diff --git a/man/sd_bus_error.xml b/man/sd_bus_error.xml index bfc5caf4e2..bb8015de5e 100644 --- a/man/sd_bus_error.xml +++ b/man/sd_bus_error.xml @@ -147,55 +147,54 @@ Description - The sd_bus_error structure carries - information about a D-Bus error condition. 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. Set an error - structure to SD_BUS_ERROR_NULL in order to - reset both fields to NULL. When no longer necessary, resources - held by the sd_bus_error structure should - be destroyed with sd_bus_error_free(). + 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. - 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 error structure again when it is not - required anymore (see above). The function will return an - errno-like negative value (see 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. 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. If - e is NULL, no error structure is initialized, - but the error is still converted into an - errno-style error. If - name is NULL, it is - assumed that no error occurred, and 0 is returned. This means that - this function may 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 might be set - instead and -ENOMEM be returned. Do not use this call on error - structures that are already initialized. If you intend to reuse an - error structure, free the old data stored in it with - sd_bus_error_free() first. + 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 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() can, 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(), 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 set - name from an - errno-like value that is converted to a D-Bus + 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. The absolute value - is used implicitly. 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. + project='die-net'>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 @@ -246,28 +237,26 @@ project='man-pages'>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_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 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. + 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 - (or NULL) dst is initializated 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, negative error code. + 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 initializated 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 @@ -300,25 +289,23 @@ Return Value - The functions sd_bus_error_set(), - sd_bus_error_setf(), and - sd_bus_error_set_const(), when successful, - return the negative errno value corresponding to the - name parameter. The functions - sd_bus_error_set_errno(), - sd_bus_error_set_errnof() and - sd_bus_error_set_errnofv(), when successful, - return the negative value of the error - parameter. If an error occurs, one of the negative error values - listed below will be returned. + 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 0 or a positive - integer on success, and a negative error value converted from the error 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 diff --git a/src/libsystemd/sd-bus/bus-error.c b/src/libsystemd/sd-bus/bus-error.c index df292fe3d5..7747600b83 100644 --- a/src/libsystemd/sd-bus/bus-error.c +++ b/src/libsystemd/sd-bus/bus-error.c @@ -465,7 +465,7 @@ _public_ int sd_bus_error_set_errno(sd_bus_error *e, int error) { if (!e) return -error; if (error == 0) - return -error; + return 0; assert_return(!bus_error_is_dirty(e), -EINVAL);