Scroll to navigation

std::format_error(3) C++ Standard Libary std::format_error(3)

NAME

std::format_error - std::format_error

Synopsis


Defined in header <format>
class format_error; (since C++20)


Defines the type of exception object thrown to report errors in the formatting
library.


std-format error-inheritance.svg


Inheritance diagram

Member functions


constructor constructs a new format_error object with the given message
(public member function)
operator= replaces the format_error object
(public member function)

std::format_error::format_error


format_error( const std::string& what_arg ); (1)
format_error( const char* what_arg ); (2)
format_error( const format_error& other ) noexcept; (3)


1) Constructs the exception object with what_arg as explanatory string. After
construction, std::strcmp(what(), what_arg.c_str()) == 0.
2) Constructs the exception object with what_arg as explanatory string. After
construction, std::strcmp(what(), what_arg) == 0.
3) Copy constructor. If *this and other both have dynamic type std::format_error
then std::strcmp(what(), other.what()) == 0. No exception can be thrown from the
copy constructor.

Parameters


what_arg - explanatory string
other - another exception object to copy

Exceptions


1,2) May throw std::bad_alloc.

Notes


Because copying std::format_error 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.


A derived standard exception class must have a publicly accessible copy constructor.
It can be implicitly defined as long as the explanatory strings obtained by what()
are the same for the original object and the copied object.

std::format_error::operator=


format_error& operator=( const format_error& other ) noexcept;


Assigns the contents with those of other. If *this and other both have dynamic type
std::format_error then std::strcmp(what(), other.what()) == 0 after assignment. No
exception can be thrown from the copy assignment operator.

Parameters


other - another exception object to assign with

Return value


*this

Notes


A derived standard exception class must have a publicly accessible copy assignment
operator. It can be implicitly defined as long as the explanatory strings obtained
by what() are the same for the original object and the copied object.

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


This section is incomplete
Reason: no example

See also

Category:


* Todo no example

2024.06.10 http://cppreference.com