sd_bus_error
systemd
sd_bus_error
3
sd_bus_error
SD_BUS_ERROR_MAKE_CONST
SD_BUS_ERROR_NULL
sd_bus_error_free
sd_bus_error_set
sd_bus_error_setf
sd_bus_error_set_const
sd_bus_error_set_errno
sd_bus_error_set_errnof
sd_bus_error_set_errnofv
sd_bus_error_get_errno
sd_bus_error_copy
sd_bus_error_move
sd_bus_error_is_set
sd_bus_error_has_name
sd_bus_error_has_names_sentinel
sd_bus_error_has_names
sd-bus error handling
#include <systemd/sd-bus.h>
typedef struct {
const char *name;
const char *message;
…
} sd_bus_error;
SD_BUS_ERROR_MAKE_CONST(name, message)
SD_BUS_ERROR_NULL
void sd_bus_error_free
sd_bus_error *e
int sd_bus_error_set
sd_bus_error *e
const char *name
const char *message
int sd_bus_error_setf
sd_bus_error *e
const char *name
const char *format
…
int sd_bus_error_set_const
sd_bus_error *e
const char *name
const char *message
int sd_bus_error_set_errno
sd_bus_error *e
int error
int sd_bus_error_set_errnof
sd_bus_error *e
int error
const char *format
…
int sd_bus_error_set_errnofv
sd_bus_error *e
int error
const char *format
va_list ap
int sd_bus_error_get_errno
const sd_bus_error *e
int sd_bus_error_copy
sd_bus_error *dst
const sd_bus_error *e
int sd_bus_error_move
sd_bus_error *dst
sd_bus_error *e
int sd_bus_error_is_set
const sd_bus_error *e
int sd_bus_error_has_name
const sd_bus_error *e
const char *name
int sd_bus_error_has_names_sentinel
const sd_bus_error *e
...
#define sd_bus_error_has_names(e, ...) sd_bus_error_has_names_sentinel(e, ..., NULL)
Description
The sd_bus_error structure carries information about a D-Bus error
condition, or lack thereof. The functions described below may be used to set and query fields in this
structure.
The name field contains a short identifier of an error. It
should follow the rules for error names described in the D-Bus specification, subsection Valid
Names. A number of common, standardized error names are described in
sd-bus-errors3, but
additional domain-specific errors may be defined by applications.
The message field usually contains a human-readable string
describing the details, but might be NULL.
An unset sd_bus_error structure should have both fields initialized to
NULL, and signifies lack of an error, i.e. success. Assign
SD_BUS_ERROR_NULL to the structure in order to initialize both fields to
NULL. When no longer necessary, resources held by the
sd_bus_error structure should be destroyed with
sd_bus_error_free().
sd_bus_error_set() sets an error structure to the specified name and message
strings. The strings will be copied into internal, newly allocated memory. It is essential to free the
contents again when they are not required anymore (see above). Do not use this call on error structures
that have already been set. If you intend to reuse an error structure, free the old data stored in it
with sd_bus_error_free() first.
sd_bus_error_set() will return an errno-like value (see
errno3)
determined from the specified error name name. If name is
NULL, it is assumed that no error occurred, and 0 is returned.
If name is nonnull, a negative value is always returned. If
e is NULL, no error structure is initialized, but
name is still converted into an errno-style value.
Various well-known D-Bus errors are converted to well-known errno counterparts,
and the other ones to -EIO. See
sd-bus-errors3 for a
list of well-known error names. Additional error mappings may be defined with
sd_bus_error_add_map3.
sd_bus_error_set() is designed to be conveniently used in a
return statement. If message is NULL, no
message is set. This call can fail if no memory may be allocated for the name and message strings, in
which case an SD_BUS_ERROR_NO_MEMORY error will be set instead and
-ENOMEM returned.
sd_bus_error_setf() is similar to
sd_bus_error_set(), but takes a printf3
format string and corresponding arguments to generate the
message field.
sd_bus_error_set_const() is similar to
sd_bus_error_set(), but the string parameters are not copied internally, and must
hence remain constant and valid for the lifetime of e. Use this call to avoid
memory allocations when setting error structures. Since this call does not allocate memory, it will not
fail with an out-of-memory condition as sd_bus_error_set() may, as described
above. Alternatively, the SD_BUS_ERROR_MAKE_CONST() macro may be used to generate a
literal, constant bus error structure on-the-fly.
sd_bus_error_set_errno() will immediately return 0 if the
specified error parameter error is 0. Otherwise, it will set
name from an errno-like value that is converted to a D-Bus
error. strerror_r3 will
be used to set message. Well-known D-Bus error names will be used for
name if applicable, otherwise a name in the System.Error.
namespace will be generated. The sign of the specified error number is ignored and the absolute value is
used implicitly. If the specified error error is non-zero, the call always returns
a negative value, for convenient usage in return statements. This call might fail
due to lack of memory, in which case an SD_BUS_ERROR_NO_MEMORY error is set instead,
and -ENOMEM is returned.
sd_bus_error_set_errnof() is similar to
sd_bus_error_set_errno(), but in addition to
error, takes a printf3
format string and corresponding arguments. The
message field will be generated from
format and the arguments.
sd_bus_error_set_errnofv() is similar to
sd_bus_error_set_errnof(), but takes the
format string parameters as va_arg3
parameter list.
sd_bus_error_get_errno() converts the name field of
an error structure to an errno-like (positive) value using the same rules as
sd_bus_error_set(). If e is NULL,
0 will be returned.
sd_bus_error_copy() will initialize dst using the
values in e, if e has been set with an error value before.
Otherwise, it will return immediately. If the strings in e were set using
sd_bus_error_set_const(), they will be shared. Otherwise, they will be
copied. Returns a converted errno-like, negative error code or 0.
Before this call, dst must be unset, i.e. either freshly initialized with
NULL or reset using sd_bus_error_free().
sd_bus_error_move() is similar to sd_bus_error_copy(),
but will move any error information from e into dst,
resetting the former. This function cannot fail, as no new memory is allocated. Note that if
e is not set, dst is initialized to
SD_BUS_ERROR_NULL. Moreover, if dst is
NULL no operation is executed on it and resources held by e
are freed and reset. Returns a converted errno-like, non-positive error value.
sd_bus_error_is_set() will return a
non-zero value if e is
non-NULL and an error has been set,
false otherwise.
sd_bus_error_has_name() will return a
non-zero value if e is
non-NULL and an error with the same
name has been set,
false otherwise.
sd_bus_error_has_names_sentinel() is similar to
sd_bus_error_has_name(), but takes multiple names to check against. The list must be
terminated with NULL. sd_bus_error_has_names()
is a macro wrapper around sd_bus_error_has_names_sentinel() that adds the
NULL sentinel automatically.
sd_bus_error_free() will destroy
resources held by e. The parameter itself
will not be deallocated, and must be free3d
by the caller if necessary. The function may also be called safely
on unset errors (error structures with both fields set to NULL),
in which case it performs no operation. This call will reset the
error structure after freeing the data, so that all fields are set
to NULL. The structure may be reused afterwards.
Return Value
The functions sd_bus_error_set(), sd_bus_error_setf(),
and sd_bus_error_set_const() always return 0 when the specified
error value is NULL, and a negative errno-like value corresponding to the
name parameter otherwise. The functions
sd_bus_error_set_errno(), sd_bus_error_set_errnof() and
sd_bus_error_set_errnofv(), return 0 when the specified error
value is 0, and a a negative errno-like value corresponding to the
error parameter otherwise. If an error occurs internally, one of the negative
error values listed below will be returned.
sd_bus_error_get_errno() returns
false when e is
NULL, and a positive errno value mapped from
e->name otherwise.
sd_bus_error_copy() and sd_bus_error_move() return a
negative error value converted from the source error, and zero if the error has not been set.
sd_bus_error_is_set() returns a
non-zero value when e and the
name field are
non-NULL, zero otherwise.
sd_bus_error_has_name(), sd_bus_error_has_names(), and
sd_bus_error_has_names_sentinel() return a non-zero value when e is
non-NULL and the name field is equal to one of the given
names, zero otherwise.
Reference ownership
sd_bus_error is not reference
counted. Users should destroy resources held by it by calling
sd_bus_error_free(). Usually, error structures
are allocated on the stack or passed in as function parameters,
but they may also be allocated dynamically, in which case it is
the duty of the caller to free3
the memory held by the structure itself after freeing its contents
with sd_bus_error_free().
Errors
Returned errors may indicate the following problems:
-EINVAL
Error was already set in sd_bus_error structure when one
the error-setting functions was called.
-ENOMEM
Memory allocation failed.
See Also
systemd1,
sd-bus3,
sd-bus-errors3,
sd_bus_error_add_map3,
errno3,
strerror_r3