Re: g_intern_static_string() for type names as small optimization

["Matthias Clasen" <matthias clasen gmail com>]

On Jan 16, 2008 11:24 AM, Andrew W. Nosenko <andrew w nosenko gmail com> wrote:

>
> I'm asking not about general benefits of an intern strings or GQuarks
> (which are backend of Glib's intern strings), but about benefits, which
> expected by GTK/Glib developers, for constructs like (please, pay
> attention on the 2nd parameter of the g_type_register_static())
>
>         type_module_type = g_type_register_static (G_TYPE_OBJECT,
>                                                 g_intern_static_string ("GTypeModule"),
>                                                 /* ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ */
>                                                 &type_module_info,
>                                                 G_TYPE_FLAG_ABSTRACT);
>
> in comparison with using of the "plain" 'const char*' string in the same
> context:
>
>         type_module_type = g_type_register_static (G_TYPE_OBJECT,
>                                                 "GTypeModule",
>                                                 /* ^^^^^^^^^^ */
>                                                 &type_module_info,
>                                                 G_TYPE_FLAG_ABSTRACT);
>
> because underlying machinery of the g_type_register_static() cannot
> assume that 'type_name' parameter is interned and, therefore, either
> should use strcmp() all the times (don't belive, but...), or (more
> probable) just to convert it to GQuark or intern string again by self.
>
> Therefore a question: what win/profit/optimization gives this early
> interning?
>

The thing is that GObject interns the type name anyway. But, as you say,
it cannot assume that the string is static and thus calls g_intern_string(),
causing it to be copied. By interning it using
g_intern_static_string() beforehand,
we guarantee that the string is already interned at the time that gobject calls
g_intern_string, and thus won't be copied.

As I said, it is a pretty small optimization...