std::ios_base::failure(3) | C++ Standard Libary | std::ios_base::failure(3) |
NAME¶
std::ios_base::failure - std::ios_base::failure
Synopsis¶
Defined in header <ios>
class failure;
The class std::ios_base::failure defines an exception object that is thrown
on
failure by the functions in the Input/Output library.
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
(since C++17)
equivalent functionality.
std-ios base-failure-2003-inheritance.svg
(until C++11)
Inheritance diagram
std-ios base-failure-inheritance.svg
(since C++11)
Inheritance diagram
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
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, (1)
const std::error_code& ec = std::io_errc::stream (2) (since
C++11)
);
failure( const failure& other ); (3) (until C++11)
failure( const failure& other ) noexcept; (since C++11)
1-2) Constructs the exception object using 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)
3) Copy constructor. Initialize 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.
(since C++11)
Parameters¶
message - explanatory string
ec - error code to identify the specific reason for the failure
other - another failure to copy
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¶
code returns error code
(public member function of std::system_error)
what returns an explanatory string
[virtual] (virtual public member function of
std::system_error)
Inherited from std::runtime_error
Inherited from std::exception
Member functions¶
destructor destroys the exception object
[virtual] (virtual public member function of std::exception)
what returns an explanatory string
[virtual] (virtual public member function of
std::exception)
Example¶
// Run this code
#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¶
io_errc the IO stream error codes
(C++11) (enum)
2022.07.31 | http://cppreference.com |