std::bad_function_call

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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.

cpp/error/exception std-bad function call-inheritance.svg

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

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 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

[virtual]
 destroys the exception object
(virtual public member function of std::exception)
[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

(C++11)
 copyable wrapper of any copy constructible callable object
(class template)
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