std::set_new_handler

 

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Low level memory management operator newoperator new[] operator deleteoperator delete[] nothrow_t nothrow new_handler set_new_handler get_new_handler (C++11) bad_alloc bad_array_new_length (C++11) align_val_t (C++17) destroying_delete_t (C++20) launder (C++17) Smart pointers unique_ptr (C++11) shared_ptr (C++11) weak_ptr (C++11) auto_ptr (until C++17*) owner_less (C++11) owner_less<void> (C++17) owner_hash (C++26) owner_equal (C++26) enable_shared_from_this (C++11) bad_weak_ptr (C++11) default_delete (C++11) out_ptr_t (C++23) inout_ptr_t (C++23) Miscellaneous pointer_traits (C++11) to_address (C++20) addressof (C++11) align (C++11) assume_aligned (C++20) is_sufficiently_aligned (C++26) C Library malloc calloc realloc free aligned_alloc (C++17)

 

Low level memory management

Functions

operator newoperator new[]

operator deleteoperator delete[]

get_new_handler (C++11)

set_new_handler

Classes

bad_alloc

bad_array_new_length (C++11)

align_val_t (C++17)

Types

new_handler

Objects

nothrow

destroying_delete (C++20)

Object access

launder (C++17)

 

Defined in header <new>
std::new_handler set_new_handler(std::new_handler new_p )throw();		(until C++11)
std::new_handler set_new_handler(std::new_handler new_p )noexcept;		(since C++11)

Makes new_p the new global new-handler function and returns the previously installed new-handler.

The new-handler function is the function called by allocation functions whenever a memory allocation attempt fails. Its intended purpose is one of three things:

1) make more memory available,

2) terminate the program (e.g. by calling std::terminate),

3) throw exception of type std::bad_alloc or derived from std::bad_alloc.

The default implementation throws std::bad_alloc. The user can install their own new-handler, which may offer behavior different than the default one.

If new-handler returns, the allocation function repeats the previously-failed allocation attempt and calls the new-handler again if the allocation fails again. To end the loop, new-handler may call std::set_new_handler(nullptr): if, after a failed allocation attempt, allocation function finds that std::get_new_handler returns a null pointer value, it will throw std::bad_alloc.

At program startup, new-handler is a null pointer.

This function is thread-safe. Every call to std::set_new_handlersynchronizes-with (see std::memory_order) the subsequent std::set_new_handler and std::get_new_handler calls.

(since C++11)

Parameters

new_p

-

pointer to function of type std::new_handler, or null pointer

Return value

The previously-installed new handler, or a null pointer value if none was installed.

Example

Run this code

#include <iostream>#include <new>   void handler(){std::cout<<"Memory allocation failed, terminating\n"; std::set_new_handler(nullptr);}   int main(){ std::set_new_handler(handler);try{while(true){ new int[1000'000'000ul]();}}catch(conststd::bad_alloc& e){std::cout<< e.what()<<'\n';}}

Possible output:

Memory allocation failed, terminating std::bad_alloc

See also

operator newoperator new[]	allocation functions (function)
get_new_handler (C++11)	obtains the current new handler (function)
new_handler	function pointer type of the new handler (typedef)
bad_alloc	exception thrown when memory allocation fails (class)