With the following sequence (which we're doing in some long-standing this-used-to-work unit tests) the following code crashes GTK 3.4.2

    gtk_entry_set_icon_pixbuf(entry, GTK_ENTRY_ICON_PRIMARY, NULL);
    gtk_entry_get_icon_pixbuf(entry);

should return NULL, but is crashing with G_IS_OBJECT() failing inside g_object_unref(). I checked out that tag from git and the line in question was 7940 of gtk/gtkentry.c:

    /* HACK: unfortunately this is transfer none, so we need to return
     * the icon helper's cache ref directly.
     */
    pixbuf = gtk_entry_ensure_pixbuf (entry, icon_pos);
    g_object_unref (pixbuf);

This code is unchanged in master; the unref is now at line 7949 in gtk/gtkentry.c.

With a comment like that, I'm guessing that something to do the the returned pixbuf not being what it should be, but I'm surprised at g_object_unref() CRITICAL'ing.

Backtrace follows, not that it really matters.

AfC