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std::runtime_error

Defined in header `<stdexcept>`
class runtime_error;

Defines a type of object to be thrown as exception. It reports errors that are due to events beyond the scope of the program and can not be easily predicted.

Exceptions of type std::runtime_error are thrown by the following standard library components: std::locale::locale and std::locale::combine.

In addition, the following standard exception types are derived from std::runtime_error:

std::regex_error
std::system_error

(since C++11)

std::chrono::ambiguous_local_time
std::chrono::nonexistent_local_time
std::format_error

(since C++20)

Inheritance diagram.

Member functions

(constructor)	constructs a new `runtime_error` object with the given message (public member function)
operator=	replaces the `runtime_error` object (public member function)
what	returns the explanatory string (public member function)

std::runtime_error::runtime_error

runtime_error( const std::string& what_arg );	(1)
runtime_error( const char* what_arg );	(2)	(since C++11)
	(3)
runtime_error( const runtime_error& other );		(until C++11)
runtime_error( const runtime_error& other ) noexcept;		(since C++11)

1-2) Constructs the exception object with what_arg as explanatory string that can be accessed through what().

3) Copy constructor. If *this and other both have dynamic type std::runtime_error then std::strcmp(what(), other.what()) == 0. (since C++11)

Parameters

what_arg	-	explanatory string
other	-	another exception object to copy

Exceptions

1-2) May throw std::bad_alloc

Notes

Because copying std::runtime_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.

std::runtime_error::operator=

runtime_error& operator=( const runtime_error& other );		(until C++11)
runtime_error& operator=( const runtime_error& other ) noexcept;		(since C++11)

Assigns the contents with those of other. If *this and other both have dynamic type std::runtime_error then std::strcmp(what(), other.what()) == 0 after assignment. (since C++11).

Parameters

other

another exception object to assign with

Return value

*this.

std::runtime_error::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::exception

Member functions

(destructor) [virtual]	destroys the exception object (virtual public member function of `std::exception`)
what [virtual]	returns an explanatory string (virtual public member function of `std::exception`)

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