19 Diagnostics library [diagnostics]

19.5 System error support [syserr]

19.5.5 Class error_condition [syserr.errcondition]

19.5.5.1 Overview [syserr.errcondition.overview]

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The class error_condition describes an object used to hold values identifying error conditions.
[Note 1: 
error_condition values are portable abstractions, while error_code values ([syserr.errcode]) are implementation specific.
— end note]
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namespace std { class error_condition { public: // [syserr.errcondition.constructors], constructors error_condition() noexcept; error_condition(int val, const error_category& cat) noexcept; template<class ErrorConditionEnum> error_condition(ErrorConditionEnum e) noexcept; // [syserr.errcondition.modifiers], modifiers void assign(int val, const error_category& cat) noexcept; template<class ErrorConditionEnum> error_condition& operator=(ErrorConditionEnum e) noexcept; void clear() noexcept; // [syserr.errcondition.observers], observers int value() const noexcept; const error_category& category() const noexcept; string message() const; explicit operator bool() const noexcept; private: int val_; // exposition only const error_category* cat_; // exposition only }; }

19.5.5.2 Constructors [syserr.errcondition.constructors]

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error_condition() noexcept;
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Effects: Initializes val_ with 0 and cat_ with &generic_category().
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error_condition(int val, const error_category& cat) noexcept;
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Effects: Initializes val_ with val and cat_ with &cat.
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template<class ErrorConditionEnum> error_condition(ErrorConditionEnum e) noexcept;
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Constraints: is_error_condition_enum_v<ErrorConditionEnum> is true.
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Effects: Equivalent to: error_condition ec = make_error_condition(e); assign(ec.value(), ec.category());

19.5.5.3 Modifiers [syserr.errcondition.modifiers]

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void assign(int val, const error_category& cat) noexcept;
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Postconditions: val_ == val and cat_ == &cat.
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template<class ErrorConditionEnum> error_condition& operator=(ErrorConditionEnum e) noexcept;
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Constraints: is_error_condition_enum_v<ErrorConditionEnum> is true.
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Effects: Equivalent to: error_condition ec = make_error_condition(e); assign(ec.value(), ec.category());
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Returns: *this.
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void clear() noexcept;
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Postconditions: value() == 0 and category() == generic_category().

19.5.5.4 Observers [syserr.errcondition.observers]

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int value() const noexcept;
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Returns: val_.
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const error_category& category() const noexcept;
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Returns: *cat_.
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string message() const;
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Returns: category().message(value()).
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explicit operator bool() const noexcept;
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Returns: value() != 0.

19.5.5.5 Non-member functions [syserr.errcondition.nonmembers]

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error_condition make_error_condition(errc e) noexcept;
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Returns: error_condition(static_cast<int>(e), generic_category()).