std::error_condition

 

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std::error_condition

Member functions

error_condition::error_condition

error_condition::operator=

error_condition::assign

error_condition::clear

error_condition::value

error_condition::category

error_condition::message

error_condition::operator bool

Non-member functions

operator==operator!=operator<operator<=> (until C++20)(until C++20)(C++20)

Helper classes

is_error_condition_enum

hash<std::error_condition>

 

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

See More

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<operator<=> (removed in C++20)(removed in C++20)(C++20)

compares error_conditions and error_codes (function)

Helper classes

is_error_condition_enum (C++11)	identifies an enumeration as an std::error_condition (class template)
std::hash<std::error_condition> (C++17)	hash support for std::error_condition (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 (C++11)	holds a platform-dependent error code (class)
error_category (C++11)	base class for error categories (class)
make_error_condition(std::errc) (C++11)	creates an error condition for an errc value e (function)