std::ios_base::failure
| Defined in header <ios>
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| class failure; |
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The class std::ios_base::failure defines an exception object that is thrown on failure by the functions in the Input/Output library.
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std::ios_base::failure may be defined either as a member class of std::ios_base or as a synonym (typedef) for another class with equivalent functionality. |
(since C++17) |
 Inheritance diagram |
(until C++11) |
 Inheritance diagram |
(since C++11) |
Member functions
| (constructor) |
constructs a new failure object with the given message (public member function) |
| operator= |
replaces the failure object (public member function) |
| what |
returns the explanatory string (public member function) |
std::ios_base::failure::failure
| (1) | ||
| explicit failure( const std::string& message ); |
(until C++11) | |
| explicit failure( const std::string& message, const std::error_code& ec = std::io_errc::stream ); |
(since C++11) | |
| explicit failure( const char* message, const std::error_code& ec = std::io_errc::stream ); |
(2) | (since C++11) |
| (3) | ||
| failure( const failure& other ); |
(until C++11) | |
| failure( const failure& other ) noexcept; |
(since C++11) | |
message as explanation string which can later be retrieved using what(). ec is used to identify the specific reason for the failure. (since C++11)other. If *this and other both have dynamic type std::ios_base::failure then std::strcmp(what(), other.what()) == 0. (since C++11)Parameters
| message | - | explanatory string |
| ec | - | error code to identify the specific reason for the failure |
| other | - | another failure to copy
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Notes
Because copying std::ios_base::failure is not permitted to throw exceptions, this message is typically stored internally as a separately-allocated reference-counted string. This is also why there is no constructor taking std::string&&: it would have to copy the content anyway.
std::ios_base::failure::operator=
| failure& operator=( const failure& other ); |
(until C++11) | |
| failure& operator=( const failure& other ) noexcept; |
(since C++11) | |
Assigns the contents with those of other. If *this and other both have dynamic type std::ios_base::failure then std::strcmp(what(), other.what()) == 0 after assignment. (since C++11)
Parameters
| other | - | another exception object to assign with |
Return value
*this
std::ios_base::failure::what
| virtual const char* what() const throw(); |
(until C++11) | |
| virtual const char* what() const noexcept; |
(since C++11) | |
Returns the explanatory string.
Parameters
(none)
Return value
Pointer to a null-terminated string with explanatory information. The string is suitable for conversion and display as a std::wstring. The pointer is guaranteed to be valid at least until the exception object from which it is obtained is destroyed, or until a non-const member function (e.g. copy assignment operator) on the exception object is called.
Notes
Implementations are allowed but not required to override what().
Inherited from std::system_error
Member functions
| returns error code (public member function of std::system_error) | |
| [virtual] |
returns an explanatory string (virtual public member function of std::system_error) |
Inherited from std::runtime_error
Inherited from std::exception
Member functions
| [virtual] |
destroys the exception object (virtual public member function of std::exception) |
| [virtual] |
returns an explanatory string (virtual public member function of std::exception) |
Example
#include <iostream> #include <fstream> int main() { std::ifstream f("doesn't exist"); try { f.exceptions(f.failbit); } catch (const std::ios_base::failure& e) { std::cout << "Caught an ios_base::failure.\n" << "Explanatory string: " << e.what() << '\n' << "Error code: " << e.code() << '\n'; } }
Possible output:
Caught an ios_base::failure. Explanatory string: ios_base::clear: unspecified iostream_category error Error code: iostream:1
See also
| (C++11) |
the IO stream error codes (enum) |