GTK hello_world memory leak

Question

So ... I'm trying to fix some memory leaks from my GTK + 3 program. Although it would be nice to look at some simple examples to see if there are any cleaning things that I forget, but the hello_world program presented in the documentation also has leaks. (Valgrind output below).

Are these leaks acceptable? If so, is there some other application that I should use to debug GTK programs?

==13717== Memcheck, a memory error detector ==13717== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al. ==13717== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info ==13717== Command: ./a ==13717== Hello World ==13717== ==13717== HEAP SUMMARY: ==13717== in use at exit: 1,578,162 bytes in 11,614 blocks ==13717== total heap usage: 45,699 allocs, 34,085 frees, 6,461,970 bytes allocated ==13717== ==13717== LEAK SUMMARY: ==13717== definitely lost: 2,560 bytes in 5 blocks ==13717== indirectly lost: 6,656 bytes in 207 blocks ==13717== possibly lost: 363,228 bytes in 1,937 blocks ==13717== still reachable: 1,205,718 bytes in 9,465 blocks ==13717== suppressed: 0 bytes in 0 blocks ==13717== Rerun with --leak-check=full to see details of leaked memory ==13717== ==13717== For counts of detected and suppressed errors, rerun with: -v ==13717== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 2 from 2) 

the code:

 #include <gtk/gtk.h> /* This is a callback function. The data arguments are ignored * in this example. More on callbacks below. */ static void print_hello (GtkWidget *widget, gpointer data) { g_print ("Hello World\n"); } static gboolean on_delete_event (GtkWidget *widget, GdkEvent *event, gpointer data) { /* If you return FALSE in the "delete_event" signal handler, * GTK will emit the "destroy" signal. Returning TRUE means * you don't want the window to be destroyed. * * This is useful for popping up 'are you sure you want to quit?' * type dialogs. */ g_print ("delete event occurred\n"); return TRUE; } int main (int argc, char *argv[]) { /* GtkWidget is the storage type for widgets */ GtkWidget *window; GtkWidget *button; /* This is called in all GTK applications. Arguments are parsed * from the command line and are returned to the application. */ gtk_init (&argc, &argv); /* create a new window, and set its title */ window = gtk_window_new (GTK_WINDOW_TOPLEVEL); gtk_window_set_title (GTK_WINDOW (window), "Hello"); /* When the window emits the "delete-event" signal (which is emitted * by GTK+ in response to an event coming from the window manager, * usually as a result of clicking the "close" window control), we * ask it to call the on_delete_event() function as defined above. * * The data passed to the callback function is NULL and is ignored * in the callback function. */ g_signal_connect (window, "delete-event", G_CALLBACK (on_delete_event), NULL); /* Here we connect the "destroy" event to the gtk_main_quit() function. * * This signal is emitted when we call gtk_widget_destroy() on the window, * or if we return FALSE in the "delete_event" callback. */ g_signal_connect (window, "destroy", G_CALLBACK (gtk_main_quit), NULL); /* Sets the border width of the window. */ gtk_container_set_border_width (GTK_CONTAINER (window), 10); /* Creates a new button with the label "Hello World". */ button = gtk_button_new_with_label ("Hello World"); /* When the button receives the "clicked" signal, it will call the * function print_hello() passing it NULL as its argument. * * The print_hello() function is defined above. */ g_signal_connect (button, "clicked", G_CALLBACK (print_hello), NULL); /* The g_signal_connect_swapped() function will connect the "clicked" signal * of the button to the gtk_widget_destroy() function; instead of calling it * using the button as its argument, it will swap it with the user data * argument. This will cause the window to be destroyed by calling * gtk_widget_destroy() on the window. */ g_signal_connect_swapped (button, "clicked", G_CALLBACK (gtk_widget_destroy), window); /* This packs the button into the window. A GtkWindow inherits from GtkBin, * which is a special container that can only have one child */ gtk_container_add (GTK_CONTAINER (window), button); /* The final step is to display this newly created widget... */ gtk_widget_show (button); /* ... and the window */ gtk_widget_show (window); /* All GTK applications must have a gtk_main(). Control ends here * and waits for an event to occur (like a key press or a mouse event), * until gtk_main_quit() is called. */ gtk_main (); return 0; } 

Answer 1

This answer is composed of answers to the same question (on the now defunct www.gtkforums.com).

GTK + is pretty lazy when it comes to allocating and freeing the internal buffers needed for the life of the application. For example, it may allocate memory for the lookup table during initialization, which is necessary for the life of the application. GTK + will never free it. For Valgrind, this looks like a memory leak (which is technically true), but as an optimization, GTK + does not release it, because it will be released when the application exits and, therefore, will not be an error. That's why you need suppression files so that Valgrind can ignore them. The problem is that you will have to change them with most changes to the GTK + version.

Suppression File Repository: https://github.com/dtrebbien/GNOME.supp

After cloning the repository, you can generate suppression files (also supplied with glib, gdk, and others) using "make", and then reference valgrind as follows:

 valgrind ./a --suppression=/path/to/gtk3.supp 

Answer 2

To debug glib / gtk programs, I would use the following command:

 G_SLICE=debug-blocks valgrind --tool=memcheck --leak-check=full <gtk program> 

G_SLICE = debug-blocks will disable gtk extended memory management so that valgrind shows the correct results.

- leak-check = full will show stack traces for missing memory blocks.

You can also use --show-reachable = yes to see stack traces for all memory blocks that were not free when the program exits.

There is also a massif valgrind tool that tracks memory usage to show which parts of the program use the most memory.

Run the program under the array:

 G_SLICE=always-malloc valgrind --tool=massif --detailed-freq=2 --max-snapshots=400 --num-callers=20 <gtk program> 

Show results:

 ms_print massif.out.<pid>