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GTK+ C++ compiler and signal handlers

This is a discussion on GTK+ C++ compiler and signal handlers within the C++ Programming forums, part of the General Programming Boards category; So, I'm using GTK+ library and GLADE gui constructor, but I'm getting an error when i compile the code in ...

  1. #1
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    GTK+ C++ compiler and signal handlers

    So, I'm using GTK+ library and GLADE gui constructor, but I'm getting an error when i compile the code in C++, the GTK+ can't find my signal handlers but when i just modify my file names from *.cpp for *.c to codeblocks compile in C, the GTK finds my handlers.
    Other test that i made was put my handler directly in the main file and this didn't work too. Why GTK don't find my handlers?

    Compiler settings:
    Compiler -> other options:
    Code:
    `pkg-config --cflags --libs gtk+-2.0` -export-dynamic
    Linker -> other options:
    Code:
    -export-dynamic
    main.cpp or main.c:
    Code:
    #include <gtk/gtk.h>
    #include "Callbacks.h"
    
    //this handler isn't found in C++
    void on_main_window_destroy(GtkWidget widget, gpointer data_user)
    {
        gtk_main_quit();
    }
    
    int main (int argc, char *argv[])
    {
        GtkBuilder *builder;
        GtkWidget *main_window;
    
        gtk_init(&argc,&argv);
    
        builder = gtk_builder_new();
        gtk_builder_add_from_file(builder,"GUI/main_gui.glade",NULL);
    
        main_window = GTK_WIDGET( gtk_builder_get_object(builder,"main_window"));
        gtk_builder_connect_signals(builder,NULL);
        g_object_unref(G_OBJECT(builder));
    
        gtk_widget_show(main_window);
        gtk_main();
    
        return 0;
    }
    Callbacks.h
    Code:
    #include <gtk/gtk.h>
    
    void on_main_window_destroy(GtkWidget widget, gpointer data_user);
    
    void on_open_menu_activate(GtkWidget widget, gpointer data_user);
    
    void on_save_menu_activate(GtkWidget widget, gpointer data_user);
    
    void on_information_menu_activate(GtkWidget widget, gpointer data_user);
    
    void on_quit_menu_activate(GtkWidget widget, gpointer data_user);
    Callbacks.c or cpp
    Code:
    #include "Callbacks.h"
    
    /*void on_main_window_destroy(GtkWidget widget, gpointer data_user)
    {
        gtk_main_quit(); removed to not duplicate definition(main.cpp)
    }*/
    
    //handlers that aren't found in C++ but are found in C
    void on_quit_menu_activate(GtkWidget widget, gpointer data_user)
    {
        gtk_main_quit();
    }
    
    void on_open_menu_activate(GtkWidget widget, gpointer data_user)
    {
        /*
         ... */
    }
    
    void on_save_menu_activate(GtkWidget widget, gpointer data_user)
    {
    
    }
    
    void on_information_menu_activate(GtkWidget widget, gpointer data_user)
    {
    
    }

  2. #2
    spurious conceit MK27's Avatar
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    And there are no other errors?

    Have you tried using g++ directly?
    C programming resources:
    GNU C Function and Macro Index -- glibc reference manual
    The C Book -- nice online learner guide
    Current ISO draft standard
    CCAN -- new CPAN like open source library repository
    3 (different) GNU debugger tutorials: #1 -- #2 -- #3
    cpwiki -- our wiki on sourceforge

  3. #3
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    Quote Originally Posted by MK27 View Post
    And there are no other errors?

    Have you tried using g++ directly?
    So i tried this command in the terminal:
    Code:
    g++ `pkg-config --cflags --libs gtk+-2.0` -o main  main.cpp Callbacks.cpp
    and got the same error:
    Code:
    (main:2784): Gtk-WARNING **: Could not find signal handler 'on_main_window_destroy'
    
    (main:2784): Gtk-WARNING **: Could not find signal handler 'on_information_menu_activate'
    
    (main:2784): Gtk-WARNING **: Could not find signal handler 'on_quit_menu_activate'
    
    (main:2784): Gtk-WARNING **: Could not find signal handler 'on_save_menu_activate'
    
    (main:2784): Gtk-WARNING **: Could not find signal handler 'on_open_menu_activate'
    Any suggestion?

    Thanks.

  4. #4
    Captain Crash brewbuck's Avatar
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    Portland, OR
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    7,263
    Maybe it's a C++ name mangling problem. Try declaring the signal handlers as extern "C" functions.
    MK27 likes this.
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

  5. #5
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    Quote Originally Posted by brewbuck View Post
    Maybe it's a C++ name mangling problem. Try declaring the signal handlers as extern "C" functions.
    You are a genius, now it works. Thank you very much

  6. #6
    Registered User phylene's Avatar
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    Seattle
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    I wonder if this is the solution to my problem; Linking C++ Static Libs, but I'm confused as to why the linker won't like a c++ app to a c++ static library.

  7. #7
    Registered User
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    for static libraries in C++, they really need to be built with the same compiler as the code in which you're trying to use them. that way you can be (relatively) sure that the names are mangled in the same format. that is what makes it so difficult to use libraries built with G++ in VC++ and vice versa.

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