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113 lines
4.9 KiB
XML
113 lines
4.9 KiB
XML
<?xml version='1.0'?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1+ -->
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<refentry id="sd_event_source_set_destroy_callback"
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xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_event_source_set_destroy_callback</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_event_source_set_destroy_callback</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_event_source_set_destroy_callback</refname>
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<refname>sd_event_source_get_destroy_callback</refname>
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<refname>sd_event_destroy_t</refname>
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<refpurpose>Define the callback function for resource cleanup.</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>typedef int (*<function>sd_event_destroy_t</function>)</funcdef>
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<paramdef>void *<parameter>userdata</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_event_source_set_destroy_callback</function></funcdef>
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<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
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<paramdef>sd_event_destroy_t <parameter>callback</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_event_source_get_destroy_callback</function></funcdef>
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<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
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<paramdef>sd_event_destroy_t *<parameter>callback</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_event_source_set_destroy_callback()</function> sets <parameter>callback</parameter> as the
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callback function to be called right before the event source object <parameter>source</parameter> is
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deallocated. The <parameter>userdata</parameter> pointer from the event source object will be passed as the
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<parameter>userdata</parameter> parameter. This pointer can be set by an argument to the constructor functions, see
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<citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>, or directly,
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see
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<citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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This callback function is called even if <parameter>userdata</parameter> is <constant>NULL</constant>. Note that
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this callback is invoked at a time where the event source object itself is already invalidated, and executing
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operations or taking new references to the event source object is not permissible.</para>
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<para><function>sd_event_source_get_destroy_callback()</function> returns the current callback
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for <parameter>source</parameter> in the <parameter>callback</parameter> parameter.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>On success, <function>sd_event_source_set_destroy_callback()</function> returns 0 or a positive integer. On
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failure, it returns a negative errno-style error code.</para>
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<para><function>sd_event_source_get_destroy_callback()</function> returns positive if the destroy callback function
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is set, 0 if not. On failure, returns a negative errno-style error code.</para>
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</refsect1>
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<refsect1>
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<title>Errors</title>
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<para>Returned errors may indicate the following problems:</para>
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<variablelist>
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<varlistentry>
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<term><constant>-EINVAL</constant></term>
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<listitem><para>The <parameter>source</parameter> parameter is <constant>NULL</constant>.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<xi:include href="libsystemd-pkgconfig.xml" />
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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