Having a program with a recursive function nested three times using
200 bytes of stack shouldn't by itself cause stack overflow. That's only
600-700 bytes of stack, and even with the 250 byte global, that's still less
than 1K. Are you sure you don't have a bug which results in excessive
levels of recursion?
As a general rule on this kind of platform with limited stack, you need
to minimize the use of stack, and recursive functions or heavily nested
non-recursive functions need be VERY stingy in their stack usage.
And a global array of 600 bytes will also allocate out of your stack
(I believe), but allocate it permanently as opposed to when the function is
being called. This should actually make things worse! (Can others confirm
or correct where globals are allocated?)
Best solution is to allocate the 200 bytes off the heap, which reduces your
stack usage per call by 196 bytes (or so). Also the 250 byte global should
be moved to the heap!
Additionally, you need to scan your code and ensure that other instances of
significant stack usage are moved to the heap whereever possible. It seems
like your program is almost out of stack, and you must be using it up
somewhere!
Particularily move instances of global arrays from the stack to the heap,
and any large arrays used in higher level functions.
Roger Stringer
Marietta Systems, Inc.
----------------------------------------------------------------------
>Understanding Dynamic Heap - Questions
>From: "Michael S. Davis" <[EMAIL PROTECTED]>
>Date: Mon, 7 Feb 2000 07:10:18 -0800 (PST)
>I am having a problem with stack overflow that is corrupting some
>global data and sometimes causes a Fatal Exception. I need some help
>understanding the dynamic heap and it's usage.
>I would like to read a detailed description of the stack and dynamic
>heap issues but the docs don't have enough information; or maybe I'm
>just dense:-)
>I have an application that uses a limited amount of recursion. I had
>placed limits on this and the current version of the app works
>fine. But I made a couple of changes and now I get the error. I made
>two changes:
> 1) I increased the size (approx 200 bytes) of a small array in one
> of the functions that is recursed. This is probably the source
> of my problem, if the local array uses dynamic heap, which I
> suspect does.
> 2) I added an additional global array that is approximately 250 bytes
> in size. This is the array that gets corrupted by problem in
> (1). So, these two are related some how.
>It is my understanding that the dynamic heap is limited to something
>like 12-14K. Is that true? Is this where global variables reside?
>It is also my understanding that the stack space is something like
>4K. Is that true? Do local variables in subroutines reside in the
>stack or the dynamic heap?
>If there is a stack overflow, does the stack just expand into the global
>variable space? Is there any way to test for this prior to it
>happening?
>Now, assume (1) is the source of my problem. The array is approx 200
>bytes in size. Now, if I recursively call this function 3 times that is
>approximately 600 (just for the array). Is that 600 bytes part of the
>stack or dynamic heap or what?
>If I created a global array that was 600 bytes and removed the 200 byte
>array from the function, would that relieve the problem or am I in the
>same fix?
>If instead of the global array, I used the memory manager to allocate
>600 bytes for the array, would that help?
>Is memory that is allocated by the MemManager part of the dynamic heap?
>Assuming that someone understands my problem, is there a way around this
>without having to eliminate the recursive calls?
>Is there any place where I can get a detailed description of the
>interaction of the stack with the dynamic heap and/or other memory.
>Thanks
>Mike
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