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36 <i><b>Contents</b></i></td>
39 <td width="100%" bgcolor="#E8F5FF">
40 <a href="#Introduction">Introduction</a><br>
41 <a href="#C++11">C++11</a><br>
42 <a href="#Macros">Macros</a><br>
43 <a href="#Deprecated-names">Deprecated names</a><br>
44 <a href="#Breaking-changes">Breaking changes</a><br>
45 <a href="#Header-error_code">Header <boost/system/error_code.hpp></a><br>
46 <a href="#Class-error_category">Class <code>error_category</code></a><br>
47 <a href="#Class-error_category-synopsis">Class <code>error_category</code> synopsis</a><br>
48 <a href="#Class-error_category-virtual-members">Class <code>error_category</code> virtual members</a><br>
49 <a href="#Class-error_category-non-virtual-members">Class <code>error_category</code> non-virtual members</a><br>
50 <a href="#Class-error_category-non-member-functions">Class <code>error_category</code>
51 non-member functions</a><br>
52 <a href="#Class-error_category-predefined-objects">Class <code>error_category</code> predefined objects</a><br>
53 <a href="#Class-error_code">Class <code>error_code</code></a><br>
54 <a href="#Class-error_code-synopsis">Class <code>error_code</code> synopsis</a><br>
55 <a href="#Class-error_code-constructors">Class <code>error_code</code> constructors</a><br>
56 <a href="#Class-error_code-modifiers">Class <code>error_code</code> modifiers</a><br>
57 <a href="#Class-error_code-observers">Class <code>error_code</code> observers</a><br>
58 <a href="#Class-error_condition">Class <code>error_condition</code></a><br>
59 <a href="#Class-error_condition-synopsis">Class <code>error_condition</code> synopsis</a><br>
60 <a href="#Class-error_condition-constructors">Class <code>error_condition</code> constructors</a><br>
61 <a href="#Class-error_condition-modifiers">Class <code>error_condition</code> modifiers</a><br>
62 <a href="#Class-error_condition-observers">Class <code>error_condition</code> observers</a><br>
63 <a href="#throws-object"><code>throws</code> object</a><br>
64 <a href="#Semantics-of-throws">Semantics of <code>throws</code> object</a><br>
65 <a href="#Non-member-functions">Non-member functions</a><br>
66 <a href="#Header-system_error">Header <boost/system/system_error.hpp></a><br>
67 <a href="#Class-system_error">Class <code>system_error</code></a><br>
72 <h2><a name="Introduction">Introduction</a></h2>
74 <p>This reference documentation describes components that programs may use to report error conditions originating from the operating
75 system or other low-level application program interfaces.</p>
76 <p>Boost.System library components never change the value of <code>
78 <h2><a name="C++11">C++11</a></h2>
79 <p>The library is documented to use several C++11 features, including <code>
80 noexcept</code> and explicit conversion operators. The actual implementation
81 uses C++11 features only when they are available, and otherwise falls back on
83 <h2><a name="Macros">Macros</a></h2>
84 <p>Users may defined the following macros if desired. Sensible defaults are
85 provided, so users may ignore these macros if they prefer.</p>
86 <table border="1" cellpadding="5" cellspacing="0" style="border-collapse: collapse" bordercolor="#111111" height="368">
88 <td height="16"><b><i>Macro Name</i></b></td>
89 <td height="16"><b><i>Default</i></b></td>
90 <td height="16"><b><i>Effect if defined</i></b></td>
93 <td valign="top" height="64"><code>BOOST_ERROR_CODE_HEADER_ONLY</code></td>
94 <td valign="top" height="64">Not defined.</td>
95 <td valign="top" height="64">The implementation is header-only, and the
96 Boost.System library is not built. Overrides other link and library macros.</td>
99 <td valign="top" height="64"><code>BOOST_SYSTEM_DYN_LINK</code></td>
100 <td valign="top" height="64">Defined if <code>BOOST_ALL_DYN_LINK</code> is defined,
101 otherwise not defined.</td>
102 <td valign="top" height="64">Boost.System library is dynamically linked. If not defined,
103 static linking is assumed.</td>
106 <td valign="top" height="47"><code>BOOST_SYSTEM_NO_LIB</code></td>
107 <td valign="top" height="47">Defined if <code>BOOST_ALL_NO_LIB</code> is defined,
108 otherwise not defined.</td>
109 <td valign="top" height="47">Boost.System library does not use the Boost auto-link
113 <td valign="top" height="32"><code>BOOST_SYSTEM_NO_DEPRECATED</code></td>
114 <td valign="top" height="32">Not defined.</td>
115 <td valign="top" height="32">Deprecated features are excluded.</td>
118 <h2><a name="Deprecated-names">Deprecated names</a></h2>
119 <p>In the process of adding Boost.System to C++0x standard library, the C++
120 committee changed some
121 names. To ease transition, Boost.System deprecates the old
122 names, but continues to provide them unless macro <code>BOOST_SYSTEM_NO_DEPRECATED</code>
124 <table border="1" cellpadding="5" cellspacing="1" style="border-collapse: collapse" bordercolor="#111111">
126 <td><b><i>Old usage, now deprecated</i></b></td>
127 <td><b><i>Replacement</i></b></td>
130 <td><code>get_generic_category()</code></td>
131 <td><code>generic_category()</code></td>
134 <td><code>get_system_category()</code></td>
135 <td><code>system_category()</code></td>
138 <td><code>namespace posix</code></td>
139 <td><code>namespace errc</code></td>
142 <td><code>namespace posix_error</code></td>
143 <td><code>namespace errc</code></td>
146 <td><code>enum posix_errno</code></td>
147 <td><code>enum errc_t</code></td>
150 <td><code>get_posix_category()</code></td>
151 <td><code>generic_category()</code></td>
154 <td><code>posix_category</code></td>
155 <td><code>generic_category()</code></td>
158 <td><code>errno_ecat</code></td>
159 <td><code>generic_category()</code></td>
162 <td><code>native_ecat</code></td>
163 <td><code>system_category()</code></td>
166 <h2><a name="Breaking-changes">Breaking changes</a></h2>
167 <p>Two static consts are replaced by functions. These are breaking changes best
168 fixed by globally adding () to these names to turn them into function calls.</p>
169 <table border="1" cellpadding="5" cellspacing="1" style="border-collapse: collapse" bordercolor="#111111">
171 <td><b><i>Old usage, now broken</i></b></td>
172 <td><b><i>Replacement</i></b></td>
175 <td><code>generic_category</code></td>
176 <td><code>generic_category()</code></td>
179 <td><code>system_category</code></td>
180 <td><code>system_category()</code></td>
183 <p>User-defined BOOST_POSIX_API and BOOST_WINDOWS_API macros are no longer supported.</p>
184 <h2><a name="Header-error_code">Header <boost/system/error_code.hpp></a></h2>
185 <h3><boost/system/error_code.hpp> synopsis</h3>
191 class <a href="#Class-error_category">error_category</a>;
192 const error_category & <a href="#system_category">system_category</a>() noexcept;
193 const error_category & <a href="#generic_category">generic_category</a>() noexcept;
195 class <a href="#Class-error_code">error_code</a>;
196 class <a href="#Class-error_condition">error_condition</a>;
199 template< class T="" >
200 struct is_error_code_enum { static const bool value = false; };
202 template< class T="" >
203 struct is_error_condition_enum { static const bool value = false; };
205 // generic error_conditions
211 address_family_not_supported, //EAFNOSUPPORT
212 address_in_use, //EADDRINUSE
213 address_not_available, //EADDRNOTAVAIL
214 already_connected, //EISCONN
215 argument_list_too_long, //E2BIG
216 argument_out_of_domain, //EDOM
217 bad_address, //EFAULT
218 bad_file_descriptor, //EBADF
219 bad_message, //EBADMSG
221 connection_aborted, //ECONNABORTED
222 connection_already_in_progress, //EALREADY
223 connection_refused, //ECONNREFUSED
224 connection_reset, //ECONNRESET
225 cross_device_link, //EXDEV
226 destination_address_required, //EDESTADDRREQ
227 device_or_resource_busy, //EBUSY
228 directory_not_empty, //ENOTEMPTY
229 executable_format_error, //ENOEXEC
230 file_exists, //EEXIST
231 file_too_large, //EFBIG
232 filename_too_long, //ENAMETOOLONG
233 function_not_supported, //ENOSYS
234 host_unreachable, //EHOSTUNREACH
235 identifier_removed, //EIDRM
236 illegal_byte_sequence, //EILSEQ
237 inappropriate_io_control_operation,//ENOTTY
239 invalid_argument, //EINVAL
240 invalid_seek, //ESPIPE
242 is_a_directory, //EISDIR
243 message_size, //EMSGSIZE
244 network_down, //ENETDOWN
245 network_reset, //ENETRESET
246 network_unreachable, //ENETUNREACH
247 no_buffer_space, //ENOBUFS
248 no_child_process, //ECHILD
250 no_lock_available, //ENOLCK
251 no_message_available, //ENODATA
253 no_protocol_option, //ENOPROTOOPT
254 no_space_on_device, //ENOSPC
255 no_stream_resources, //ENOSR
256 no_such_device_or_address, //ENXIO
257 no_such_device, //ENODEV
258 no_such_file_or_directory, //ENOENT
259 no_such_process, //ESRCH
260 not_a_directory, //ENOTDIR
261 not_a_socket, //ENOTSOCK
262 not_a_stream, //ENOSTR
263 not_connected, //ENOTCONN
264 not_enough_memory, //ENOMEM
265 not_supported, //ENOTSUP
266 operation_canceled, //ECANCELED
267 operation_in_progress, //EINPROGRESS
268 operation_not_permitted, //EPERM
269 operation_not_supported, //EOPNOTSUPP
270 operation_would_block, //EWOULDBLOCK
271 owner_dead, //EOWNERDEAD
272 permission_denied, //EACCES
273 protocol_error, //EPROTO
274 protocol_not_supported, //EPROTONOSUPPORT
275 read_only_file_system, //EROFS
276 resource_deadlock_would_occur, //EDEADLK
277 resource_unavailable_try_again, //EAGAIN
278 result_out_of_range, //ERANGE
279 state_not_recoverable, //ENOTRECOVERABLE
280 stream_timeout, //ETIME
281 text_file_busy, //ETXTBSY
282 timed_out, //ETIMEDOUT
283 too_many_files_open_in_system, //ENFILE
284 too_many_files_open, //EMFILE
285 too_many_links, //EMLINK
286 too_many_synbolic_link_levels, //ELOOP
287 value_too_large, //EOVERFLOW
288 wrong_protocol_type //EPROTOTYPE
293 template<> struct is_error_condition_enum<posix::posix_errno><errc::errc_t>
294 { static const bool value = true; };
296 // <a href="#Non-member-functions">non-member functions</a>
298 bool operator==( const error_code & lhs, const error_code & rhs ) noexcept;
299 bool operator==( const error_code & code, const error_condition & condition ) noexcept;
300 bool operator==( const error_condition & condition, const error_code & code ) noexcept;
301 bool operator==( const error_condition & lhs, const error_condition & rhs ) noexcept;
303 bool operator!=( const error_code & lhs, const error_code & rhs ) noexcept;
304 bool operator!=( const error_code & code, const error_condition & condition ) noexcept;
305 bool operator!=( const error_condition & condition, const error_code & code ) noexcept;
306 bool operator!=( const error_condition & lhs, const error_condition & rhs ) noexcept;
308 bool operator<( const error_code & lhs, const error_code & rhs ) noexcept;
309 bool operator<( const error_condition & lhs, const error_condition & rhs ) noexcept;
311 error_code make_error_code( errc::errc_t e ) noexcept;
312 error_condition make_error_condition( errc::errc_t e ) noexcept;
314 template <class charT, class traits>
315 std::basic_ostream<charT,traits>&
316 operator<<( basic_ostream<charT,traits>& os, const error_code & ec );
318 size_t hash_value( const error_code & ec );
322 <p>The value of each<code> errc_t</code> constant shall be the same as the
323 value of the <code><cerrno></code> macro shown in the above synopsis.</p>
324 <p>Users may specialize <code>is_error_code_enum</code> and <code>
325 is_error_condition_enum</code> templates to indicate that a type is eligible for
326 class <code>error_code</code> and <code>error_condition</code> automatic
327 conversions respectively.</p>
329 <pre>const error_category & <a name="system_category">system_category</a>();</pre>
331 <p><i>Returns:</i> A reference to a <code>error_category</code> object
332 identifying errors originating from the operating system.</p>
334 <pre>const error_category & <a name="generic_category">generic_category</a>();</pre>
336 <p><i>Returns:</i> A reference to a <code>error_category</code> object
337 identifying portable error conditions.</p>
340 <h2><a name="Class-error_category">Class <code>error_category</code></a></h2>
341 <p>The class <code>error_category</code> defines the base class for types used
342 to identify the source and encoding of a particular category of error code.</p>
343 <p><i>[Note:</i> Classes may be derived from <code>error_category</code>
344 to support additional categories of errors. <i>--end note]</i></p>
345 <p>The class <code>error_category</code> serves as a base class for types used
346 to identify the source and encoding of a particular category of error code.
347 Classes may be derived from <code>error_category</code> to support categories of
348 errors in addition to those defined in the Boost System library. Such classes
349 shall behave as specified in this subclause. [<i> Note:</i> <code>error_category</code>
350 objects are passed by reference, and two such objects are equal if they have the
351 same address. This means that applications using custom <code>error_category</code>
352 types should create a single object of each such type. <i>
\97end note</i> ]</p>
353 <h3><a name="Class-error_category-synopsis">Class <code>error_category</code> synopsis</a></h3>
359 class error_category : public noncopyable
362 virtual ~error_category();
364 virtual const char * name() const noexcept = 0;
365 virtual string message( int ev ) const = 0;
366 virtual error_condition default_error_condition( int ev ) const noexcept;
367 virtual bool equivalent( int code, const error_condition & condition )
369 virtual bool equivalent( const error_code & code, int condition ) const noexcept;
371 bool operator==( const error_category & rhs ) const noexcept;
372 bool operator!=( const error_category & rhs ) const noexcept;
373 bool operator< ( const error_category & rhs ) const noexcept;
378 <h3><a name="Class-error_category-virtual-members">Class <code>error_category</code> virtual members</a></h3>
379 <p>Classes derived from <code>error_category</code> shall behave as specified in
381 <pre>virtual const char * name() const noexcept =0;</pre>
383 <p><i>Returns: </i>a string naming the error category.</p>
385 <pre>virtual string message( int ev ) const noexcept =0;</pre>
387 <p><i>Returns:</i> A string that describes the error denoted by
390 <pre>virtual error_condition default_error_condition( int ev ) const noexcept;</pre>
392 <p><i>Returns:</i> <code>error_condition( ev, *this )</code>.</p>
394 <p dir="ltr"> [<i>--Note:</i> Derived classes will typically convert <code>ev</code>
395 to some portable <code>error_category</code>, such as <code>generic_category()</code>,
396 and return it as an <code>error_condition</code> for that category. <i>--end
400 <pre>virtual bool equivalent( int code, const error_condition & condition ) const noexcept;</pre>
402 <p><i>Returns:</i> <code>default_error_condition( code ) == condition</code>.</p>
404 <pre>virtual bool equivalent( const error_code & code, int condition ) const noexcept;</pre>
406 <p><i>Returns:</i> <code>*this == code.category() && code.value() == condition</code>.</p>
408 <h3><a name="Class-error_category-non-virtual-members">Class <code>error_category</code> non-virtual members</a></h3>
409 <pre>bool operator==( const error_category & rhs ) const noexcept;</pre>
411 <p><i>Returns:</i> <code>this == &rhs</code>.</p>
413 <pre>bool operator!=( const error_category & rhs ) const noexcept;</pre>
415 <p><i>Returns:</i> <code>this != &rhs</code>.</p>
418 <pre>bool operator<( const error_category & rhs ) const noexcept;</pre>
420 <p><i>Returns:</i> <code>std::less<const error_category*>()( this, &rhs
421 noexcept)</code>.</p>
423 <p><i>[Note:</i> <code>std::less</code> provides a total ordering for
424 pointers. <i>--end note]</i></p>
427 <h2><a name="Class-error_code">Class <code>
428 error_code</code></a></h2>
429 <p>The class <code>error_code</code> describes an object used to hold error code
430 values, such as those originating from the operating<br>
431 system or other low-level application program interfaces. <i>[ Note: </i>Class
432 <code>error_code</code> is an adjunct to error reporting by<br>
433 exception. <i>
\97end note ]</i></p>
434 <h3><a name="Class-error_code-synopsis">Class <code>
435 error_code</code> synopsis</a></h3>
445 error_code() noexcept;
446 error_code( val, const error_category & cat ) noexcept;
447 template <class <code>ErrorCodeEnum</code>>
448 error_code(<code> ErrorCodeEnum</code> e ) noexcept;
451 void assign( int val, const error_category & cat ) noexcept;
452 template<typename <code>ErrorCodeEnum</code>>
453 error_code & operator=( <code>ErrorCodeEnum</code> val ) noexcept;
454 void clear() noexcept;
457 int value() const noexcept;
458 cont error_category & category() const noexcept;
459 error_condition default_error_condition() const noexcept;
460 string message() const;
461 operator unspecified-bool-type() const;
464 int val_; // <i>exposition only</i>
465 const error_category * cat_; // <i>exposition only</i>
470 <h3><a name="Class-error_code-constructors">Class <code>
471 error_code</code> constructors</a></h3>
472 <pre>error_code() noexcept;</pre>
474 <p><i>Effects: </i>Constructs an object of type <code>error_code</code>.</p>
475 <p><i>Postconditions:</i> <code>val_ == 0 && cat_ == &system_category()</code>.</p>
477 <pre>error_code( int val, const error_category & cat ) noexcept;</pre>
479 <p><i>Effects: </i>Constructs an object of type <code>error_code</code>.</p>
480 <p><i>Postconditions:</i> <code>val_ == val && cat_ == &cat</code>.</p>
482 <pre>template <class <code>ErrorCodeEnum</code>>
483 error_code(<code> ErrorCodeEnum</code> val ) noexcept;</pre>
485 <p><i>Effects: </i>Constructs an object of type <code>error_code</code>.</p>
486 <p><i>Postconditions:</i> <code>*this == make_error_code( val )</code>.</p>
487 <p><i>Remarks:</i> This constructor shall not participate in overload
488 resolution unless <code>is_error_code_enum<ErrorCodeEnum>::value</code> is
489 <code>true</code>.</p>
491 <h3><a name="Class-error_code-modifiers">Class <code>
492 error_code</code> modifiers</a></h3>
493 <pre>void assign( int val, const error_category & cat ) noexcept;</pre>
495 <p><i>Postconditions:</i> <code>val_ == val && cat_ == &cat</code>.</p>
497 <pre>template<typename <code>ErrorCodeEnum</code>>
498 error_code & operator=( <code>ErrorCodeEnum</code> val ) noexcept;</pre>
500 <p><i>Postconditions:</i> <code>*this == make_error_code( val )</code>.</p>
501 <p><i>Remarks:</i> This operator shall not participate in overload resolution
502 unless <code>is_error_code_enum<ErrorCodeEnum>::value</code> is <code>true</code>.</p>
504 <pre><code>void clear() noexcept;</code></pre>
506 <p><i>postcondition:</i> <code>value() == 0 && category() ==
507 system_category()</code></p>
509 <h3><a name="Class-error_code-observers">Class <code>
510 error_code</code> observers</a></h3>
511 <pre><code>int value() const noexcept;</code></pre>
513 <p><i>Returns:</i> <code>val_</code>.</p>
515 <pre><code>const error_category & category() const noexcept;</code></pre>
517 <p><i>Returns:</i> <code>*cat_</code>.</p>
519 <pre>error_condition default_error_condition() const noexcept;</pre>
521 <p><i>Returns:</i> <code>category().default_error_condition( value())</code>.</p>
523 <pre><code>string message() const;</code></pre>
525 <p><i>Returns:</i> <code>category().message( value())</code>.</p>
526 <p><i>Throws:</i> Nothing.</p>
528 <pre>operator unspecified-bool-type() const;</pre>
530 <p><i>Returns:</i> if <code>value() != 0</code>, returns a value that will evaluate
531 <code>true</code> in a boolean context; otherwise, returns a value that will
532 evaluate <code>false</code> in a boolean context. The value type returned shall
533 not be convertible to <code>int</code>.</p>
534 <p><i>Throws:</i> nothing.</p>
535 <p><i>[Note: </i>This conversion can be used in contexts where a <code>bool</code>
536 is expected ( e.g., an <code>if</code> condition ); however, implicit conversions
537 ( e.g., to <code>int</code>) that can occur with <code>bool</code> are not
538 allowed, eliminating some sources of user error. One possible implementation
539 choice for this type is pointer-to-member. <i>--end note ]</i></p>
541 <h2><a name="Class-error_condition">Class <code>error_condition</code></a></h2>
542 <p>The class <code>error_condition</code> describes an object used to hold
543 values identifying error conditions. <i>[ Note: </i><code>error_condition</code>
544 values are portable abstractions, while <code>error_code</code> values are
545 implementation specific. <i>--end note ]</i></p>
546 <h3><a name="Class-error_condition-synopsis">Class <code>error_condition</code> synopsis</a></h3>
552 class error_condition
557 error_condition() noexcept;
558 error_condition( int val, const error_category & cat ) noexcept;
559 template <class ErrorConditionEnum>
560 error_condition( errorConditionEnum val ) noexcept;
563 void assign( int val, const error_category & cat ) noexcept;
564 template<typename ErrorConditionEnum>
565 error_condition & operator=( ErrorConditionEnum val ) noexcept;
566 void clear() noexcept;
569 int value() const noexcept;
570 const error_category & category() const noexcept;
571 string message() const;
572 operator unspecified-bool-type () const noexcept;
575 int val_; // <i>exposition only</i>
576 const error_category * cat_; // <i>exposition only</i>
581 <h3><a name="Class-error_condition-constructors">Class <code>error_condition</code>
582 constructors</a></h3>
583 <pre>error_condition() noexcept; </pre>
585 <p><i>Effects:</i> Constructs an object of type <code>error_condition</code>.</p>
586 <p><i>Postconditions:</i> <code>val_ == 0 and cat_ == &generic_category()</code>.</p>
588 <pre>error_condition( int val, const error_category & cat ) noexcept;</pre>
590 <p><i>Effects: </i>Constructs an object of type error_condition.</p>
591 <p><i>Postconditions:</i> <code>val_ == val and cat_ == &cat</code>.</p>
593 <pre>template <class ErrorConditionEnum>
594 error_condition( ErrorConditionEnum e ) noexcept;</pre>
596 <p><i>Effects:</i> Constructs an object of type <code>error_condition</code>.</p>
597 <p><i>Postconditions:</i> <code>*this == make_error_condition(e)</code>.</p>
598 <p><i>Remarks:</i> This constructor shall not participate in overload
599 resolution unless <code>is_error_condition_enum<ErrorConditionEnum>::value</code>
600 is <code>true</code>.</p>
602 <h3><a name="Class-error_condition-modifiers">Class <code>error_condition</code>
604 <pre>void assign( int val, const error_category & cat ) noexcept; </pre>
606 <p><i>Postconditions:</i> <code>val_ == val and cat_ == &cat</code>. </p>
608 <pre>template<typename ErrorConditionEnum>
609 error_condition & operator=( ErrorConditionEnum e ) noexcept;</pre>
611 <p><i>Postconditions:</i> <code>*this == make_error_condition( e )</code>.</p>
612 <p><i>Returns:</i> <code>*this</code>.</p>
613 <p><i>Remarks:</i> This operator shall not participate in overload resolution
614 unless <code>is_error_condition_enum<ErrorConditionEnum>::value</code> is
615 <code>true</code>.</p>
617 <pre>void clear() noexcept;</pre>
619 <p><i>Postcondition:</i> <code>value() == 0 && category() == generic_category()</code></p>
621 <h3><a name="Class-error_condition-observers">Class <code>error_condition</code>
623 <pre>int value() const noexcept;</pre>
625 <p><i>Returns:</i> <code>val_</code>.</p>
627 <pre>const error_category & category() const noexcept;</pre>
629 <p><i>Returns:</i> <code>*cat_</code>.</p>
631 <pre>string message() const;</pre>
633 <p><i>Returns:</i> <code>category().message( value() )</code>.</p>
635 <pre>operator unspecified-bool-type () const;</pre>
637 <p><i>Returns: </i>If <code>value() != 0</code>, returns a value that will
638 evaluate <code>true</code> in a boolean context; otherwise, returns a value
639 that will evaluate <code>false</code>. The return type shall not be
640 convertible to <code>int</code>. </p>
641 <p><i>Throws:</i> Nothing.</p>
642 <p><i> [ Note:</i> This conversion can be used in contexts where a <code>bool</code>
643 is expected ( e.g., an if condition ); however, implicit conversions ( e.g., to
644 <code>int</code>) that can occur with <code>bool</code> are not allowed,
645 eliminating some sources of user error. One possible implementation choice for
646 this type is pointer to member. <i>--end note</i> <i>]</i></p>
648 <h2><a name="throws-object"><code>throws</code> object</a></h2>
649 <pre>extern error_code throws;</pre>
650 <p>The predefined <code>error_code</code> object <code>throws</code> is supplied
651 for use as a "throw on error" tag.</p>
652 <h2><a name="Semantics-of-throws">Semantics of <code>throws</code></a> object</h2>
653 <p>Functions that specify an argument in the form <code>error_code& ec=throws</code>,
654 with appropriate namespace qualifiers, have the following error handling
657 <p><i>Postconditions:</i></p>
659 <p>If <code>&ec != &throws</code> and an error occurred:</p>
661 <li> <code>ec.value()</code> returns the implementation specific error
662 number for the particular error that occurred.</li>
663 <li><code>ec.category()</code> returns the <code>
664 <a href="#Class-error_category">error_category</a></code> for <code>ec.value()</code>.</li>
666 <p>if <code>&ec != &throws</code> and an error did not occur, <code>ec.clear()</code>.</p>
668 <p><i>Throws:</i></p>
670 <p>If an error occurs and <code>&ec == &throws</code>, throws an exception of type
671 <code><a href="#Class-system_error">system_error</a></code> or of a type
672 derived from <code><a href="#Class-system_error">system_error</a></code>. The
673 exception's <code>code()</code> member function returns a reference to an
674 <code>error_code</code> object with the behavior specified in <i>
675 Postconditions</i>.</p>
678 <h2><a name="Non-member-functions">Non-member functions</a></h2>
679 <pre>bool operator==( const error_code & lhs, const error_code & rhs ) noexcept;</pre>
681 <p><i>Returns:</i> <code>lhs.category() == rhs.category() && lhs.value() ==
682 rhs.value()</code>.</p>
684 <pre>bool operator==( const error_code & code, const error_condition & condition ) noexcept;
685 bool operator==( const error_condition & condition, const error_code & code ) noexcept;</pre>
687 <p><i>Returns:</i> <code>code.category().equivalent( code.value(), condition )<br>
688 || condition.category().equivalent( code, condition.value() )</code>.</p>
690 <pre>bool operator==( const error_condition & lhs, const error_condition & rhs ) noexcept;</pre>
692 <p><i>Returns:</i> <code>lhs.category() == rhs.category() && lhs.value() ==
693 rhs.value()</code>.</p>
695 <pre>bool operator!=( const error_code & lhs, const error_code & rhs ) noexcept;</pre>
697 <p><i>Returns:</i> <code>!(lhs == rhs )</code>.</p>
699 <pre>bool operator!=( const error_code & code, const error_condition & condition ) noexcept;
700 bool operator!=( const error_condition & condition, const error_code & code ) noexcept;</pre>
702 <p><i>Returns:</i><code> !( code == condition )</code>.</p>
704 <pre>bool operator!=( const error_condition & lhs, const error_condition & rhs ) noexcept;</pre>
706 <p><i>Returns:</i> <code>!(lhs == rhs )</code>.</p>
708 <pre>bool operator<( const error_code & lhs, const error_code & rhs ) noexcept;</pre>
710 <p><i>Returns:</i> <code>lhs.category() < rhs.category()<br>
711 || (lhs.category() == rhs.category() && lhs.value() < rhs.value())</code>.</p>
713 <pre>bool operator<( const error_condition & lhs, const error_condition & rhs ) noexcept;</pre>
715 <p><i>Returns:</i> <code>lhs.category() < rhs.category()<br>
716 || (lhs.category() == rhs.category() && lhs.value() < rhs.value())</code>.</p>
718 <pre>error_code make_error_code( errc::errc_t e ) noexcept;</pre>
720 <p><i>Returns:</i> <code>error_code( e, generic_category())</code>.</p>
722 <pre>error_condition make_error_condition( errc::errc_t e ) noexcept;</pre>
724 <p><i>Returns:</i> <code>error_condition( static_cast<int>( e ), generic_category())</code>.</p>
727 <pre>template <class charT, class traits>
728 std::basic_ostream<charT,traits>&
729 operator<<( basic_ostream<charT,traits>& os, const error_code & ec );</pre>
731 <p><i>Effects:</i> <code>os << ec.category().name() << ':' << ec.value()</code>.</p>
732 <p><i>Returns:</i> <code>os</code>.</p>
734 <pre>size_t <a name="hash_value">hash_value</a>( const error_code & ec );</pre>
736 <p><i>Returns: </i> A hash value representing <code>ec</code>.</p>
739 <h2><a name="Header-system_error">Header <boost/system/system_error.hpp></a></h2>
741 <h3><a name="Class-system_error">Class <code>
742 system_error</code></a></h3>
743 <p>The class <code>system_error</code> describes an exception object used to
744 report errors that have an associated <code><a href="#Class-error_code">error_code</a></code>. Such errors typically originate from operating system or other low-level
745 application program interfaces.</p>
751 class system_error : public std::runtime_error
754 system_error( error_code ec );
755 system_error( error_code ec, const char * what_arg );
756 system_error( error_code ec, const std::string & what_arg );
757 system_error( int ev, const error_category & ecat,
758 const char * what_arg );
759 system_error( int ev, const error_category & ecat,
760 const std::string & what_arg );
761 system_error( int ev, const error_category & ecat);
763 const error_code & code() const throw();
764 const char * what() const throw();
769 <pre>system_error( error_code ec );</pre>
771 <p><i>Effects:</i> Constructs an object of class <code>system_error</code>.</p>
772 <p><i>Postcondition:</i> <code>code() == ec <br>
773 && std::strcmp( this->runtime_error::what(), "" ) == 0</code></p>
775 <pre>system_error( error_code ec, const char * what_arg );</pre>
777 <p><i>Effects:</i> Constructs an object of class <code>system_error</code>.</p>
778 <p><i>Postcondition:</i> <code>code() == ec <br>
779 && std::strcmp( this->runtime_error::what(), what_arg ) == 0</code></p>
781 <pre>system_error( error_code ec, const std::string & what_arg );</pre>
783 <p><i>Effects:</i> Constructs an object of class <code>system_error</code>.</p>
784 <p><i>Postcondition:</i> <code>code() == ec <br>
785 && std::strcmp( this->runtime_error::what(), what_arg.c_str() ) == 0</code></p>
787 <pre>system_error( int ev, const error_category & ecat,
788 const char * what_arg );</pre>
790 <p><i>Effects:</i> Constructs an object of class <code>system_error</code>.</p>
791 <p><i>Postcondition:</i> <code>code() == error_code( ev, ecat )<br>
792 && std::strcmp( this->runtime_error::what(), what_arg ) == 0</code></p>
794 <pre>system_error( int ev, const error_category & ecat,
795 const std::string & what_arg );</pre>
797 <p><i>Effects:</i> Constructs an object of class <code>system_error</code>.</p>
798 <p><i>Postcondition:</i> <code>code() == error_code( ev, ecat )<br>
799 && std::strcmp( this->runtime_error::what(), what_arg.c_str() ) == 0</code></p>
801 <pre>system_error( int ev, const error_category & ecat );</pre>
803 <p><i>Effects:</i> Constructs an object of class <code>system_error</code>.</p>
804 <p><i>Postcondition:</i> <code>code() == error_code( ev, ecat )<br>
805 && std::strcmp( this->runtime_error::what(), "" ) == 0</code></p>
807 <pre>const error_code & code() const;</pre>
809 <p><i>Returns:</i> <code>ec</code> or <code>error_code( ev, ecat )</code>, from
810 the constructor, as appropriate.</p>
812 <pre>const char * what() const;</pre>
814 <p><i>Returns: </i>A string incorporating <code>
815 this->runtime_error::what()</code> and <code>
816 code.message()</code>.</p>
821 <!--webbot bot="Timestamp" S-Type="EDITED" S-Format="%B %d, %Y" startspan -->January 06, 2014<!--webbot bot="Timestamp" endspan i-checksum="31400" --> </font>
824 <p>© Copyright Beman Dawes, 2006, 2007, 2008, 2013</p>
826 <p>Distributed under the Boost Software License, Version 1.0. See
827 <a href="http://www.boost.org/LICENSE_1_0.txt">www.boost.org/LICENSE_1_0.txt</a></p>