_expand() and _msize()
 

In windows I could use _expand() to take a piece of memory and enlarge it and _msize() to determine what the memory size in bytes (which I got from malloc.h, I think) is but in Linux I got compiling errors with those 2 functions.

I just want to know if there are Linux equivalent functions for C++ ?

In general you should be using new and delete in C++ to allocate memory.

However... if your interested... the following C functions exist under Linux.

malloc - allocates memory
realloc - reallocates a memory block (allows you to change the size).
malloc_size - reports the size of a block you have allocated

EDIT: btw... they are all availible in stdlib.h.