单击多个 wxButton 时，Linux C++ wxWidgets 出现分段错误

Question

I'm having issues with my wxWidgets application when clicking a wxButton then clicking another wxButton. The first click will go fine, and the event is handled alright, but the second click, whether it be on the same button or a different button, causes a segfault. I'm using Code::Blocks as my IDE on Ubuntu Linux. Here's my code for reference:

main.cpp

/***************************************************************
 * Name:      assignment7Main.cpp
 * Purpose:   Code for Application Frame
 * Author:    Nico ()
 * Created:   2020-03-05
 * Copyright: Nico ()
 * License:
 **************************************************************/

#include "wx_pch.h"
#include "assignment7Main.h"
#include <wx/msgdlg.h>
#include "wx/file.h"
#include "wx/url.h"
#include <fstream>

//(*InternalHeaders(assignment7Frame)
#include <wx/intl.h>
#include <wx/string.h>
//*)

//helper functions
enum wxbuildinfoformat {
    short_f, long_f };

wxString wxbuildinfo(wxbuildinfoformat format)
{
    wxString wxbuild(wxVERSION_STRING);

    if (format == long_f )
    {
#if defined(__WXMSW__)
        wxbuild << _T("-Windows");
#elif defined(__UNIX__)
        wxbuild << _T("-Linux");
#endif

#if wxUSE_UNICODE
        wxbuild << _T("-Unicode build");
#else
        wxbuild << _T("-ANSI build");
#endif // wxUSE_UNICODE
    }

    return wxbuild;
}

//(*IdInit(assignment7Frame)
const long assignment7Frame::ID_BUTTON1 = wxNewId();
const long assignment7Frame::ID_TEXTCTRL1 = wxNewId();
const long assignment7Frame::ID_BUTTON3 = wxNewId();
const long assignment7Frame::ID_TEXTCTRL2 = wxNewId();
const long assignment7Frame::ID_BUTTON2 = wxNewId();
const long assignment7Frame::ID_LISTBOX1 = wxNewId();
const long assignment7Frame::ID_GAUGE1 = wxNewId();
const long assignment7Frame::ID_PANEL1 = wxNewId();
const long assignment7Frame::idMenuQuit = wxNewId();
const long assignment7Frame::idMenuAbout = wxNewId();
const long assignment7Frame::ID_STATUSBAR1 = wxNewId();
//*)

BEGIN_EVENT_TABLE(assignment7Frame,wxFrame)
    //(*EventTable(assignment7Frame)
    //*)
END_EVENT_TABLE()

assignment7Frame::assignment7Frame(wxWindow* parent,wxWindowID id)
{
    //(*Initialize(assignment7Frame)
    wxBoxSizer* BoxSizer1;
    wxBoxSizer* BoxSizer2;
    wxBoxSizer* BoxSizer3;
    wxBoxSizer* BoxSizer4;
    wxBoxSizer* BoxSizer5;
    wxBoxSizer* BoxSizer6;
    wxBoxSizer* BoxSizer7;
    wxFlexGridSizer* FlexGridSizer1;
    wxFlexGridSizer* FlexGridSizer2;
    wxMenu* Menu1;
    wxMenu* Menu2;
    wxMenuBar* MenuBar1;
    wxMenuItem* MenuItem1;
    wxMenuItem* MenuItem2;
    wxStaticBoxSizer* StaticBoxSizer2;

    Create(parent, wxID_ANY, wxEmptyString, wxDefaultPosition, wxDefaultSize, wxDEFAULT_FRAME_STYLE, _T("wxID_ANY"));
    BoxSizer1 = new wxBoxSizer(wxHORIZONTAL);
    MainPanel = new wxPanel(this, ID_PANEL1, wxDefaultPosition, wxDefaultSize, wxTAB_TRAVERSAL, _T("ID_PANEL1"));
    FlexGridSizer1 = new wxFlexGridSizer(4, 1, 0, 0);
    FlexGridSizer2 = new wxFlexGridSizer(2, 2, 0, 0);
    BoxSizer2 = new wxBoxSizer(wxHORIZONTAL);
    URLButton = new wxButton(MainPanel, ID_BUTTON1, _("Select URL File"), wxDefaultPosition, wxDefaultSize, 0, wxDefaultValidator, _T("ID_BUTTON1"));
    BoxSizer2->Add(URLButton, 1, wxALL|wxALIGN_CENTER_HORIZONTAL|wxALIGN_CENTER_VERTICAL, 5);
    FlexGridSizer2->Add(BoxSizer2, 1, wxALL|wxALIGN_CENTER_HORIZONTAL|wxALIGN_CENTER_VERTICAL, 5);
    BoxSizer3 = new wxBoxSizer(wxHORIZONTAL);
    URLText = new wxTextCtrl(MainPanel, ID_TEXTCTRL1, _("Text"), wxDefaultPosition, wxSize(400,25), 0, wxDefaultValidator, _T("ID_TEXTCTRL1"));
    BoxSizer3->Add(URLText, 1, wxALL|wxALIGN_CENTER_HORIZONTAL|wxALIGN_CENTER_VERTICAL, 5);
    FlexGridSizer2->Add(BoxSizer3, 1, wxALL|wxALIGN_CENTER_HORIZONTAL|wxALIGN_CENTER_VERTICAL, 5);
    BoxSizer4 = new wxBoxSizer(wxHORIZONTAL);
    WordButton = new wxButton(MainPanel, ID_BUTTON3, _("Select Word FIle"), wxDefaultPosition, wxDefaultSize, 0, wxDefaultValidator, _T("ID_BUTTON3"));
    BoxSizer4->Add(WordButton, 1, wxALL|wxALIGN_CENTER_HORIZONTAL|wxALIGN_CENTER_VERTICAL, 5);
    FlexGridSizer2->Add(BoxSizer4, 1, wxALL|wxALIGN_CENTER_HORIZONTAL|wxALIGN_CENTER_VERTICAL, 5);
    BoxSizer5 = new wxBoxSizer(wxHORIZONTAL);
    WordText = new wxTextCtrl(MainPanel, ID_TEXTCTRL2, _("Text"), wxDefaultPosition, wxSize(400,25), 0, wxDefaultValidator, _T("ID_TEXTCTRL2"));
    BoxSizer5->Add(WordText, 1, wxALL|wxALIGN_CENTER_HORIZONTAL|wxALIGN_CENTER_VERTICAL, 5);
    FlexGridSizer2->Add(BoxSizer5, 1, wxALL|wxALIGN_CENTER_HORIZONTAL|wxALIGN_CENTER_VERTICAL, 5);
    FlexGridSizer1->Add(FlexGridSizer2, 1, wxALL|wxALIGN_CENTER_HORIZONTAL|wxALIGN_CENTER_VERTICAL, 5);
    BoxSizer6 = new wxBoxSizer(wxHORIZONTAL);
    GoButton = new wxButton(MainPanel, ID_BUTTON2, _("Go"), wxDefaultPosition, wxSize(100,30), 0, wxDefaultValidator, _T("ID_BUTTON2"));
    BoxSizer6->Add(GoButton, 1, wxALL|wxALIGN_CENTER_HORIZONTAL|wxALIGN_CENTER_VERTICAL, 5);
    FlexGridSizer1->Add(BoxSizer6, 1, wxALL|wxALIGN_CENTER_HORIZONTAL|wxALIGN_CENTER_VERTICAL, 5);
    StaticBoxSizer2 = new wxStaticBoxSizer(wxHORIZONTAL, MainPanel, _("Top URLs"));
    URLList = new wxListBox(MainPanel, ID_LISTBOX1, wxDefaultPosition, wxSize(600,300), 0, 0, wxVSCROLL, wxDefaultValidator, _T("ID_LISTBOX1"));
    StaticBoxSizer2->Add(URLList, 1, wxALL|wxALIGN_CENTER_HORIZONTAL|wxALIGN_CENTER_VERTICAL, 5);
    FlexGridSizer1->Add(StaticBoxSizer2, 1, wxALL|wxALIGN_CENTER_HORIZONTAL|wxALIGN_CENTER_VERTICAL, 5);
    BoxSizer7 = new wxBoxSizer(wxHORIZONTAL);
    ProgressGauge = new wxGauge(MainPanel, ID_GAUGE1, 100, wxDefaultPosition, wxSize(600,25), 0, wxDefaultValidator, _T("ID_GAUGE1"));
    BoxSizer7->Add(ProgressGauge, 1, wxALL|wxALIGN_CENTER_HORIZONTAL|wxALIGN_CENTER_VERTICAL, 5);
    FlexGridSizer1->Add(BoxSizer7, 1, wxALL|wxALIGN_CENTER_HORIZONTAL|wxALIGN_CENTER_VERTICAL, 5);
    MainPanel->SetSizer(FlexGridSizer1);
    FlexGridSizer1->Fit(MainPanel);
    FlexGridSizer1->SetSizeHints(MainPanel);
    BoxSizer1->Add(MainPanel, 1, wxALL|wxALIGN_CENTER_HORIZONTAL|wxALIGN_CENTER_VERTICAL, 5);
    SetSizer(BoxSizer1);
    MenuBar1 = new wxMenuBar();
    Menu1 = new wxMenu();
    MenuItem1 = new wxMenuItem(Menu1, idMenuQuit, _("Quit\tAlt-F4"), _("Quit the application"), wxITEM_NORMAL);
    Menu1->Append(MenuItem1);
    MenuBar1->Append(Menu1, _("&File"));
    Menu2 = new wxMenu();
    MenuItem2 = new wxMenuItem(Menu2, idMenuAbout, _("About\tF1"), _("Show info about this application"), wxITEM_NORMAL);
    Menu2->Append(MenuItem2);
    MenuBar1->Append(Menu2, _("Help"));
    SetMenuBar(MenuBar1);
    StatusBar1 = new wxStatusBar(this, ID_STATUSBAR1, 0, _T("ID_STATUSBAR1"));
    int __wxStatusBarWidths_1[1] = { -1 };
    int __wxStatusBarStyles_1[1] = { wxSB_NORMAL };
    StatusBar1->SetFieldsCount(1,__wxStatusBarWidths_1);
    StatusBar1->SetStatusStyles(1,__wxStatusBarStyles_1);
    SetStatusBar(StatusBar1);
    BoxSizer1->Fit(this);
    BoxSizer1->SetSizeHints(this);

    Connect(ID_BUTTON1,wxEVT_COMMAND_BUTTON_CLICKED,(wxObjectEventFunction)&assignment7Frame::OnURLButtonClick);
    Connect(ID_BUTTON3,wxEVT_COMMAND_BUTTON_CLICKED,(wxObjectEventFunction)&assignment7Frame::OnWordButtonClick);
    Connect(ID_BUTTON2,wxEVT_COMMAND_BUTTON_CLICKED,(wxObjectEventFunction)&assignment7Frame::OnGoButtonClick);
    Connect(idMenuQuit,wxEVT_COMMAND_MENU_SELECTED,(wxObjectEventFunction)&assignment7Frame::OnQuit);
    Connect(idMenuAbout,wxEVT_COMMAND_MENU_SELECTED,(wxObjectEventFunction)&assignment7Frame::OnAbout);
    //*)

    URLText->ChangeValue("");
    WordText->ChangeValue("");

    URLChosen = 0;
    WordChosen = 0;
}

assignment7Frame::~assignment7Frame()
{
    //(*Destroy(assignment7Frame)
    //*)
}

void assignment7Frame::OnQuit(wxCommandEvent& event)
{
    Close();
}

void assignment7Frame::OnAbout(wxCommandEvent& event)
{
    wxString msg = wxbuildinfo(long_f);
    wxMessageBox(msg, _("Welcome to..."));
}

void assignment7Frame::OnURLButtonClick(wxCommandEvent& event)
{
    if (URLChosen) {
        for (int i = 0; i < urlsCnt; i++)
            delete[] urls[i];
    }

    wxFileDialog dlg(this, wxT("Open .txt file containing URLs"), "", "", "Data files (*.txt)|*.txt", wxFD_OPEN | wxFD_FILE_MUST_EXIST);

    if (dlg.ShowModal() == wxID_OK) {
        wxFile urlFile(dlg.GetPath(), wxFile::read);

        URLText->ChangeValue(dlg.GetPath());

        if (urlFile.IsOpened()) {
            //read file to filestring
            urlFile.ReadAll(urlFileStringPtr);
            urlFile.Close();
        }
    }
    else
        return;

    std::string s = urlFileString.ToStdString();
    urlsCnt = 0;

    char * temp = new char[s.size() + 1];
    std::copy(s.begin(), s.end(), temp);
    temp[s.size()] = '\0'; // don't forget the terminating 0

    for (int i = 0, j = 0; i < strlen(temp); i++) {
        if (s[i] == '\n') {
            urls[urlsCnt] = new char[i - j + 1];

            for (int x = 0; x < i - j; x++)
                urls[urlsCnt][x] = temp[j+x];

            urls[urlsCnt][i-j-1] = '\0';

            urlsCnt++;
            j = i;
        }
    }

    URLChosen = 1;
}

void assignment7Frame::OnWordButtonClick(wxCommandEvent& event)
{
    if (WordChosen) {
        for (int i = 0; i < wordsCnt; i++)
            delete[] words[i];
    }

    wxFileDialog dlg(this, wxT("Open .txt file containing target words"), "", "", "Data files (*.txt)|*.txt", wxFD_OPEN | wxFD_FILE_MUST_EXIST);

    if (dlg.ShowModal() == wxID_OK) {
        wxFile wordFile(dlg.GetPath(), wxFile::read);

        WordText->ChangeValue(dlg.GetPath());

        if (wordFile.IsOpened()) {
            wordFile.ReadAll(wordFileStringPtr);
            wordFile.Close();
        }
    }
    else
        return;

    std::string s = wordFileString.ToStdString();
    wordsCnt = 0;

    char * temp = new char[s.size() + 1];
    std::copy(s.begin(), s.end(), temp);
    temp[s.size()] = '\0'; // don't forget the terminating 0

    for (int i = 0, j = 0; i < strlen(temp); i++) {
        if (s[i] == '\n') {
            words[wordsCnt] = new char[i - j + 1];

            for (int x = 0; x < i - j; x++)
                words[wordsCnt][x] = temp[j+x];

            words[wordsCnt][i-j-1] = '\0';

            wordsCnt++;
            j = i;
        }
    }

    WordChosen = 1;
}

void assignment7Frame::OnGoButtonClick(wxCommandEvent& event)
{
    if (URLChosen && WordChosen) {
        ProgressGauge->SetValue(33);
        wxURL url(urls[0]);

        if (url.GetError() == wxURL_NOERR) {
            wxInputStream *in_stream;
            in_stream = url.GetInputStream();
        }
        else {
            wxString msg("not working");
            wxMessageBox(msg, _("PROCESSING ERROR"));
        }
    }
    else {
        wxString msg("Error, can't process without both URL file and word file chosen. Please choose file.");
        wxMessageBox(msg, _("PROCESSING ERROR"));
    }
}

main.h

/***************************************************************
 * Name:      assignment7Main.h
 * Purpose:   Defines Application Frame
 * Author:    Nico ()
 * Created:   2020-03-05
 * Copyright: Nico ()
 * License:
 **************************************************************/

#ifndef ASSIGNMENT7MAIN_H
#define ASSIGNMENT7MAIN_H

//(*Headers(assignment7Frame)
#include <wx/button.h>
#include <wx/frame.h>
#include <wx/gauge.h>
#include <wx/listbox.h>
#include <wx/menu.h>
#include <wx/panel.h>
#include <wx/sizer.h>
#include <wx/statusbr.h>
#include <wx/textctrl.h>
//*)

#include <string>

//using namespace std;

class assignment7Frame: public wxFrame
{
    public:

        assignment7Frame(wxWindow* parent,wxWindowID id = -1);
        virtual ~assignment7Frame();

    private:

        //(*Handlers(assignment7Frame)
        void OnQuit(wxCommandEvent& event);
        void OnAbout(wxCommandEvent& event);
        void OnURLButtonClick(wxCommandEvent& event);
        void OnWordButtonClick(wxCommandEvent& event);
        void OnGoButtonClick(wxCommandEvent& event);
        //*)

        //(*Identifiers(assignment7Frame)
        static const long ID_BUTTON1;
        static const long ID_TEXTCTRL1;
        static const long ID_BUTTON3;
        static const long ID_TEXTCTRL2;
        static const long ID_BUTTON2;
        static const long ID_LISTBOX1;
        static const long ID_GAUGE1;
        static const long ID_PANEL1;
        static const long idMenuQuit;
        static const long idMenuAbout;
        static const long ID_STATUSBAR1;
        //*)

        //(*Declarations(assignment7Frame)
        wxButton* GoButton;
        wxButton* URLButton;
        wxButton* WordButton;
        wxGauge* ProgressGauge;
        wxListBox* URLList;
        wxPanel* MainPanel;
        wxStatusBar* StatusBar1;
        wxTextCtrl* URLText;
        wxTextCtrl* WordText;
        //*)

        wxString urlFileString;
        wxString * urlFileStringPtr = &urlFileString;

        wxString wordFileString;
        wxString * wordFileStringPtr = &wordFileString;

        int URLChosen;
        int WordChosen;

        int urlsCnt;
        int wordsCnt;

        char * urls[];
        char * words[];

        DECLARE_EVENT_TABLE()
};

#endif // ASSIGNMENT7MAIN_H

debugger info

Active debugger config: GDB/CDB debugger:Default
Building to ensure sources are up-to-date
Selecting target: 
Debug
Adding source dir: /home/dawbuntu/GUI/assignment7/
Adding source dir: /home/dawbuntu/GUI/assignment7/
Adding file: /home/dawbuntu/GUI/assignment7/bin/Debug/assignment7
Changing directory to: /home/dawbuntu/GUI/assignment7/.
Set variable: LD_LIBRARY_PATH=.:/usr/lib/x86_64-linux-gnu:
Starting debugger: /usr/bin/gdb -nx -fullname -quiet  -args /home/dawbuntu/GUI/assignment7/bin/Debug/assignment7
done
Setting breakpoints
Debugger name and version: GNU gdb (Ubuntu 8.1-0ubuntu3) 8.1.0.20180409-git
Child process PID: 5677
In gtk_widget_style_get_valist () (/usr/lib/x86_64-linux-gnu/libgtk-x11-2.0.so.0)
#23 0x000055555556b0e1 in assignment7Frame::OnWordButtonClick (this=0x555555888dd0, event=...) at /home/dawbuntu/GUI/assignment7/assignment7Main.cpp:229
/home/dawbuntu/GUI/assignment7/assignment7Main.cpp:229:8826:beg:0x55555556b0e1
At /home/dawbuntu/GUI/assignment7/assignment7Main.cpp:229
Continuing...
Program terminated with signal SIGSEGV, Segmentation fault.
Debugger finished with status 0

picture of GUI GUI pic one GUI pic two

The program keeps crashing and segfaulting whenever the second event is triggered, wherever that is. I'm guessing it's wxSmith and Code::Block's automatic generation of code for the GUI, but I'm unsure since I'm fairly new to wxWidgets. Help much appreciated.

Answer 1

This is the problem:

char * urls[];
char * words[];

These are called "flexible array members" and they are not valid in C++ .

Try to use something like:

std::vector<std::string> urls;
std::vector<std::string> words;

instead. Obviously you would need to adjust the rest of the code to use the new datatypes for urls and words.