gtk_combo_box_get_active_text fails ???

[Olivier <Olivier Ramare univ-lille1 fr>]

Dear all,

  here is part of my code:
-------------------------------
    my_combox_box = gtk_combo_box_new_text();
    g_signal_connect (my_combox_box, "changed",
                      G_CALLBACK (select), NULL);

and
void select(GtkComboBox *combo)
{
    char *name = NULL; /* or gchar, it is the same */

    name = PTALLOC(char);
    if (gtk_combo_box_get_active_text (combo) == NULL){
        printf("What are we doing in here ???");
    } else {
        name = gtk_combo_box_get_active_text (combo);
        ....;};
}
-------------------------------

Any call to "select" ends in Segmentation fault ...
One full day that I'm looking at that :-(
Any help appreciated :-)
Best,
Amities,
          Olivier