std::error_code::assign - cppreference.com

void assign( int val, const error_category& cat ) noexcept;		(since C++11)

Replaces the contents with error code value val and corresponding category cat.

val	-	platform-dependent error code value to assign
cat	-	error category corresponding to `val`

(none)

Compiler support
Freestanding and hosted
Language
Standard library
Standard library headers
Named requirements
Feature test macros (C++20)
Language support library
Concepts library (C++20)
Diagnostics library
Memory management library
Metaprogramming library (C++11)
General utilities library
Containers library
Iterators library
Ranges library (C++20)
Algorithms library
Strings library
Text processing library
Numerics library
Date and time library
Input/output library
Filesystem library (C++17)
Concurrency support library (C++11)
Execution control library (C++26)
Technical specifications
Symbols index
External libraries

Member functions
error_code::error_code
error_code::operator=
error_code::assign
Modifiers
error_code::clear
Observers
error_code::value
error_code::category
error_code::default_error_condition
error_code::message
error_code::operator bool
Non-member functions
operator==operator!=operator<operator<=> (until C++20)(until C++20)(C++20)
operator<<
Helper classes
is_error_code_enum
hash<std::error_code>