Error reporting for dbus

劉大俠GG_B發表於2020-06-11

D-Bus 1.13.14

Error reporting

Error reporting. More...

Data Structures
struct	DBusError
	Object representing an exception. More...

Typedefs
typedef struct DBusError	DBusError
	Mostly-opaque type representing an error that occurred.

Functions
void	dbus_error_init (DBusError *error)
	Initializes a DBusError structure. More...

void	dbus_error_free (DBusError *error)
	Frees an error that's been set (or just initialized), then reinitializes the error as in dbus_error_init(). More...

void	dbus_set_error_const (DBusError error, const char name, const char *message)
	Assigns an error name and message to a DBusError. More...

void	dbus_move_error (DBusError src, DBusError dest)
	Moves an error src into dest, freeing src and overwriting dest. More...

dbus_bool_t	dbus_error_has_name (const DBusError error, const char name)
	Checks whether the error is set and has the given name. More...

dbus_bool_t	dbus_error_is_set (const DBusError *error)
	Checks whether an error occurred (the error is set). More...

void	dbus_set_error (DBusError error, const char name, const char *format,...)
	Assigns an error name and message to a DBusError. More...

void	_dbus_set_error_valist (DBusError error, const char name, const char *format, va_list args)

Detailed Description

Error reporting.

Types and functions related to reporting errors.

In essence D-Bus error reporting works as follows:

DBusError error;

dbus_error_init (&error);

dbus_some_function (arg1, arg2, &error);

if (dbus_error_is_set (&error))

{

fprintf (stderr, "an error occurred: %s\n", error.message);

dbus_error_free (&error);

}

By convention, all functions allow NULL instead of a DBusError*, so callers who don't care about the error can ignore it.

There are some rules. An error passed to a D-Bus function must always be unset; you can't pass in an error that's already set. If a function has a return code indicating whether an error occurred, and also a DBusError parameter, then the error will always be set if and only if the return code indicates an error occurred. i.e. the return code and the error are never going to disagree.

An error only needs to be freed if it's been set, not if it's merely been initialized.

You can check the specific error that occurred using dbus_error_has_name().

Errors will not be set for programming errors, such as passing invalid arguments to the libdbus API. Instead, libdbus will print warnings, exit on a failed assertion, or even crash in those cases (in other words, incorrect use of the API results in undefined behavior, possibly accompanied by helpful debugging output if you're lucky).

Function Documentation

◆ dbus_error_free()

DBUS_EXPORT void dbus_error_free	(	DBusError *	error	)

Frees an error that's been set (or just initialized), then reinitializes the error as in dbus_error_init().

Parameters

errormemory where the error is stored.

Definition at line 211 of file dbus-errors.c.

References DBusRealError::const_message, dbus_error_init(), dbus_free(), DBusRealError::message, DBusRealError::name, and NULL.

Referenced by _dbus_generate_uuid(), _dbus_read_local_machine_uuid(), dbus_get_local_machine_id(), and dbus_move_error().

◆ dbus_error_has_name()

DBUS_EXPORT dbus_bool_t dbus_error_has_name	(	const DBusError *	error,
		const char *	name
	)

Checks whether the error is set and has the given name.

Parameters

errorthe error namethe name
Returns

TRUE if the given named error occurred

Definition at line 302 of file dbus-errors.c.

References _dbus_assert, _dbus_string_equal(), _dbus_string_init_const(), FALSE, DBusError::message, DBusError::name, and NULL.

Referenced by dbus_get_local_machine_id().

◆ dbus_error_init()

DBUS_EXPORT void dbus_error_init	(	DBusError *	error	)

Initializes a DBusError structure.

Does not allocate any memory; the error only needs to be freed if it is set at some point.

Parameters

errorthe DBusError.

Definition at line 188 of file dbus-errors.c.

Referenced by _dbus_generate_uuid(), _dbus_listen_tcp_socket(), dbus_error_free(), and dbus_move_error().

◆ dbus_error_is_set()

DBUS_EXPORT dbus_bool_t dbus_error_is_set	(	const DBusError *	error	)

Checks whether an error occurred (the error is set).

Parameters

errorthe error object
Returns

TRUE if an error occurred

Definition at line 329 of file dbus-errors.c.

References _dbus_assert, FALSE, DBusError::message, DBusError::name, and NULL.

◆ dbus_move_error()

DBUS_EXPORT void dbus_move_error	(	DBusError *	src,
		DBusError *	dest
	)

Moves an error src into dest, freeing src and overwriting dest.

Both src and dest must be initialized. src is reinitialized to an empty error. dest may not contain an existing error. If the destination is NULL, just frees and reinits the source error.

Parameters

srcthe source error destthe destination error or NULL

Definition at line 279 of file dbus-errors.c.

References dbus_error_free(), and dbus_error_init().

◆ dbus_set_error()

(	DBusError *	error,
	const char *	name,
	const char *	format,
		...
)

Assigns an error name and message to a DBusError.

Does nothing if error is NULL.

The format may be NULL, which means a (pretty much useless) default message will be deduced from the name. This is not a good idea, just go ahead and provide a useful error message. It won't hurt you.

If no memory can be allocated for the error message, an out-of-memory error message will be set instead.

Parameters

errorthe error.or NULL namethe error name formatprintf-style format string.

Definition at line 354 of file dbus-errors.c.

References NULL.

Referenced by _dbus_babysitter_set_child_exit_error(), _dbus_become_daemon(), _dbus_change_to_daemon_user(), _dbus_check_dir_is_private_to_user(), _dbus_close(), _dbus_close_socket(), _dbus_command_for_pid(), _dbus_connect_exec(), _dbus_create_directory(), _dbus_create_file_exclusively(), _dbus_delete_directory(), _dbus_delete_file(), _dbus_directory_get_next_file(), _dbus_directory_open(), _dbus_dup(), _dbus_ensure_directory(), _dbus_file_get_contents(), _dbus_generate_random_bytes(), _dbus_generate_uuid(), _dbus_is_console_user(), _dbus_keyring_new_for_credentials(), _dbus_listen_systemd_sockets(), _dbus_listen_tcp_socket(), _dbus_lookup_launchd_socket(), _dbus_make_file_world_readable(), _dbus_message_iter_get_args_valist(), _dbus_read_local_machine_uuid(), _dbus_send_credentials_socket(), _dbus_server_listen_platform_specific(), _dbus_server_new_for_domain_socket(), _dbus_server_new_for_launchd(), _dbus_server_new_for_tcp_socket(), _dbus_set_bad_address(), _dbus_set_socket_nonblocking(), _dbus_socketpair(), _dbus_stat(), _dbus_string_save_to_file(), _dbus_transport_new_for_tcp_socket(), _dbus_transport_open_platform_specific(), _dbus_unix_user_is_at_console(), _dbus_user_database_lookup(), _dbus_user_database_lookup_group(), dbus_connection_send_with_reply_and_block(), dbus_message_demarshal(), dbus_parse_address(), dbus_set_error_from_message(), dbus_signature_validate(), dbus_signature_validate_single(), dbus_try_get_local_machine_id(), dbus_validate_bus_name(), dbus_validate_error_name(), dbus_validate_interface(), dbus_validate_member(), dbus_validate_path(), and dbus_validate_utf8().

◆ dbus_set_error_const()

(	DBusError *	error,
	const char *	name,
	const char *	message
)

Assigns an error name and message to a DBusError.

Does nothing if error is NULL. The message may be NULL, which means a default message will be deduced from the name. The default message will be totally useless, though, so using a NULL message is not recommended.

Because this function does not copy the error name or message, you must ensure the name and message are global data that won't be freed. You probably want dbus_set_error() instead, in most cases.