NAME¶

std::error_condition - std::error_condition

Synopsis¶

Defined in header <system_error>
class error_condition; (since C++11)

std::error_condition holds a platform-independent value identifying an error
condition. Like std::error_code, it is uniquely identified by an integer value and a
std::error_category, but unlike std::error_code, the value is not
platform-dependent.

A typical implementation holds one integer data member (the value) and a pointer to
an std::error_category.

Member functions¶

constructor constructs an error_condition
(public member function)
operator= replaces the contents
(public member function)
assign replaces the contents
(public member function)
clear sets the error_condition to value 0 in generic_category
(public member function)
value obtains the value of the error_condition
(public member function)
category obtains the error_category for this error_condition
(public member function)
message obtains the explanatory string
(public member function)
operator bool checks if the value is non-zero
(public member function)

Non-member functions¶

operator==
operator!=
operator< compares error_conditions and error_codes
operator<=> (function)
(removed in C++20)
(removed in C++20)
(C++20)

Helper classes¶

is_error_condition_enum identifies an enumeration as an std::error_condition
(C++11) (class template)
std::hash<std::error_condition> hash support for std::error_condition
(C++17) (class template specialization)

Notes¶

The comparison between a std::error_code and a std::error_condition is defined by
their error categories. Notably, an error condition of std::generic_category may
compare equal to an error code of a specific category (e.g. std::system_category),
if they represent the same kind of error.

A std::errc value can be compared to an error code via implicit conversion to
std::error_condition.

// Run this code

#include <cerrno>
#include <iostream>
#include <system_error>
#include <Windows.h>

int main()
{
std::error_code ec{ERROR_FILE_EXISTS, std::system_category()};
std::error_condition econd{EEXIST, std::generic_category()};

std::cout.setf(std::ios::boolalpha);
std::cout << (ec == econd) << '\n'; // typically true
std::cout << (ec == std::errc::file_exists) << '\n'; // ditto
std::cout << (ec == make_error_code(std::errc::file_exists)) << '\n'; // false:
// different category
}

Possible output:¶

true
true
false

See also¶

error_code holds a platform-dependent error code
(C++11) (class)
error_category base class for error categories
(C++11) (class)
make_error_condition(std::errc) creates an error condition for an errc value e
(C++11) (function)