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Heap Allocators in C++

What Are Heap Allocators?

Heap allocators allocate memory blocks to programs as needed. This means that when a program needs more memory than available, the heap allocator will find some free space and return it to the program.

Why Do We Need Them?

Most programming languages use one of two different approaches to managing memory. One approach is called “stack based” because it uses a stack to manage memory allocations. The other approach is called “heap based.” Heap allocators work with the heap, which is a large pool of memory managed by the operating system.

The Three Types of Heap Allocators

There are three main types of heap allocators: manual, automatic, and hybrid. Manual heap allocators require programmers to manually allocate and deallocate memory. Automatic heap allocators do not require any programmer intervention. Hybrid heap allocators combine elements of both manual and automatic heap allocators.

Implementing a Custom Heap Allocator

To implement a custom heap allocator, you must first understand how the standard library’s default heap allocator works. This will help you decide whether you need to write your own heap allocator. If you do, then you should read up on the details of the standard library’s default allocator so you can make informed decisions when writing your own.


As you’ve seen, there are several ways to allocate memory in C++. You can use new, malloc, calloc, realloc, and free. Each has its advantages and disadvantages.