# std::bad_optional_access

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< cpp‎ | utility‎ | optional

Defined in header `<optional>` |  |
class bad_optional_access; |  | (since C++17)

Defines a type of object to be thrown by std::optional::value when accessing an optional object that does not contain a value.

Inheritance diagram

### Member functions

(constructor) | constructs a new `bad_optional_access` object (public member function)
operator= | replaces the `bad_optional_access` object (public member function)
what | returns the explanatory string (public member function)

## std::bad_optional_access::bad_optional_access

bad_optional_access() noexcept; | (1) | (since C++17)
bad_optional_access( const bad_optional_access& other ) noexcept; | (2) | (since C++17)

Constructs a new `bad_optional_access` object with an implementation-defined null-terminated byte string which is accessible through `what()`.

1) Default constructor.
2) Copy constructor. If `*this` and `other` both have dynamic type `std::bad_optional_access` then std::strcmp(what(), other.what()) == 0.

### Parameters

other | - | another exception object to copy

## std::bad_optional_access::operator=

bad_optional_access& operator=( const bad_optional_access& other ) noexcept; |  | (since C++17)

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

### Parameters

other | - | another exception object to assign with

### Return value

*this

## std::bad_optional_access::what

virtual const char* what() const noexcept; |  | (since C++17)

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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