sd_bus_message_new, sd_bus_message_ref, sd_bus_message_unref,
SD_BUS_MESSAGE_SIGNAL, sd_bus_message_get_bus - Create a new bus
message object and create or destroy references to it
sd_bus_message_new() creates a new bus message object attached to the
bus bus and returns it in the output parameter m. This object is
reference-counted, and will be destroyed when all references are
gone. Initially, the caller of this function owns the sole reference
to the message object. Note that the message object holds a reference
to the bus object, so the bus object will not be destroyed as long as
the message exists.
Note: this is a low-level call. In most cases functions like
sd_bus_message_new_method_return(3), and sd_bus_message_new_signal(3)
that create a message of a certain type and initialize various fields
are easier to use.
The type parameter specifies the type of the message. It must be one
of SD_BUS_MESSAGE_METHOD_CALL — a method call,
SD_BUS_MESSAGE_METHOD_RETURN — a method call reply,
SD_BUS_MESSAGE_METHOD_ERROR — an error reply to a method call,
SD_BUS_MESSAGE_SIGNAL — a broadcast message with no reply.
The flag to allow interactive authorization is initialized based on
the current value set in the bus object, see
sd_bus_set_allow_interactive_authorization(3). This may be changed
sd_bus_message_ref() increases the reference counter of m by one.
sd_bus_message_unref() decreases the reference counter of m by one.
Once the reference count has dropped to zero, message object is
destroyed and cannot be used anymore, so further calls to
sd_bus_message_ref() or sd_bus_message_unref() are illegal.
sd_bus_message_unrefp() is similar to sd_bus_message_unref() but
takes a pointer to a pointer to an sd_bus_message object. This call
is useful in conjunction with GCC's and LLVM's Clean-up VariableAttribute. See sd_bus_new(3) for an example how to use the cleanup
sd_bus_message_ref() and sd_bus_message_unref() execute no operation
if the passed in bus object address is NULL. sd_bus_message_unrefp()
will first dereference its argument, which must not be NULL, and will
execute no operation if that is NULL.
sd_bus_message_get_bus() returns the bus object that message m is
On success, sd_bus_message_new() returns 0 or a positive integer. On
failure, it returns a negative errno-style error code.
sd_bus_message_ref() always returns the argument.
sd_bus_message_unref() always returns NULL.
sd_bus_message_get_bus() always returns the bus object.
Returned errors may indicate the following problems:
Specified type is invalid.
The bus parameter bus is NULL or the bus is not connected.
Memory allocation failed.
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systemd 246 SD_BUS_MESSAGE_NEW(3)