diff options
| -rw-r--r-- | man/sd_bus_error.xml | 205 | ||||
| -rw-r--r-- | src/libsystemd/sd-bus/bus-error.c | 2 |
2 files changed, 97 insertions, 110 deletions
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 @@ <refsect1> <title>Description</title> - <para>The <structname>sd_bus_error</structname> 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 - <structfield>name</structfield> field contains a short identifier - of an error. It should follow the rules for error names described - in the D-Bus specification, subsection <ulink - url="http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names">Valid - Names</ulink>. A number of common, standardized error names are - described in - <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>, - but additional domain-specific errors may be defined by - applications. The <structfield>message</structfield> field usually - contains a human-readable string describing the details, but might - be <constant>NULL</constant>. An unset <structname>sd_bus_error</structname> structure - should have both fields initialized to <constant>NULL</constant>. Set an error - structure to <constant>SD_BUS_ERROR_NULL</constant> in order to - reset both fields to <constant>NULL</constant>. When no longer necessary, resources - held by the <structname>sd_bus_error</structname> structure should - be destroyed with <function>sd_bus_error_free()</function>.</para> - - <para><function>sd_bus_error_set()</function> 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 - <varname>errno</varname>-like negative value (see <citerefentry + <para>The <structname>sd_bus_error</structname> 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. + <itemizedlist> + <listitem><para>The <structfield>name</structfield> field contains a short identifier of an error. It + should follow the rules for error names described in the D-Bus specification, subsection <ulink + url="http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names">Valid + Names</ulink>. A number of common, standardized error names are described in + <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>, but + additional domain-specific errors may be defined by applications.</para></listitem> + + <listitem><para>The <structfield>message</structfield> field usually contains a human-readable string + describing the details, but might be <constant>NULL</constant>.</para></listitem> + </itemizedlist> + An unset <structname>sd_bus_error</structname> structure should have both fields initialized to + <constant>NULL</constant>, and signifies lack of an error, i.e. success. Assign + <constant>SD_BUS_ERROR_NULL</constant> to the structure in order to initialize both fields to + <constant>NULL</constant>. When no longer necessary, resources held by the + <structname>sd_bus_error</structname> structure should be destroyed with + <function>sd_bus_error_free()</function>.</para> + + <para><function>sd_bus_error_set()</function> 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 <function>sd_bus_error_free()</function> first.</para> + + <para><function>sd_bus_error_set()</function> will return an <varname>errno</varname>-like value (see + <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>) - determined from the specified error name. Various well-known - D-Bus errors are converted to well-known <varname>errno</varname> - counterparts, and the other ones to <constant>-EIO</constant>. See - <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry> - for a list of well-known error names. Additional error mappings - may be defined with - <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If - <parameter>e</parameter> is <constant>NULL</constant>, no error structure is initialized, - but the error is still converted into an - <varname>errno</varname>-style error. If - <parameter>name</parameter> is <constant>NULL</constant>, it is - assumed that no error occurred, and 0 is returned. This means that - this function may be conveniently used in a - <function>return</function> statement. If - <parameter>message</parameter> is <constant>NULL</constant>, no message is set. This - call can fail if no memory may be allocated for the name and - message strings, in which case an - <constant>SD_BUS_ERROR_NO_MEMORY</constant> 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 - <function>sd_bus_error_free()</function> first.</para> + determined from the specified error name <parameter>name</parameter>. If <parameter>name</parameter> is + <constant>NULL</constant>, it is assumed that no error occurred, and <constant>0</constant> is returned. + If <parameter>name</parameter> is nonnull, a negative value is always returned. If + <parameter>e</parameter> is <constant>NULL</constant>, no error structure is initialized, but + <parameter>name</parameter> is still converted into an <varname>errno</varname>-style value.</para> + + <para>Various well-known D-Bus errors are converted to well-known <varname>errno</varname> counterparts, + and the other ones to <constant>-EIO</constant>. See + <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry> for a + list of well-known error names. Additional error mappings may be defined with + <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>. + </para> + + <para><function>sd_bus_error_set()</function> is designed to be conveniently used in a + <function>return</function> statement. If <parameter>message</parameter> is <constant>NULL</constant>, no + message is set. This call can fail if no memory may be allocated for the name and message strings, in + which case an <constant>SD_BUS_ERROR_NO_MEMORY</constant> error will be set instead and + <constant>-ENOMEM</constant> returned. </para> <para><function>sd_bus_error_setf()</function> is similar to <function>sd_bus_error_set()</function>, but takes a <citerefentry @@ -204,33 +203,25 @@ <structfield>message</structfield> field.</para> <para><function>sd_bus_error_set_const()</function> is similar to - <function>sd_bus_error_set()</function>, but the string parameters - are not copied internally, and must hence remain constant and - valid for the lifetime of <parameter>e</parameter>. 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 - <function>sd_bus_error_set()</function> can, as described - above. Alternatively, the - <constant>SD_BUS_ERROR_MAKE_CONST()</constant> macro may be used - to generate a literal, constant bus error structure - on-the-fly.</para> - - <para><function>sd_bus_error_set_errno()</function> will set - <structfield>name</structfield> from an - <varname>errno</varname>-like value that is converted to a D-Bus + <function>sd_bus_error_set()</function>, but the string parameters are not copied internally, and must + hence remain constant and valid for the lifetime of <parameter>e</parameter>. 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 <function>sd_bus_error_set()</function> may, as described + above. Alternatively, the <constant>SD_BUS_ERROR_MAKE_CONST()</constant> macro may be used to generate a + literal, constant bus error structure on-the-fly.</para> + + <para><function>sd_bus_error_set_errno()</function> will immediately return <constant>0</constant> if the + specified error parameter <parameter>error</parameter> is <constant>0</constant>. Otherwise, it will set + <structfield>name</structfield> from an <varname>errno</varname>-like value that is converted to a D-Bus error. <citerefentry - project='die-net'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry> - will be used to set <structfield>message</structfield>. Well-known - D-Bus error names will be used for <structfield>name</structfield> - if applicable, otherwise a name in the - <literal>System.Error.</literal> 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 <function>return</function> statements. This - call might fail due to lack of memory, in which case an - <constant>SD_BUS_ERROR_NO_MEMORY</constant> error is set instead, - and -ENOMEM is returned.</para> + project='die-net'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry> will + be used to set <structfield>message</structfield>. Well-known D-Bus error names will be used for + <structfield>name</structfield> if applicable, otherwise a name in the <literal>System.Error.</literal> + namespace will be generated. The sign of the specified error number is ignored and the absolute value is + used implicitly. If the specified error <parameter>error</parameter> is non-zero, the call always returns + a negative value, for convenient usage in <function>return</function> statements. This call might fail + due to lack of memory, in which case an <constant>SD_BUS_ERROR_NO_MEMORY</constant> error is set instead, + and <constant>-ENOMEM</constant> is returned.</para> <para><function>sd_bus_error_set_errnof()</function> is similar to <function>sd_bus_error_set_errno()</function>, but in addition to @@ -246,28 +237,26 @@ project='man-pages'><refentrytitle>va_arg</refentrytitle><manvolnum>3</manvolnum></citerefentry> parameter list.</para> - <para><function>sd_bus_error_get_errno()</function> converts the - <structfield>name</structfield> field of an error structure to an - <varname>errno</varname>-like (positive) value using the same - rules as <function>sd_bus_error_set()</function>. If - <parameter>e</parameter> is <constant>NULL</constant>, 0 will be - returned.</para> - - <para><function>sd_bus_error_copy()</function> will initialize - <parameter>dst</parameter> using the values in - <parameter>e</parameter>. If the strings in - <parameter>e</parameter> were set using - <function>sd_bus_error_set_const()</function>, they will be shared. - Otherwise, they will be copied. Returns a converted - <varname>errno</varname>-like, negative error code.</para> - - <para><function>sd_bus_error_move()</function> is similar to <function>sd_bus_error_copy()</function>, but will - move any error information from <parameter>e</parameter> into <parameter>dst</parameter>, resetting the - former. This function cannot fail, as no new memory is allocated. Note that if <parameter>e</parameter> is not set - (or <constant>NULL</constant>) <parameter>dst</parameter> is initializated to - <constant>SD_BUS_ERROR_NULL</constant>. Moreover, if <parameter>dst</parameter> is <constant>NULL</constant> no - operation is executed on it and resources held by <parameter>e</parameter> are freed and reset. Returns a - converted <varname>errno</varname>-like, negative error code.</para> + <para><function>sd_bus_error_get_errno()</function> converts the <structfield>name</structfield> field of + an error structure to an <varname>errno</varname>-like (positive) value using the same rules as + <function>sd_bus_error_set()</function>. If <parameter>e</parameter> is <constant>NULL</constant>, + <constant>0</constant> will be returned.</para> + + <para><function>sd_bus_error_copy()</function> will initialize <parameter>dst</parameter> using the + values in <parameter>e</parameter>, if <parameter>e</parameter> has been set with an error value before. + Otherwise, it will return immediately. If the strings in <parameter>e</parameter> were set using + <function>sd_bus_error_set_const()</function>, they will be shared. Otherwise, they will be + copied. Returns a converted <varname>errno</varname>-like, negative error code or <constant>0</constant>. + Before this call, <parameter>dst</parameter> must be unset, i.e. either freshly initialized with + <constant>NULL</constant> or reset using <function>sd_bus_error_free()</function>.</para> + + <para><function>sd_bus_error_move()</function> is similar to <function>sd_bus_error_copy()</function>, + but will move any error information from <parameter>e</parameter> into <parameter>dst</parameter>, + resetting the former. This function cannot fail, as no new memory is allocated. Note that if + <parameter>e</parameter> is not set, <parameter>dst</parameter> is initializated to + <constant>SD_BUS_ERROR_NULL</constant>. Moreover, if <parameter>dst</parameter> is + <constant>NULL</constant> no operation is executed on it and resources held by <parameter>e</parameter> + are freed and reset. Returns a converted <varname>errno</varname>-like, non-positive error value.</para> <para><function>sd_bus_error_is_set()</function> will return a non-zero value if <parameter>e</parameter> is @@ -300,25 +289,23 @@ <refsect1> <title>Return Value</title> - <para>The functions <function>sd_bus_error_set()</function>, - <function>sd_bus_error_setf()</function>, and - <function>sd_bus_error_set_const()</function>, when successful, - return the negative errno value corresponding to the - <parameter>name</parameter> parameter. The functions - <function>sd_bus_error_set_errno()</function>, - <function>sd_bus_error_set_errnof()</function> and - <function>sd_bus_error_set_errnofv()</function>, when successful, - return the negative value of the <parameter>error</parameter> - parameter. If an error occurs, one of the negative error values - listed below will be returned.</para> + <para>The functions <function>sd_bus_error_set()</function>, <function>sd_bus_error_setf()</function>, + and <function>sd_bus_error_set_const()</function> always return <constant>0</constant> when the specified + error value is <constant>NULL</constant>, and a negative errno-like value corresponding to the + <parameter>name</parameter> parameter otherwise. The functions + <function>sd_bus_error_set_errno()</function>, <function>sd_bus_error_set_errnof()</function> and + <function>sd_bus_error_set_errnofv()</function>, return <constant>0</constant> when the specified error + value is <constant>0</constant>, and a a negative errno-like value corresponding to the + <parameter>error</parameter> parameter otherwise. If an error occurs internally, one of the negative + error values listed below will be returned.</para> <para><function>sd_bus_error_get_errno()</function> returns <constant>false</constant> when <parameter>e</parameter> is <constant>NULL</constant>, and a positive errno value mapped from <parameter>e->name</parameter> otherwise.</para> - <para><function>sd_bus_error_copy()</function> and <function>sd_bus_error_move()</function> return 0 or a positive - integer on success, and a negative error value converted from the error name otherwise.</para> + <para><function>sd_bus_error_copy()</function> and <function>sd_bus_error_move()</function> return a + negative error value converted from the source error, and zero if the error has not been set.</para> <para><function>sd_bus_error_is_set()</function> returns a non-zero value when <parameter>e</parameter> 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); |