Heap Pointer

[John Gonzaga]

What's the best way to get the heap pointer? I tried using _sbrk(0) and 
I get an undeclared error, I've already included unistd.h. I'm 
currently using:

gcc 3.3.2
newlib 1.10.0
binutils 2.11.2
target is ARM, little endian.

Thanks.

-John G-