sd_bus_slot_ref - Man Page

#include <systemd/sd-bus​.h>

sd_bus_slot *sd_bus_slot_ref(sd_bus_slot *slot);

sd_bus_slot *sd_bus_slot_unref(sd_bus_slot *slot);

void sd_bus_slot_unrefp(sd_bus_slot **slotp);

sd_bus_slot_ref() increases the internal reference counter of slot by one​.

sd_bus_slot_unref() decreases the internal reference counter of slot by one​. Once the reference count has dropped to zero, slot object is destroyed and cannot be used anymore, so further calls to sd_bus_slot_ref() or sd_bus_slot_unref() are illegal​.

sd_bus_slot_unrefp() is similar to sd_bus_slot_unref() but takes a pointer to a pointer to an sd_bus_slot object​. This call is useful in conjunction with GCC's and LLVM's Clean-up Variable Attribute​^[1]​. See sd_bus_new(3) for an example how to use the cleanup attribute​.

sd_bus_slot_ref() and sd_bus_slot_unref() execute no operation if the passed in bus object address is NULL​. sd_bus_slot_unrefp() will first dereference its argument, which must not be NULL, and will execute no operation if that is NULL​.

sd_bus_slot_ref() always returns the argument​.

sd_bus_slot_unref() always returns NULL​.

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

All functions listed here are thread-agnostic and only a single thread may operate on a given object at any given time​. Different threads may access the same object at different times​. Multiple independent objects may be used from different threads in parallel​.

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 started​.

sd_bus_slot_ref(), sd_bus_slot_unref(), and sd_bus_slot_unrefp() were added in version 240​.

systemd(1), sd-bus(3), sd_bus_new(3), sd_bus_message_new(3), sd_bus_call_method_async(3)

1.

Clean-up Variable Attribute
https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html