[syserr.errcondition]

# 19 Diagnostics library [[diagnostics]](./#diagnostics)

## 19.5 System error support [[syserr]](syserr#errcondition)

### 19.5.5 Class error_condition [syserr.errcondition]

#### [19.5.5.1](#overview) Overview [[syserr.errcondition.overview]](syserr.errcondition.overview)

[1](#overview-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L1238)

The class error_condition describes an object used to hold values identifying
error conditions[.](#overview-1.sentence-1)

[*Note [1](#overview-note-1)*:

error_condition values are portable abstractions,
while error_code values ([[syserr.errcode]](syserr.errcode "19.5.4 Class error_­code")) are implementation specific[.](#overview-1.sentence-2)

— *end note*]

[🔗](#lib:error_condition)

namespace std {class error_condition {public:// [[syserr.errcondition.constructors]](#constructors "19.5.5.2 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 "19.5.5.3 Modifiers"), modifiersvoid assign(int val, const error_category& cat) noexcept; template<class ErrorConditionEnum> error_condition& operator=(ErrorConditionEnum e) noexcept; void clear() noexcept; // [[syserr.errcondition.observers]](#observers "19.5.5.4 Observers"), observersint 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) Constructors [[syserr.errcondition.constructors]](syserr.errcondition.constructors)

[🔗](#lib:error_condition,constructor)

`error_condition() noexcept;
`

[1](#constructors-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L1284)

*Effects*: Initializes *val_* with 0 and *cat_* with &generic_category()[.](#constructors-1.sentence-1)

[🔗](#lib:error_condition,constructor_)

`error_condition(int val, const error_category& cat) noexcept;
`

[2](#constructors-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L1296)

*Effects*: Initializes *val_* with val and *cat_* with &cat[.](#constructors-2.sentence-1)

[🔗](#lib:error_condition,constructor__)

`template<class ErrorConditionEnum>
  error_condition(ErrorConditionEnum e) noexcept;
`

[3](#constructors-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L1309)

*Constraints*: is_error_condition_enum_v<ErrorConditionEnum> is true[.](#constructors-3.sentence-1)

[4](#constructors-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L1313)

*Effects*: Equivalent to:error_condition ec = make_error_condition(e);
assign(ec.value(), ec.category());

#### [19.5.5.3](#modifiers) Modifiers [[syserr.errcondition.modifiers]](syserr.errcondition.modifiers)

[🔗](#lib:assign,error_condition)

`void assign(int val, const error_category& cat) noexcept;
`

[1](#modifiers-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L1331)

*Postconditions*: *val_* == val and *cat_* == &cat[.](#modifiers-1.sentence-1)

[🔗](#lib:operator=,error_condition)

`template<class ErrorConditionEnum>
  error_condition& operator=(ErrorConditionEnum e) noexcept;
`

[2](#modifiers-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L1343)

*Constraints*: is_error_condition_enum_v<ErrorConditionEnum> is true[.](#modifiers-2.sentence-1)

[3](#modifiers-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L1347)

*Effects*: Equivalent to:error_condition ec = make_error_condition(e);
assign(ec.value(), ec.category());

[4](#modifiers-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L1355)

*Returns*: *this[.](#modifiers-4.sentence-1)

[🔗](#lib:clear,error_condition)

`void clear() noexcept;
`

[5](#modifiers-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L1366)

*Postconditions*: value() == 0 and category() == generic_category()[.](#modifiers-5.sentence-1)

#### [19.5.5.4](#observers) Observers [[syserr.errcondition.observers]](syserr.errcondition.observers)

[🔗](#lib:value,error_condition)

`int value() const noexcept;
`

[1](#observers-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L1379)

*Returns*: *val_*[.](#observers-1.sentence-1)

[🔗](#lib:category,error_condition)

`const error_category& category() const noexcept;
`

[2](#observers-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L1390)

*Returns*: **cat_*[.](#observers-2.sentence-1)

[🔗](#lib:message,error_condition)

`string message() const;
`

[3](#observers-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L1401)

*Returns*: category().message(value())[.](#observers-3.sentence-1)

[🔗](#lib:operator_bool,error_condition)

`explicit operator bool() const noexcept;
`

[4](#observers-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L1412)

*Returns*: value() != 0[.](#observers-4.sentence-1)

#### [19.5.5.5](#nonmembers) Non-member functions [[syserr.errcondition.nonmembers]](syserr.errcondition.nonmembers)

[🔗](#lib:make_error_condition,errc)

`error_condition make_error_condition(errc e) noexcept;
`

[1](#nonmembers-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/diagnostics.tex#L1425)

*Returns*: error_condition(static_cast<int>(e), generic_category())[.](#nonmembers-1.sentence-1)