[ios.failure]

# 31 Input/output library [[input.output]](./#input.output)

## 31.5 Iostreams base classes [[iostreams.base]](iostreams.base#ios.failure)

### 31.5.2 Class ios_base [[ios.base]](ios.base#ios.failure)

#### 31.5.2.2 Types [[ios.types]](ios.types#ios.failure)

#### 31.5.2.2.1 Class ios_base​::​failure [ios.failure]

[🔗](#lib:ios_base::failure)

namespace std {class ios_base::failure : public system_error {public:explicit failure(const string& msg, const error_code& ec = io_errc::stream); explicit failure(const char* msg, const error_code& ec = io_errc::stream); };}

[1](#1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L919)

An implementation is permitted to define ios_base​::​failure as a synonym for a class with equivalent functionality
to class ios_base​::​failure shown in this subclause[.](#1.sentence-1)

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

When ios_base​::​failure is a synonym for another type,
that type needs to provide a nested type failure to emulate the injected-class-name[.](#1.sentence-2)

— *end note*]

The classfailure defines the base class
for the types of all objects thrown as exceptions,
by functions in the iostreams library,
to report errors detected during stream buffer operations[.](#1.sentence-3)

[2](#2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L935)

When throwing ios_base​::​failure exceptions, implementations should provide
values of ec that identify the specific reason for the failure[.](#2.sentence-1)

[*Note [2](#note-2)*:

Errors arising from the operating system would typically be reported assystem_category() errors with an error value of the error number
reported by the operating system[.](#2.sentence-2)

Errors arising from within the stream library would
typically be reported as error_code(io_errc​::​stream,
iostream_category())[.](#2.sentence-3)

— *end note*]

[🔗](#lib:ios_base::failure,constructor)

`explicit failure(const string& msg, const error_code& ec = io_errc::stream);
`

[3](#3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L952)

*Effects*: Constructs the base class with msg and ec[.](#3.sentence-1)

[🔗](#lib:ios_base::failure,constructor_)

`explicit failure(const char* msg, const error_code& ec = io_errc::stream);
`

[4](#4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/iostreams.tex#L963)

*Effects*: Constructs the base class with msg and ec[.](#4.sentence-1)