i need help in GTK3 and c ++ my program doesn't want to run

i need help in GTK3 and c ++ my program doesn't want to run

archive main.cpp //------------------------------------

#include "mainWindow.cpp"
int main (int    argc,char **argv)
{

int status;
mainWindow runing;
runing.show();

return status;
}

archive mainWindow.cpp //--------------------------------------

#include <gtk-3.0/gtk/gtk.h>
#include "mainWindow.cpp"

mainWindow::mainWindow(){

GtkApplication *app;
g_signal_connect(app,"show",G_CALLBACK(gtk_main_quit),NULL);
app = gtk_application_new ("org.gtk.example", G_APPLICATION_FLAGS_NONE);
g_object_unref (app);

}

void mainWindow::show() {

gtk_widget_show_all(window);
gtk_window_set_title (GTK_WINDOW (window), "Window");
gtk_window_set_default_size (GTK_WINDOW (window), 200, 200);

}

archive mainWindow.h
// --------------------------------------
#include <gtk-3.0/gtk/gtk.h>
class mainWindow {
   public:
       mainWindow();
       void show();

 private:
   GtkWidget *window;
};

**why my application does not run I am programming in Clion**