[libvirt] [PATCH 7/8] examples: Use G_N_ELEMENTS instead of ARRAY_CARDINALITY

[Andrea Bolognani]

On Tue, 2019-10-15 at 18:21 +0100, Daniel P. Berrangé wrote:
> On Tue, Oct 15, 2019 at 04:10:55PM +0200, Andrea Bolognani wrote:
> > On Tue, 2019-10-15 at 14:21 +0200, Ján Tomko wrote:
> > > -#define ARRAY_CARDINALITY(Array) (sizeof(Array) / sizeof(*(Array)))
> > > +#define G_N_ELEMENTS(Array) (sizeof(Array) / sizeof(*(Array)))
> > 
> > In this case, and in this case only, I think we should leave the name
> > alone.
> > 
> > When we use GLib and simply provide our own implementation when using
> > a version that's too old, the GLib name is obviously accurate, but in
> > this specific case I think it's misleading and we should stick with
> > the current one.
> 
> We do have the option to have our example programs use GLib instead
> of plain C. If people are using libvirt from plain C, I'm inclined
> to suggest they'd be wise to use GLib for the same reasons that it
> is beneficial for libvirt to use GLib.
> 
> If they're not using GLib, they likely have enough C knowledge to
> figure out what they must do from our examples anyway.

Introducing a dependency on GLib for the example sounds acceptable
to me, and certainly better than defining G_* macros ourselves.

One thing we could do, and which would be useful in general as well
as being fairly common from what I've seen in other projects, is to
have a comment at the start of the example file along the lines of

  /* event-test - listen to libvirt events
   *
   * Compile with:
   *
   *   gcc -o event-test event-test.c \
   *     $(pkg-config --cflags --libs libvirt glib-2.0)
   */

At that point even people who are not that familiar with C, libvirt
or GLib will be able to build and run the example.

-- 
Andrea Bolognani / Red Hat / Virtualization