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514094f9 | 1 | <?xml version='1.0'?> |
71365a77 | 2 | <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" |
12b42c76 | 3 | "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> |
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4 | |
5 | <!-- | |
572eb058 | 6 | SPDX-License-Identifier: LGPL-2.1+ |
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7 | --> |
8 | ||
7d6b2723 | 9 | <refentry id="sd_bus_error" xmlns:xi="http://www.w3.org/2001/XInclude"> |
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10 | |
11 | <refentryinfo> | |
12 | <title>sd_bus_error</title> | |
13 | <productname>systemd</productname> | |
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14 | </refentryinfo> |
15 | ||
16 | <refmeta> | |
17 | <refentrytitle>sd_bus_error</refentrytitle> | |
18 | <manvolnum>3</manvolnum> | |
19 | </refmeta> | |
20 | ||
21 | <refnamediv> | |
22 | <refname>sd_bus_error</refname> | |
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23 | <refname>SD_BUS_ERROR_MAKE_CONST</refname> |
24 | <refname>SD_BUS_ERROR_NULL</refname> | |
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25 | <refname>sd_bus_error_free</refname> |
26 | <refname>sd_bus_error_set</refname> | |
9d3e5d11 | 27 | <refname>sd_bus_error_setf</refname> |
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28 | <refname>sd_bus_error_set_const</refname> |
29 | <refname>sd_bus_error_set_errno</refname> | |
30 | <refname>sd_bus_error_set_errnof</refname> | |
9d3e5d11 | 31 | <refname>sd_bus_error_set_errnofv</refname> |
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32 | <refname>sd_bus_error_get_errno</refname> |
33 | <refname>sd_bus_error_copy</refname> | |
190128e4 | 34 | <refname>sd_bus_error_move</refname> |
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35 | <refname>sd_bus_error_is_set</refname> |
36 | <refname>sd_bus_error_has_name</refname> | |
37 | ||
6bb648a1 | 38 | <refpurpose>sd-bus error handling</refpurpose> |
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39 | </refnamediv> |
40 | ||
41 | <refsynopsisdiv> | |
42 | <funcsynopsis> | |
43 | <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> | |
44 | ||
45 | <funcsynopsisinfo>typedef struct { | |
46 | const char *name; | |
47 | const char *message; | |
1eecafb8 | 48 | … |
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49 | } sd_bus_error;</funcsynopsisinfo> |
50 | ||
51 | <para> | |
52 | <constant>SD_BUS_ERROR_MAKE_CONST(<replaceable>name</replaceable>, <replaceable>message</replaceable>)</constant> | |
53 | </para> | |
54 | <para> | |
55 | <constant>SD_BUS_ERROR_NULL</constant> | |
56 | </para> | |
57 | ||
58 | <funcprototype> | |
9d3e5d11 | 59 | <funcdef>void <function>sd_bus_error_free</function></funcdef> |
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60 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> |
61 | </funcprototype> | |
62 | ||
63 | <funcprototype> | |
64 | <funcdef>int <function>sd_bus_error_set</function></funcdef> | |
65 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
66 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
67 | <paramdef>const char *<parameter>message</parameter></paramdef> | |
68 | </funcprototype> | |
69 | ||
70 | <funcprototype> | |
71 | <funcdef>int <function>sd_bus_error_setf</function></funcdef> | |
72 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
73 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
74 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
1eecafb8 | 75 | <paramdef>…</paramdef> |
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76 | </funcprototype> |
77 | ||
78 | <funcprototype> | |
79 | <funcdef>int <function>sd_bus_error_set_const</function></funcdef> | |
80 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
81 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
82 | <paramdef>const char *<parameter>message</parameter></paramdef> | |
83 | </funcprototype> | |
84 | ||
85 | <funcprototype> | |
86 | <funcdef>int <function>sd_bus_error_set_errno</function></funcdef> | |
87 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
88 | <paramdef>int <parameter>error</parameter></paramdef> | |
89 | </funcprototype> | |
90 | ||
91 | <funcprototype> | |
92 | <funcdef>int <function>sd_bus_error_set_errnof</function></funcdef> | |
93 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
94 | <paramdef>int <parameter>error</parameter></paramdef> | |
95 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
1eecafb8 | 96 | <paramdef>…</paramdef> |
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97 | </funcprototype> |
98 | ||
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99 | <funcprototype> |
100 | <funcdef>int <function>sd_bus_error_set_errnofv</function></funcdef> | |
101 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
102 | <paramdef>int <parameter>error</parameter></paramdef> | |
103 | <paramdef>const char *<parameter>format</parameter></paramdef> | |
c765233c | 104 | <paramdef>va_list <parameter>ap</parameter></paramdef> |
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105 | </funcprototype> |
106 | ||
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107 | <funcprototype> |
108 | <funcdef>int <function>sd_bus_error_get_errno</function></funcdef> | |
109 | <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> | |
110 | </funcprototype> | |
111 | ||
112 | <funcprototype> | |
113 | <funcdef>int <function>sd_bus_error_copy</function></funcdef> | |
114 | <paramdef>sd_bus_error *<parameter>dst</parameter></paramdef> | |
115 | <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> | |
116 | </funcprototype> | |
117 | ||
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118 | <funcprototype> |
119 | <funcdef>int <function>sd_bus_error_move</function></funcdef> | |
120 | <paramdef>sd_bus_error *<parameter>dst</parameter></paramdef> | |
121 | <paramdef>sd_bus_error *<parameter>e</parameter></paramdef> | |
122 | </funcprototype> | |
123 | ||
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124 | <funcprototype> |
125 | <funcdef>int <function>sd_bus_error_is_set</function></funcdef> | |
126 | <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> | |
127 | </funcprototype> | |
128 | ||
129 | <funcprototype> | |
130 | <funcdef>int <function>sd_bus_error_has_name</function></funcdef> | |
131 | <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef> | |
132 | <paramdef>const char *<parameter>name</parameter></paramdef> | |
133 | </funcprototype> | |
134 | </funcsynopsis> | |
135 | ||
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136 | </refsynopsisdiv> |
137 | ||
138 | <refsect1> | |
139 | <title>Description</title> | |
140 | ||
66f756d4 | 141 | <para>The <structname>sd_bus_error</structname> structure carries |
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142 | information about a D-Bus error condition. The functions described |
143 | below may be used to set and query fields in this structure. The | |
144 | <structfield>name</structfield> field contains a short identifier | |
145 | of an error. It should follow the rules for error names described | |
146 | in the D-Bus specification, subsection <ulink | |
71365a77 | 147 | url="http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names">Valid |
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148 | Names</ulink>. A number of common, standardized error names are |
149 | described in | |
150 | <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
151 | but additional domain-specific errors may be defined by | |
152 | applications. The <structfield>message</structfield> field usually | |
b938cb90 | 153 | contains a human-readable string describing the details, but might |
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154 | be NULL. An unset <structname>sd_bus_error</structname> structure |
155 | should have both fields initialized to NULL. Set an error | |
156 | structure to <constant>SD_BUS_ERROR_NULL</constant> in order to | |
157 | reset both fields to NULL. When no longer necessary, resources | |
74fb9617 | 158 | held by the <structname>sd_bus_error</structname> structure should |
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159 | be destroyed with <function>sd_bus_error_free()</function>.</para> |
160 | ||
161 | <para><function>sd_bus_error_set()</function> sets an error | |
162 | structure to the specified name and message strings. The strings | |
163 | will be copied into internal, newly allocated memory. It is | |
164 | essential to free the error structure again when it is not | |
165 | required anymore (see above). The function will return an | |
166 | <varname>errno</varname>-like negative value (see <citerefentry | |
167 | project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>) | |
168 | determined from the specified error name. Various well-known | |
169 | D-Bus errors are converted to well-known <varname>errno</varname> | |
170 | counterparts, and the other ones to <constant>-EIO</constant>. See | |
171 | <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
172 | for a list of well-known error names. Additional error mappings | |
173 | may be defined with | |
174 | <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If | |
b938cb90 | 175 | <parameter>e</parameter> is NULL, no error structure is initialized, |
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176 | but the error is still converted into an |
177 | <varname>errno</varname>-style error. If | |
66f756d4 | 178 | <parameter>name</parameter> is <constant>NULL</constant>, it is |
06b643e7 | 179 | assumed that no error occurred, and 0 is returned. This means that |
71365a77 | 180 | this function may be conveniently used in a |
9d3e5d11 | 181 | <function>return</function> statement. If |
b938cb90 | 182 | <parameter>message</parameter> is NULL, no message is set. This |
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183 | call can fail if no memory may be allocated for the name and |
184 | message strings, in which case an | |
185 | <constant>SD_BUS_ERROR_NO_MEMORY</constant> error might be set | |
a8eaaee7 | 186 | instead and -ENOMEM be returned. Do not use this call on error |
9d3e5d11 | 187 | structures that are already initialized. If you intend to reuse an |
b938cb90 | 188 | error structure, free the old data stored in it with |
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189 | <function>sd_bus_error_free()</function> first.</para> |
190 | ||
191 | <para><function>sd_bus_error_setf()</function> is similar to | |
192 | <function>sd_bus_error_set()</function>, but takes a <citerefentry | |
193 | project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
194 | format string and corresponding arguments to generate the | |
195 | <structfield>message</structfield> field.</para> | |
196 | ||
197 | <para><function>sd_bus_error_set_const()</function> is similar to | |
198 | <function>sd_bus_error_set()</function>, but the string parameters | |
199 | are not copied internally, and must hence remain constant and | |
200 | valid for the lifetime of <parameter>e</parameter>. Use this call | |
201 | to avoid memory allocations when setting error structures. Since | |
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202 | this call does not allocate memory, it will not fail with an |
203 | out-of-memory condition as | |
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204 | <function>sd_bus_error_set()</function> can, as described |
205 | above. Alternatively, the | |
206 | <constant>SD_BUS_ERROR_MAKE_CONST()</constant> macro may be used | |
207 | to generate a literal, constant bus error structure | |
208 | on-the-fly.</para> | |
209 | ||
210 | <para><function>sd_bus_error_set_errno()</function> will set | |
211 | <structfield>name</structfield> from an | |
212 | <varname>errno</varname>-like value that is converted to a D-Bus | |
213 | error. <citerefentry | |
214 | project='die-net'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
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215 | will be used to set <structfield>message</structfield>. Well-known |
216 | D-Bus error names will be used for <structfield>name</structfield> | |
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217 | if applicable, otherwise a name in the |
218 | <literal>System.Error.</literal> namespace will be generated. The | |
219 | sign of the specified error number is ignored. The absolute value | |
220 | is used implicitly. The call always returns a negative value, for | |
221 | convenient usage in <function>return</function> statements. This | |
222 | call might fail due to lack of memory, in which case an | |
223 | <constant>SD_BUS_ERROR_NO_MEMORY</constant> error is set instead, | |
a8eaaee7 | 224 | and -ENOMEM is returned.</para> |
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225 | |
226 | <para><function>sd_bus_error_set_errnof()</function> is similar to | |
227 | <function>sd_bus_error_set_errno()</function>, but in addition to | |
228 | <parameter>error</parameter>, takes a <citerefentry | |
229 | project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
230 | format string and corresponding arguments. The | |
231 | <structfield>message</structfield> field will be generated from | |
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232 | <parameter>format</parameter> and the arguments.</para> |
233 | ||
9d3e5d11 | 234 | <para><function>sd_bus_error_set_errnofv()</function> is similar to |
b938cb90 | 235 | <function>sd_bus_error_set_errnof()</function>, but takes the |
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236 | format string parameters as <citerefentry |
237 | project='man-pages'><refentrytitle>va_arg</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
238 | parameter list.</para> | |
239 | ||
240 | <para><function>sd_bus_error_get_errno()</function> converts the | |
241 | <structfield>name</structfield> field of an error structure to an | |
242 | <varname>errno</varname>-like (positive) value using the same | |
243 | rules as <function>sd_bus_error_set()</function>. If | |
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244 | <parameter>e</parameter> is <constant>NULL</constant>, 0 will be |
245 | returned.</para> | |
71365a77 | 246 | |
9d3e5d11 | 247 | <para><function>sd_bus_error_copy()</function> will initialize |
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248 | <parameter>dst</parameter> using the values in |
249 | <parameter>e</parameter>. If the strings in | |
250 | <parameter>e</parameter> were set using | |
78c1edd1 | 251 | <function>sd_bus_error_set_const()</function>, they will be shared. |
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252 | Otherwise, they will be copied. Returns a converted |
253 | <varname>errno</varname>-like, negative error code.</para> | |
71365a77 | 254 | |
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255 | <para><function>sd_bus_error_move()</function> is similar to <function>sd_bus_error_copy()</function>, but will |
256 | move any error information from <parameter>e</parameter> into <parameter>dst</parameter>, resetting the | |
257 | former. This function cannot fail, as no new memory is allocated. Note that if <parameter>e</parameter> is not set | |
258 | (or <constant>NULL</constant>) <parameter>dst</parameter> is initializated to | |
259 | <constant>SD_BUS_ERROR_NULL</constant>. Moreover, if <parameter>dst</parameter> is <constant>NULL</constant> no | |
260 | operation is executed on it and and resources held by <parameter>e</parameter> are freed and reset. Returns a | |
261 | converted <varname>errno</varname>-like, negative error code.</para> | |
262 | ||
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263 | <para><function>sd_bus_error_is_set()</function> will return a |
264 | non-zero value if <parameter>e</parameter> is | |
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265 | non-<constant>NULL</constant> and an error has been set, |
266 | <constant>false</constant> otherwise.</para> | |
267 | ||
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268 | <para><function>sd_bus_error_has_name()</function> will return a |
269 | non-zero value if <parameter>e</parameter> is | |
270 | non-<constant>NULL</constant> and an error with the same | |
271 | <parameter>name</parameter> has been set, | |
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272 | <constant>false</constant> otherwise.</para> |
273 | ||
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274 | <para><function>sd_bus_error_free()</function> will destroy |
275 | resources held by <parameter>e</parameter>. The parameter itself | |
276 | will not be deallocated, and must be <citerefentry | |
277 | project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>d | |
278 | by the caller if necessary. The function may also be called safely | |
279 | on unset errors (error structures with both fields set to NULL), | |
280 | in which case it performs no operation. This call will reset the | |
281 | error structure after freeing the data, so that all fields are set | |
282 | to NULL. The structure may be reused afterwards.</para> | |
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283 | </refsect1> |
284 | ||
285 | <refsect1> | |
286 | <title>Return Value</title> | |
287 | ||
9d3e5d11 | 288 | <para>The functions <function>sd_bus_error_set()</function>, |
a8eaaee7 | 289 | <function>sd_bus_error_setf()</function>, and |
9d3e5d11 | 290 | <function>sd_bus_error_set_const()</function>, when successful, |
71365a77 | 291 | return the negative errno value corresponding to the |
a8eaaee7 | 292 | <parameter>name</parameter> parameter. The functions |
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293 | <function>sd_bus_error_set_errno()</function>, |
294 | <function>sd_bus_error_set_errnof()</function> and | |
295 | <function>sd_bus_error_set_errnofv()</function>, when successful, | |
296 | return the negative value of the <parameter>error</parameter> | |
297 | parameter. If an error occurs, one of the negative error values | |
298 | listed below will be returned.</para> | |
299 | ||
300 | <para><function>sd_bus_error_get_errno()</function> returns | |
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301 | <constant>false</constant> when <parameter>e</parameter> is |
302 | <constant>NULL</constant>, and a positive errno value mapped from | |
3c8fa0fd | 303 | <parameter>e->name</parameter> otherwise.</para> |
71365a77 | 304 | |
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305 | <para><function>sd_bus_error_copy()</function> and <function>sd_bus_error_move()</function> return 0 or a positive |
306 | integer on success, and a negative error value converted from the error name otherwise.</para> | |
71365a77 | 307 | |
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308 | <para><function>sd_bus_error_is_set()</function> returns a |
309 | non-zero value when <parameter>e</parameter> and the | |
310 | <structfield>name</structfield> field are | |
311 | non-<constant>NULL</constant>, zero otherwise.</para> | |
71365a77 | 312 | |
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313 | <para><function>sd_bus_error_has_name()</function> returns a |
314 | non-zero value when <parameter>e</parameter> is | |
315 | non-<constant>NULL</constant> and the | |
316 | <structfield>name</structfield> field is equal to | |
317 | <parameter>name</parameter>, zero otherwise.</para> | |
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318 | </refsect1> |
319 | ||
320 | <refsect1> | |
321 | <title>Reference ownership</title> | |
322 | <para><structname>sd_bus_error</structname> is not reference | |
323 | counted. Users should destroy resources held by it by calling | |
b938cb90 | 324 | <function>sd_bus_error_free()</function>. Usually, error structures |
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325 | are allocated on the stack or passed in as function parameters, |
326 | but they may also be allocated dynamically, in which case it is | |
327 | the duty of the caller to <citerefentry | |
328 | project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry> | |
329 | the memory held by the structure itself after freeing its contents | |
330 | with <function>sd_bus_error_free()</function>.</para> | |
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331 | </refsect1> |
332 | ||
333 | <refsect1> | |
334 | <title>Errors</title> | |
335 | ||
336 | <para>Returned errors may indicate the following problems:</para> | |
337 | ||
338 | <variablelist> | |
339 | ||
340 | <varlistentry> | |
8474b70c | 341 | <term><constant>-EINVAL</constant></term> |
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342 | |
343 | <listitem><para>Error was already set in | |
344 | <structname>sd_bus_error</structname> structure when one the | |
345 | error-setting functions was called.</para></listitem> | |
346 | </varlistentry> | |
347 | ||
348 | <varlistentry> | |
8474b70c | 349 | <term><constant>-ENOMEM</constant></term> |
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350 | |
351 | <listitem><para>Memory allocation failed.</para></listitem> | |
352 | </varlistentry> | |
353 | </variablelist> | |
354 | </refsect1> | |
355 | ||
7d6b2723 | 356 | <xi:include href="libsystemd-pkgconfig.xml" /> |
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357 | |
358 | <refsect1> | |
359 | <title>See Also</title> | |
360 | ||
361 | <para> | |
362 | <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, | |
363 | <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
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364 | <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
365 | <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>, | |
5aded369 | 366 | <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>, |
9d3e5d11 | 367 | <citerefentry project='die-net'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry> |
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368 | </para> |
369 | </refsect1> | |
370 | ||
371 | </refentry> |