Heap Memory in C Programming

Question

What exactly is heap memory?

Whenever a call to malloc is made, memory is assigned from something called as heap. Where exactly is heap. I know that a program in mai

Answer 1

Reading through this, this is actually beyond the realms of C. C doesn't specify that there's a heap behind malloc; it could just as easily be called a linked list; you're just calling it a heap by convention.

What the standard guarantees is that malloc will either return a pointer to an object that has dynamic storage duration, and your heap is just one type of data structure which facilitates the provision of such a storage duration. It's the common choice. Nonetheless, the very developers who wrote your heap have recognised that it might not be a heap, and so you'll see no reference of the term heap in the POSIX malloc manual for example.

Other things that are beyond the realms of standard C include such details of the machine code binary which is no longer C source code following compilation. The layout details, though typical, are all implementation-specific as opposed to C-specific.

The heap, or whichever book-keeping data structure is used to account for allocations, is generated during runtime; as malloc is called, new entries are (presumably) added to it and as free is called, new entries are (again, presumably) removed from it.

As a result, there's generally no need to have a section in the machine code binary for objects allocated using malloc, however there are cases where applications are shipped standalone baked into microprocessors, and in some of these cases you might find that flash or otherwise non-volatile memory might be reserved for that use.