- <para><function>sd_bus_slot_set_destroy_callback()</function> sets
- <parameter>callback</parameter> as the callback function to be called right before the bus slot
- object <parameter>slot</parameter> is deallocated. The <parameter>userdata</parameter> pointer
- from the slot object will be passed as the <parameter>userdata</parameter> parameter. This
- pointer can be set specified as an argument to the constuctor functions, see
- <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- or directly, see
- <citerefentry><refentrytitle>sd_bus_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
- This callback function is called even if <parameter>userdata</parameter> is
- <constant>NULL</constant>.</para>
+ <para><function>sd_bus_slot_set_destroy_callback()</function> sets <parameter>callback</parameter> as the callback
+ function to be called right before the bus slot object <parameter>slot</parameter> is deallocated. The
+ <parameter>userdata</parameter> pointer from the slot object will be passed as the <parameter>userdata</parameter>
+ parameter. This pointer can be set by an argument to the constructor functions, see
+ <citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>, or directly,
+ see <citerefentry><refentrytitle>sd_bus_slot_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
+ This callback function is called even if <parameter>userdata</parameter> is <constant>NULL</constant>. Note that
+ this callback is invoked at a time where the bus slot object itself is already invalidated, and executing
+ operations or taking new references to the bus slot object is not permissible.</para>