std::bad_function_call

 

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Defined in header <functional>
class bad_function_call;

std::bad_function_call is the type of the exception thrown by std::function::operator() if the function wrapper has no target.

Inheritance diagram

Member functions

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

std::bad_function_call::bad_function_call

bad_function_call() noexcept;	(1)	(since C++11)
bad_function_call( const bad_function_call& other ) noexcept;	(2)	(since C++11)

Constructs a new bad_function_call 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_function_call then std::strcmp(what(), other.what()) == 0.

Parameters

other

-

another exception object to copy

std::bad_function_call::operator=

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

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

Parameters

other

-

another exception object to assign with

Return value

*this

std::bad_function_call::what

virtual const char* what() const noexcept;		(since C++11)

Returns the explanatory string.

Return value

Pointer to an implementation-defined 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.

The returned string is encoded with the ordinary literal encoding during constant evaluation.

(since C++26)

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)

Example

Run this code

#include <functional>
#include <iostream>
 
int main()
{
    std::function<int()> f = nullptr;
    try
    {
        f();
    }
    catch (const std::bad_function_call& e)
    {
        std::cout << e.what() << '\n';
    }
}

Possible output:

bad function call

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
LWG 2233	C++11	what() always returned the same explanatory string as std::exception::what()	returns its own explanatory string

See also

function (C++11)

copyable wrapper of any copy constructible callable object (class template)