void clickedSend();
  41. 		void clickedLoginCancel();
  42.  
  43. 		void closeMainWindow();
  44. 		void kill();
  45. 	public:
  46. 		SmsGui();
  47. 		~SmsGui();
  48.  
  49. 	signals:
  50. 		void readyToSend(network);
  51.  
  52.  
  53. };
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source:
Qt Code: 
  1. #include "sms_gui.h"
  2.  
  3. SmsGui::SmsGui()
  4. {
  5. 	showMainWindow();
  6. 	connectSlots();
  7. }
  8.  
  9. SmsGui::~SmsGui()
  10. {
  11. 	closeMainWindow();
  12. }
  13.  
  14. void SmsGui::showMainWindow()
  15. {
  16. 	mainDialog = new QDialog;
  17. 	mainWindow = new Ui_mainWindow;
  18. 	mainWindow->setupUi(mainDialog);
  19. 	mainDialog->show();
  20. }
  21.  
  22. void SmsGui::closeMainWindow()
  23. {
  24. 	mainDialog->reject();
  25. 	delete mainDialog;
  26. 	mainDialog = NULL;
  27. 	delete mainWindow;
  28. 	mainWindow = NULL;
  29. }
  30.  
  31. void SmsGui::connectSlots()
  32. {
  33. 	connect(mainWindow->okButton, SIGNAL(clicked()), this, SLOT(clickedSend()));
  34. }
  35.  
  36.  
  37. void SmsGui::clickedSend()
  38. {
  39. 	//mainDialog->close();
  40. 	switch(mainWindow->comboBox->currentIndex())
  41. 	{
  42. 		case 0: setMiastoPlusaParameters(); return;
  43. 		case 1: /*setPlusWWWParameters();*/ return;
  44. 		default: return;	
  45. 	}
  46. }
  47.  
  48. void SmsGui::showLoginDialog()
  49. {
  50. 	QDialog *loginDialog = new QDialog;
  51. 	loginWindow = new Ui_loginDialog;
  52. 	loginWindow->setupUi(loginDialog);
  53. 	connect(loginWindow->okButton, SIGNAL(clicked()), this, SLOT(clickedLoginOk()));
  54. 	connect(loginWindow->cancelButton, SIGNAL(clicked()), this, SLOT(clickedLoginCancel()));
  55. 	loginDialog->show();
  56. }
  57.  
  58. void SmsGui::clickedLoginOk()
  59. {
  60.  
  61. 	kill();
  62. }
  63.  
  64. void SmsGui::kill()
  65. {
  66. 	loginDialog->close();
  67. }
  68.  
  69.  
  70. void SmsGui::clickedLoginCancel()
  71. {
  72. 	loginDialog->close();
  73. }
  74.  
  75. void SmsGui::setMiastoPlusaParameters()
  76. {
  77. 	showLoginDialog();
  78. }
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