std::bad_alloc

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Defined in header <new>
class bad_alloc;

std::bad_alloc is the type of the object thrown as exceptions by the allocation functions to report failure to allocate storage.

cpp/error/exception std-bad alloc-inheritance.svg

Inheritance diagram

Member functions

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

std::bad_alloc::bad_alloc

(1)
bad_alloc() throw();
 (until C++11)
bad_alloc() noexcept;
 (since C++11)
(2)
bad_alloc( const bad_alloc& other ) throw ( ) ;
(until C++11)
bad_alloc( const bad_alloc& other ) noexcept;
(since C++11)

Constructs a new bad_alloc 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_alloc then std::strcmp (what( ), other.what ( ) ) == 0 (since C++11)

Parameters

other - another exception object to copy

std::bad_alloc::operator=

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

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

Parameters

other - another exception object to assign with

Return value

*this

std::bad_alloc::what

virtual const char * what( ) const throw ( ) ;
(until C++11)
virtual const char * what( ) const noexcept ;
(since C++11)
(constexpr since C++26)

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)

Notes

Feature-test macro Value Std Feature
__cpp_lib_constexpr_exceptions 202411L (C++26) constexpr for exception types

Example

Run this code
#include <iostream>
#include <new>
 
int main()
{
    try
    {
        while (true)
        {
            new int[100000000ul];
        }
    }
    catch (const std::bad_alloc& e)
    {
        std::cout << "Allocation failed: " << e.what() << '\n';
    }
}

Possible output: 

Allocation failed: std::bad_alloc

See also

 allocation functions
(function)
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