How is heap and stack memories managed, implemented, allocated?

Question

In C/C++ we can store variables, functions, member functions, instances of a class either on a stack or a heap.

How is each implemented? How is it managed (high lev

Answer 1

Basically the heap is not implemented by the compiler, but instead by the C runtime library. Obviously this code is very platform dependent. On Unix or Unix-like systems the implementation is generally based on the sbrk/brk system call and a bigger amount of memory is allocated to reduce the number of system calls. This memory is then managed by the heap memory manager. If more memory is required a new call to sbrk is is issued. The current end address of the heap can be obtained with sbrk(0) if you are interested in debugging the heap management routines. Most memory managers to do not return memory to the OS during the lifetime of a process (gnu c runtime library does if certain constraints are met).

A more detailed description is available in http://gee.cs.oswego.edu/dl/html/malloc.html.