1// <system_error> -*- C++ -*-
2
3// Copyright (C) 2007-2020 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library.  This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file include/system_error
26 *  This is a Standard C++ Library header.
27 */
28
29#ifndef _GLIBCXX_SYSTEM_ERROR
30#define _GLIBCXX_SYSTEM_ERROR 1
31
32#pragma GCC system_header
33
34#if __cplusplus < 201103L
35# include <bits/c++0x_warning.h>
36#else
37
38#include <bits/c++config.h>
39#include <bits/error_constants.h>
40#include <iosfwd>
41#include <stdexcept>
42#if __cplusplus > 201703L
43# include <compare>
44#endif
45
46namespace std _GLIBCXX_VISIBILITY(default)
47{
48_GLIBCXX_BEGIN_NAMESPACE_VERSION
49
50  /** @addtogroup diagnostics
51   *  @{
52   */
53
54  class error_code;
55  class error_condition;
56  class system_error;
57
58  /// is_error_code_enum
59  template<typename _Tp>
60    struct is_error_code_enum : public false_type { };
61
62  /// is_error_condition_enum
63  template<typename _Tp>
64    struct is_error_condition_enum : public false_type { };
65
66  template<>
67    struct is_error_condition_enum<errc>
68    : public true_type { };
69
70#if __cplusplus > 201402L
71  template <typename _Tp>
72    inline constexpr bool is_error_code_enum_v =
73      is_error_code_enum<_Tp>::value;
74  template <typename _Tp>
75    inline constexpr bool is_error_condition_enum_v =
76      is_error_condition_enum<_Tp>::value;
77#endif // C++17
78  inline namespace _V2 {
79
80  /** Abstract base class for types defining a category of error codes.
81   *
82   * An error category defines a context that give meaning to the integer
83   * stored in an `error_code` or `error_condition` object. For example,
84   * the standard `errno` constants such a `EINVAL` and `ENOMEM` are
85   * associated with the "generic" category and other OS-specific error
86   * numbers are associated with the "system" category, but a user-defined
87   * category might give different meanings to the same numerical values.
88   */
89  class error_category
90  {
91  public:
92    constexpr error_category() noexcept = default;
93
94    virtual ~error_category();
95
96    error_category(const error_category&) = delete;
97    error_category& operator=(const error_category&) = delete;
98
99    virtual const char*
100    name() const noexcept = 0;
101
102    // We need two different virtual functions here, one returning a
103    // COW string and one returning an SSO string. Their positions in the
104    // vtable must be consistent for dynamic dispatch to work, but which one
105    // the name "message()" finds depends on which ABI the caller is using.
106#if _GLIBCXX_USE_CXX11_ABI
107  private:
108    _GLIBCXX_DEFAULT_ABI_TAG
109    virtual __cow_string
110    _M_message(int) const;
111
112  public:
113    _GLIBCXX_DEFAULT_ABI_TAG
114    virtual string
115    message(int) const = 0;
116#else
117    virtual string
118    message(int) const = 0;
119
120  private:
121    virtual __sso_string
122    _M_message(int) const;
123#endif
124
125  public:
126    virtual error_condition
127    default_error_condition(int __i) const noexcept;
128
129    virtual bool
130    equivalent(int __i, const error_condition& __cond) const noexcept;
131
132    virtual bool
133    equivalent(const error_code& __code, int __i) const noexcept;
134
135    bool
136    operator==(const error_category& __other) const noexcept
137    { return this == &__other; }
138
139#if __cpp_lib_three_way_comparison
140    strong_ordering
141    operator<=>(const error_category& __rhs) const noexcept
142    { return std::compare_three_way()(this, &__rhs); }
143#else
144    bool
145    operator!=(const error_category& __other) const noexcept
146    { return this != &__other; }
147
148    bool
149    operator<(const error_category& __other) const noexcept
150    { return less<const error_category*>()(this, &__other); }
151#endif
152  };
153
154  // DR 890.
155
156  /// Error category for `errno` error codes.
157  _GLIBCXX_CONST const error_category& generic_category() noexcept;
158
159  /// Error category for other error codes defined by the OS.
160  _GLIBCXX_CONST const error_category& system_category() noexcept;
161
162  } // end inline namespace
163
164  error_code make_error_code(errc) noexcept;
165
166  /** Class error_code
167   *
168   * This class is a value type storing an integer error number and a
169   * category that gives meaning to the error number. Typically this is done
170   * close the the point where the error happens, to capture the original
171   * error value.
172   *
173   * An `error_code` object can be used to store the original error value
174   * emitted by some subsystem, with a category relevant to the subsystem.
175   * For example, errors from POSIX library functions can be represented by
176   * an `errno` value and the "generic" category, but errors from an HTTP
177   * library might be represented by an HTTP response status code (e.g. 404)
178   * and a custom category defined by the library.
179   */
180  struct error_code
181  {
182    error_code() noexcept
183    : _M_value(0), _M_cat(&system_category()) { }
184
185    error_code(int __v, const error_category& __cat) noexcept
186    : _M_value(__v), _M_cat(&__cat) { }
187
188    template<typename _ErrorCodeEnum, typename = typename
189	     enable_if<is_error_code_enum<_ErrorCodeEnum>::value>::type>
190      error_code(_ErrorCodeEnum __e) noexcept
191      { *this = make_error_code(__e); }
192
193    void
194    assign(int __v, const error_category& __cat) noexcept
195    {
196      _M_value = __v;
197      _M_cat = &__cat;
198    }
199
200    void
201    clear() noexcept
202    { assign(0, system_category()); }
203
204    // DR 804.
205    template<typename _ErrorCodeEnum>
206      typename enable_if<is_error_code_enum<_ErrorCodeEnum>::value,
207			 error_code&>::type
208      operator=(_ErrorCodeEnum __e) noexcept
209      { return *this = make_error_code(__e); }
210
211    int
212    value() const noexcept { return _M_value; }
213
214    const error_category&
215    category() const noexcept { return *_M_cat; }
216
217    error_condition
218    default_error_condition() const noexcept;
219
220    _GLIBCXX_DEFAULT_ABI_TAG
221    string
222    message() const
223    { return category().message(value()); }
224
225    explicit operator bool() const noexcept
226    { return _M_value != 0; }
227
228    // DR 804.
229  private:
230    int            		_M_value;
231    const error_category* 	_M_cat;
232  };
233
234  // 19.4.2.6 non-member functions
235
236  /// @relates error_code @{
237
238  inline error_code
239  make_error_code(errc __e) noexcept
240  { return error_code(static_cast<int>(__e), generic_category()); }
241
242#if __cpp_lib_three_way_comparison
243  inline strong_ordering
244  operator<=>(const error_code& __lhs, const error_code& __rhs) noexcept
245  {
246    if (auto __c = __lhs.category() <=> __rhs.category(); __c != 0)
247      return __c;
248    return __lhs.value() <=> __rhs.value();
249  }
250#else
251  inline bool
252  operator<(const error_code& __lhs, const error_code& __rhs) noexcept
253  {
254    return (__lhs.category() < __rhs.category()
255	    || (__lhs.category() == __rhs.category()
256		&& __lhs.value() < __rhs.value()));
257  }
258#endif
259
260  template<typename _CharT, typename _Traits>
261    basic_ostream<_CharT, _Traits>&
262    operator<<(basic_ostream<_CharT, _Traits>& __os, const error_code& __e)
263    { return (__os << __e.category().name() << ':' << __e.value()); }
264
265  /// @}
266
267  error_condition make_error_condition(errc) noexcept;
268
269  /** Class error_condition
270   *
271   * This class represents error conditions that may be visible at an API
272   * boundary. Different `error_code` values that can occur within a library
273   * or module might map to the same `error_condition`.
274   *
275   * An `error_condition` represents something that the program can test for,
276   * and subsequently take appropriate action.
277   */
278  struct error_condition
279  {
280    error_condition() noexcept
281    : _M_value(0), _M_cat(&generic_category()) { }
282
283    error_condition(int __v, const error_category& __cat) noexcept
284    : _M_value(__v), _M_cat(&__cat) { }
285
286    template<typename _ErrorConditionEnum, typename = typename
287	 enable_if<is_error_condition_enum<_ErrorConditionEnum>::value>::type>
288      error_condition(_ErrorConditionEnum __e) noexcept
289      { *this = make_error_condition(__e); }
290
291    void
292    assign(int __v, const error_category& __cat) noexcept
293    {
294      _M_value = __v;
295      _M_cat = &__cat;
296    }
297
298    // DR 804.
299    template<typename _ErrorConditionEnum>
300      typename enable_if<is_error_condition_enum
301			 <_ErrorConditionEnum>::value, error_condition&>::type
302      operator=(_ErrorConditionEnum __e) noexcept
303      { return *this = make_error_condition(__e); }
304
305    void
306    clear() noexcept
307    { assign(0, generic_category()); }
308
309    // 19.4.3.4 observers
310    int
311    value() const noexcept { return _M_value; }
312
313    const error_category&
314    category() const noexcept { return *_M_cat; }
315
316    _GLIBCXX_DEFAULT_ABI_TAG
317    string
318    message() const
319    { return category().message(value()); }
320
321    explicit operator bool() const noexcept
322    { return _M_value != 0; }
323
324    // DR 804.
325  private:
326    int 			_M_value;
327    const error_category* 	_M_cat;
328  };
329
330  // 19.4.3.6 non-member functions
331
332  /// Create an `error_condition` representing a standard `errc` condition.
333  /// @relates error_condition
334  inline error_condition
335  make_error_condition(errc __e) noexcept
336  { return error_condition(static_cast<int>(__e), generic_category()); }
337
338  // 19.4.4 Comparison operators
339
340  /// @relates error_code
341  inline bool
342  operator==(const error_code& __lhs, const error_code& __rhs) noexcept
343  { return (__lhs.category() == __rhs.category()
344	    && __lhs.value() == __rhs.value()); }
345
346  /// @relates error_code
347  /// @relates error_condition
348  inline bool
349  operator==(const error_code& __lhs, const error_condition& __rhs) noexcept
350  {
351    return (__lhs.category().equivalent(__lhs.value(), __rhs)
352	    || __rhs.category().equivalent(__lhs, __rhs.value()));
353  }
354
355  /// @relates error_condition
356  inline bool
357  operator==(const error_condition& __lhs,
358	     const error_condition& __rhs) noexcept
359  {
360    return (__lhs.category() == __rhs.category()
361	    && __lhs.value() == __rhs.value());
362  }
363
364#if __cpp_lib_three_way_comparison
365  /// Define an ordering for error_condition objects.
366  /// @relates error_condition
367  inline strong_ordering
368  operator<=>(const error_condition& __lhs,
369	      const error_condition& __rhs) noexcept
370  {
371    if (auto __c = __lhs.category() <=> __rhs.category(); __c != 0)
372      return __c;
373    return __lhs.value() <=> __rhs.value();
374  }
375#else
376  /// Define an ordering for error_condition objects.
377  /// @relates error_condition
378  inline bool
379  operator<(const error_condition& __lhs,
380	    const error_condition& __rhs) noexcept
381  {
382    return (__lhs.category() < __rhs.category()
383	    || (__lhs.category() == __rhs.category()
384		&& __lhs.value() < __rhs.value()));
385  }
386
387  /// @relates error_code
388  /// @relates error_condition
389  inline bool
390  operator==(const error_condition& __lhs, const error_code& __rhs) noexcept
391  {
392    return (__rhs.category().equivalent(__rhs.value(), __lhs)
393	    || __lhs.category().equivalent(__rhs, __lhs.value()));
394  }
395
396  /// @relates error_code
397  inline bool
398  operator!=(const error_code& __lhs, const error_code& __rhs) noexcept
399  { return !(__lhs == __rhs); }
400
401  /// @relates error_code
402  /// @relates error_condition
403  inline bool
404  operator!=(const error_code& __lhs, const error_condition& __rhs) noexcept
405  { return !(__lhs == __rhs); }
406
407  /// @relates error_code
408  /// @relates error_condition
409  inline bool
410  operator!=(const error_condition& __lhs, const error_code& __rhs) noexcept
411  { return !(__lhs == __rhs); }
412
413  /// @relates error_condition
414  inline bool
415  operator!=(const error_condition& __lhs,
416	     const error_condition& __rhs) noexcept
417  { return !(__lhs == __rhs); }
418#endif // three_way_comparison
419
420  /**
421   * @brief An exception type that includes an `error_code` value.
422   *
423   * Typically used to report errors from the operating system and other
424   * low-level APIs.
425   *
426   * @ingroup exceptions
427   */
428  class system_error : public std::runtime_error
429  {
430  private:
431    error_code 	_M_code;
432
433  public:
434    system_error(error_code __ec = error_code())
435    : runtime_error(__ec.message()), _M_code(__ec) { }
436
437    system_error(error_code __ec, const string& __what)
438    : runtime_error(__what + ": " + __ec.message()), _M_code(__ec) { }
439
440    system_error(error_code __ec, const char* __what)
441    : runtime_error(__what + (": " + __ec.message())), _M_code(__ec) { }
442
443    system_error(int __v, const error_category& __ecat, const char* __what)
444    : system_error(error_code(__v, __ecat), __what) { }
445
446    system_error(int __v, const error_category& __ecat)
447    : runtime_error(error_code(__v, __ecat).message()),
448      _M_code(__v, __ecat) { }
449
450    system_error(int __v, const error_category& __ecat, const string& __what)
451    : runtime_error(__what + ": " + error_code(__v, __ecat).message()),
452      _M_code(__v, __ecat) { }
453
454#if __cplusplus >= 201103L
455    system_error (const system_error &) = default;
456    system_error &operator= (const system_error &) = default;
457#endif
458
459    virtual ~system_error() noexcept;
460
461    const error_code&
462    code() const noexcept { return _M_code; }
463  };
464
465_GLIBCXX_END_NAMESPACE_VERSION
466} // namespace
467
468#include <bits/functional_hash.h>
469
470namespace std _GLIBCXX_VISIBILITY(default)
471{
472_GLIBCXX_BEGIN_NAMESPACE_VERSION
473
474#ifndef _GLIBCXX_COMPATIBILITY_CXX0X
475  // DR 1182.
476  /// std::hash specialization for error_code.
477  /// @relates error_code
478  template<>
479    struct hash<error_code>
480    : public __hash_base<size_t, error_code>
481    {
482      size_t
483      operator()(const error_code& __e) const noexcept
484      {
485	const size_t __tmp = std::_Hash_impl::hash(__e.value());
486	return std::_Hash_impl::__hash_combine(&__e.category(), __tmp);
487      }
488    };
489#endif // _GLIBCXX_COMPATIBILITY_CXX0X
490
491#if __cplusplus >= 201703L
492  // DR 2686.
493  /// std::hash specialization for error_condition.
494  /// @relates error_condition
495  template<>
496    struct hash<error_condition>
497    : public __hash_base<size_t, error_condition>
498    {
499      size_t
500      operator()(const error_condition& __e) const noexcept
501      {
502	const size_t __tmp = std::_Hash_impl::hash(__e.value());
503	return std::_Hash_impl::__hash_combine(&__e.category(), __tmp);
504      }
505    };
506#endif
507
508_GLIBCXX_END_NAMESPACE_VERSION
509} // namespace
510
511#endif // C++11
512
513#endif // _GLIBCXX_SYSTEM_ERROR
514