sd_bus_slot_set_floating(3) — Linux manual page


SD_BUS_S...FLOATING(3)  sd_bus_slot_set_floating  SD_BUS_S...FLOATING(3)

NAME         top

       sd_bus_slot_set_floating, sd_bus_slot_get_floating - Control
       whether a bus slot object is "floating"

SYNOPSIS         top

       #include <systemd/sd-bus.h>

       int sd_bus_slot_set_floating(sd_bus_slot *slot, int b);

       int sd_bus_slot_get_floating(sd_bus_slot *slot);

DESCRIPTION         top

       sd_bus_slot_set_floating() controls whether the specified bus
       slot object slot shall be "floating" or not. A floating bus slot
       object's lifetime is bound to the lifetime of the bus object it
       is associated with, meaning that it remains allocated as long as
       the bus object itself and is freed automatically when the bus
       object is freed. Regular (i.e. non-floating) bus slot objects
       keep the bus referenced, hence the bus object remains allocated
       at least as long as there remains at least one referenced bus
       slot object around. The floating state hence controls the
       direction of referencing between the bus object and the bus slot
       objects: if floating the bus pins the bus slot, and otherwise the
       bus slot pins the bus objects. Use sd_bus_slot_set_floating() to
       switch between both modes: if the b parameter is zero, the slot
       object is considered floating, otherwise it is made a regular
       (non-floating) slot object.

       Bus slot objects may be allocated with calls such as
       sd_bus_add_match(3). If the slot of these functions is non-NULL
       the slot object will be of the regular kind (i.e. non-floating),
       otherwise it will be created floating. With
       sd_bus_slot_set_floating() a bus slot object allocated as regular
       can be converted into a floating object and back. This is
       particularly useful for creating a bus slot object, then changing
       parameters of it, and then turning it into a floating object,
       whose lifecycle is managed by the bus object.

       sd_bus_slot_get_floating() returns the current floating state of
       the specified bus slot object. It returns negative on error, zero
       if the bus slot object is a regular (non-floating) object and
       positive otherwise.

RETURN VALUE         top

       On success, these functions return 0 or a positive integer. On
       failure, they return a negative errno-style error code.

       Returned errors may indicate the following problems:

           The slot parameter is NULL.

           The bus connection has been created in a different process,
           library or module instance.

           The bus object the specified bus slot object is associated
           with has already been freed, and hence no change in the
           floating state can be made anymore.

NOTES         top

       Functions described here are available as a shared library, which
       can be compiled against and linked to with the
       libsystemd pkg-config(1) file.

       The code described here uses getenv(3), which is declared to be
       not multi-thread-safe. This means that the code calling the
       functions described here must not call setenv(3) from a parallel
       thread. It is recommended to only do calls to setenv() from an
       early phase of the program when no other threads have been

HISTORY         top

       sd_bus_slot_set_floating() and sd_bus_slot_get_floating() were
       added in version 239.

SEE ALSO         top

       systemd(1), sd-bus(3), sd_bus_slot_set_destroy_callback(3),

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨⟩.  If you have
       a bug report for this manual page, see
       This page was obtained from the project's upstream Git repository
       ⟨⟩ on 2023-12-22.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2023-12-22.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there
       is a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to

systemd 255                                       SD_BUS_S...FLOATING(3)

Pages that refer to this page: sd-bus(3)sd_bus_add_match(3)sd_bus_add_node_enumerator(3)sd_bus_add_object(3)sd_bus_add_object_manager(3)sd_bus_call(3)sd_bus_default(3)sd_bus_slot_set_destroy_callback(3)systemd.directives(7)systemd.index(7)