Valgrind is a programmer tool that allows to track memory related errors in C and C++ programs.
You can read a full introduction on the Valgrind website.
This page includes some tips on how to proficiently use valgrind on GTK/GNOME programs. Feel free to add your own tricks or expand the page with more detailed explanations.
Memcheck is the main valgrind tool, it allows to detect memory leaks and other memory management errors. To run a gnome program under memcheck run:
valgrind \ --leak-check=full \ --num-callers=20 \ --log-file=vgdump.txt\ your-program
If the program you are debugging uses dynamically loaded modules with
GModule (for instance it has a
GModule based plugin system) you should
G_DEBUG=resident-modules to make sure that the modules do not get
unloaded and valgrind can retrieve the function names when writing its log:
G_DEBUG=resident-modules valgrind \ --leak-check=full \ --num-callers=20 \ --log-file=vgdump.txt \ your-program
If you are still using Autotools as your build system, your binary is really
a libtool-generated temporary wrapper, the above command line will run
valgrind on your shell which is probably not what you want. You will need to
libtool --mode=execute valgrind ... instead.
After running the program you can inspect the log in the vgdump file. The log
contains a list of memory related issues and in particular memory leaks. Memory
leaks are marked in three ways: definitely lost, possibly lost and still
reachable. For a start, concentrate on the definitely lost ones, which are bits
of memory leaked for sure—you can filter for them by passing
--show-leak-kinds=definite. For each leak valgrind provides a backtrace which
lets you pinpoint exactly where the leaks happens, in particular if your program
was compiled with debugging symbols, valgrind will tell you the exact line and
file of the leak.
GLib and other libraries often make one-off allocations that are meant to exist until the end of the lifetime of your application. These are not leaks, but Valgrind will mark them as such. In order to avoid cluttering your reports, you can use “suppression files”, to tell Valgrind to eliminate known one-off allocations. GLib and GTK provide suppression files that you can use.
Assuming your copy of GLib and GTK are installed under
/usr, the Valgrind
suppression files are located here:
You can use them with the
--suppressions argument for the memcheck tool, e.g.:
valgrind \ --suppressions=/usr/share/glib-2.0/valgrind/glib.supp \ --suppressions=/usr/share/gtk-4.0/valgrind/gtk.supp \ your-gtk-app
You can use multiple
--suppressions arguments, one for each suppression
If your project has its own one-off allocations you wish to suppress, you can write your own suppression file by following the instructions in the Valgrind documentation.