NULL values in Gtk{List|Tree}Store ?

[Diego Zuccato <diego otello alma unibo it>]

Hello.

Is it possible to store "null" (SQL-like semantics) values in a
Gtk*Store ?
If yes, how could I test if a cell is "null" ?

Is GValue the answer? If yes, how can I get/set a GValue from a constant
(for example, how do I set "GValue one" to contain the integer "1" ?).
The only two ways I found implies accessing the GValue internals or
using vararg function call...

Tks.

BYtE,
 Diego.