std::ios_base::failure
Defined in header <ios> |
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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.
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(since C++17) |
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Inheritance diagram. |
(until C++11) |
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Inheritance diagram. |
(since C++11) |
Member functions
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(constructor)
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constructs a new failure object with the given message (public member function) |
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operator=
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replaces the failure object (public member function) |
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what
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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 |
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) |
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[virtual]
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returns an explanatory string (virtual public member function of std::system_error) |
Inherited from std::runtime_error
Inherited from std::exception
Member functions
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[virtual]
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destroys the exception object (virtual public member function of std::exception) |
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[virtual]
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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';
}
}
Output:
Caught an ios_base::failure. Explanatory string: ios_base::clear: unspecified iostream_category error Error code: iostream:1
See also
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(C++11)
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the IO stream error codes (enum) |
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https://en.cppreference.com/w/cpp/io/ios_base/failure
