Adding upstream version 252.22.upstream/252.22upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 408 insertions, 0 deletions

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+<?xml version='1.0'?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
+
+<refentry id="sd_bus_error" xmlns:xi="http://www.w3.org/2001/XInclude">
+
+  <refentryinfo>
+    <title>sd_bus_error</title>
+    <productname>systemd</productname>
+  </refentryinfo>
+
+  <refmeta>
+    <refentrytitle>sd_bus_error</refentrytitle>
+    <manvolnum>3</manvolnum>
+  </refmeta>
+
+  <refnamediv>
+    <refname>sd_bus_error</refname>
+    <refname>SD_BUS_ERROR_MAKE_CONST</refname>
+    <refname>SD_BUS_ERROR_NULL</refname>
+    <refname>sd_bus_error_free</refname>
+    <refname>sd_bus_error_set</refname>
+    <refname>sd_bus_error_setf</refname>
+    <refname>sd_bus_error_setfv</refname>
+    <refname>sd_bus_error_set_const</refname>
+    <refname>sd_bus_error_set_errno</refname>
+    <refname>sd_bus_error_set_errnof</refname>
+    <refname>sd_bus_error_set_errnofv</refname>
+    <refname>sd_bus_error_get_errno</refname>
+    <refname>sd_bus_error_copy</refname>
+    <refname>sd_bus_error_move</refname>
+    <refname>sd_bus_error_is_set</refname>
+    <refname>sd_bus_error_has_name</refname>
+    <refname>sd_bus_error_has_names_sentinel</refname>
+    <refname>sd_bus_error_has_names</refname>
+
+    <refpurpose>sd-bus error handling</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <funcsynopsis>
+      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>
+
+      <funcsynopsisinfo>typedef struct {
+        const char *name;
+        const char *message;
+        …
+} sd_bus_error;</funcsynopsisinfo>
+
+      <para>
+        <constant>SD_BUS_ERROR_MAKE_CONST(<replaceable>name</replaceable>, <replaceable>message</replaceable>)</constant>
+      </para>
+      <para>
+        <constant>SD_BUS_ERROR_NULL</constant>
+      </para>
+
+      <funcprototype>
+        <funcdef>void <function>sd_bus_error_free</function></funcdef>
+        <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_error_set</function></funcdef>
+        <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
+        <paramdef>const char *<parameter>name</parameter></paramdef>
+        <paramdef>const char *<parameter>message</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_error_setf</function></funcdef>
+        <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
+        <paramdef>const char *<parameter>name</parameter></paramdef>
+        <paramdef>const char *<parameter>format</parameter></paramdef>
+        <paramdef>…</paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_error_setfv</function></funcdef>
+        <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
+        <paramdef>const char *<parameter>name</parameter></paramdef>
+        <paramdef>const char *<parameter>format</parameter></paramdef>
+        <paramdef>va_list <parameter>ap</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_error_set_const</function></funcdef>
+        <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
+        <paramdef>const char *<parameter>name</parameter></paramdef>
+        <paramdef>const char *<parameter>message</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_error_set_errno</function></funcdef>
+        <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
+        <paramdef>int <parameter>error</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_error_set_errnof</function></funcdef>
+        <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
+        <paramdef>int <parameter>error</parameter></paramdef>
+        <paramdef>const char *<parameter>format</parameter></paramdef>
+        <paramdef>…</paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_error_set_errnofv</function></funcdef>
+        <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
+        <paramdef>int <parameter>error</parameter></paramdef>
+        <paramdef>const char *<parameter>format</parameter></paramdef>
+        <paramdef>va_list <parameter>ap</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_error_get_errno</function></funcdef>
+        <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_error_copy</function></funcdef>
+        <paramdef>sd_bus_error *<parameter>dst</parameter></paramdef>
+        <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_error_move</function></funcdef>
+        <paramdef>sd_bus_error *<parameter>dst</parameter></paramdef>
+        <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_error_is_set</function></funcdef>
+        <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_error_has_name</function></funcdef>
+        <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
+        <paramdef>const char *<parameter>name</parameter></paramdef>
+      </funcprototype>
+
+      <funcprototype>
+        <funcdef>int <function>sd_bus_error_has_names_sentinel</function></funcdef>
+        <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
+        <paramdef>...</paramdef>
+      </funcprototype>
+
+      <para>
+        &#35;define sd_bus_error_has_names(e, ...) sd_bus_error_has_names_sentinel(e, ..., NULL)
+      </para>
+    </funcsynopsis>
+
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Description</title>
+
+    <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="https://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 <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> and <function>sd_bus_error_setfv()</function> are similar
+    to <function>sd_bus_error_set()</function>, but take a <citerefentry
+    project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> format
+    string and corresponding arguments to generate the <structfield>message</structfield> field.
+    <function>sd_bus_error_setf()</function> uses variadic arguments, and
+    <function>sd_bus_error_setfv()</function> accepts the arguments as a
+    <citerefentry
+    project='man-pages'><refentrytitle>va_arg</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    parameter list.</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> 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 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> and <function>sd_bus_error_set_errnof()</function>
+    are similar to <function>sd_bus_error_set_errno()</function>, but in addition to
+    <parameter>error</parameter>, take a <citerefentry
+    project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> format
+    string and corresponding arguments. The <structfield>message</structfield> field will be generated from
+    <parameter>format</parameter> and the arguments.
+    <function>sd_bus_error_set_errnof()</function> uses variadic arguments, and
+    <function>sd_bus_error_set_errnofv()</function> accepts the arguments as a
+    <citerefentry
+    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>,
+    <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. 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_copy()</function> generally returns <constant>0</constant> or a negative
+    <varname>errno</varname>-like value based on the input parameter <parameter>e</parameter>:
+    <constant>0</constant> if it was unset and a negative integer if it was set to some error, similarly to
+    <function>sd_bus_error_set()</function>. It may however also return an error generated internally, for
+    example <constant>-ENOMEM</constant> if a memory allocation fails.</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 initialized 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
+    non-<constant>NULL</constant> and an error has been set,
+    <constant>false</constant> otherwise.</para>
+
+    <para><function>sd_bus_error_has_name()</function> will return a
+    non-zero value if <parameter>e</parameter> is
+    non-<constant>NULL</constant> and an error with the same
+    <parameter>name</parameter> has been set,
+    <constant>false</constant> otherwise.</para>
+
+    <para><function>sd_bus_error_has_names_sentinel()</function> is similar to
+    <function>sd_bus_error_has_name()</function>, but takes multiple names to check against. The list must be
+    terminated with <constant>NULL</constant>. <function>sd_bus_error_has_names()</function>
+    is a macro wrapper around <function>sd_bus_error_has_names_sentinel()</function> that adds the
+    <constant>NULL</constant> sentinel automatically.</para>
+
+    <para><function>sd_bus_error_free()</function> will destroy
+    resources held by <parameter>e</parameter>. The parameter itself
+    will not be deallocated, and must be <citerefentry
+    project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>d
+    by the caller if necessary. The function may also be called safely
+    on unset errors (error structures with both fields set to <constant>NULL</constant>),
+    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 <constant>NULL</constant>. The structure may be reused afterwards.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>Reference ownership</title>
+
+    <para><structname>sd_bus_error</structname> is not reference-counted. Users should destroy resources held
+    by it by calling <function>sd_bus_error_free()</function>. 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 <citerefentry
+    project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry> the memory
+    held by the structure itself after freeing its contents with
+    <function>sd_bus_error_free()</function>.</para>
+  </refsect1>
+
+  <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> 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 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. This allows those functions to be conveniently used in a
+    <constant>return</constant> statement, see the example below.</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-&gt;name</parameter> 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.  This
+    allows those functions to be conveniently used in a <constant>return</constant> statement, see the
+    example below.</para>
+
+    <para><function>sd_bus_error_is_set()</function> returns a
+    non-zero value when <parameter>e</parameter> and the
+    <structfield>name</structfield> field are
+    non-<constant>NULL</constant>, zero otherwise.</para>
+
+    <para><function>sd_bus_error_has_name()</function>, <function>sd_bus_error_has_names()</function>, and
+    <function>sd_bus_error_has_names_sentinel()</function> return a non-zero value when <parameter>e</parameter> is
+    non-<constant>NULL</constant> and the <structfield>name</structfield> field is equal to one of the given
+    names, zero otherwise.</para>
+
+    <refsect2>
+      <title>Errors</title>
+
+      <para>Return value may indicate the following problems in the invocation of the function itself:</para>
+
+      <variablelist>
+        <varlistentry>
+          <term><constant>-EINVAL</constant></term>
+
+          <listitem><para>Error was already set in the <structname>sd_bus_error</structname> structure when
+          one the error-setting functions was called.</para></listitem>
+        </varlistentry>
+
+        <varlistentry>
+          <term><constant>-ENOMEM</constant></term>
+
+          <listitem><para>Memory allocation failed.</para></listitem>
+        </varlistentry>
+      </variablelist>
+
+      <para>On success, <function>sd_bus_error_set()</function>, <function>sd_bus_error_setf()</function>,
+      <function>sd_bus_error_set_const()</function>, <function>sd_bus_error_set_errno()</function>,
+      <function>sd_bus_error_set_errnof()</function>, <function>sd_bus_error_set_errnofv()</function>,
+      <function>sd_bus_error_copy()</function>, and <function>sd_bus_error_move()</function> will return a
+      negative converted <varname>errno</varname>-style value, or <constant>0</constant> if the error
+      parameter is <constant>NULL</constant> or unset. D-Bus errors are converted to the integral
+      <varname>errno</varname>-style value, and the mapping mechanism is extensible, see the discussion
+      above. This effectively means that almost any negative <varname>errno</varname>-style value can be
+      returned.</para>
+    </refsect2>
+  </refsect1>
+
+  <refsect1>
+    <title>Examples</title>
+
+    <example>
+      <title>Using the negative return value to propagate an error</title>
+
+      <programlisting><xi:include href="sd_bus_error-example.c" parse="text" /></programlisting>
+    </example>
+  </refsect1>
+
+  <xi:include href="libsystemd-pkgconfig.xml" />
+
+  <refsect1>
+    <title>See Also</title>
+
+    <para>
+      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+      <citerefentry project='man-pages'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    </para>
+  </refsect1>
+
+</refentry>