Do local variables use heap for storage?

In addition to CcoollzZ's answer, you can refer to this[^] for a detailed explanation on the subject.
Also have a look at this[^] thread. :)

The stack is used when you do not use new or malloc or other related memory allocation functions explicitly.

For example:

int x;//<--- stack space is used.

int *x = new int();//<--- heap space is used. 

Relating to function calls, the function call, and the parameters passed in, and the variables declared inside the function are all on the stack unless you explicitly allocate them on the heap.

void myFunc(int x)
{
  int y;//<--- allocated on the stack
}

Anything allocated on the heap must be freed. For C allocations use free, for C++ allocations use delete or delete[] for arrays.

You can also find my answer here which gives a lot more differences between the stack and the heap.

With all the compilers I've used the heap isn't used for holding local variables, either when they're defined or passed to functions.

HOWEVER there's no reason why a compiler internally couldn't generate code to do this if it didn't change the observable behaviour of the program.

And don't be fooled that because something is declared as a local variable it automatically ends up on the stack. Compiler optimisers are quite good at sticking stuff in registers and other tricks that make it difficult to determine what's going where.

Basically don't assume anything about where a variable is stored and you'll be okay. Unless you're writing something like a garbage collector in which case you have to care but that's not something ordinary mortals like me would consider doing.

Cheers,

Ash