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Stack size question

Posted on 1998-05-20
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Last Modified: 2010-04-10
I get a stack overflow error at run time...

How do i increase the stack size in Borland's Turbo C++ 4.5?

Jeff
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Question by:jkelly061597
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by:nietod
ID: 1164418
If this is a windows program the stack size specified is the initial stack size, the stack will grow as needed so you shouldn't run into a stack overflow unless you have a bug.  (Or iif you know that you legitimately use a LOT of stack space.)  So if this is a windows program that doesn't have unusual stack usage, look for a bug, like infinite recursion instead of changing the stack space.  If this is a DOS program, you might be running out of stack space, so ignore this.
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Expert Comment

by:chensu
ID: 1164419
I guess it is a DOS program. Do you use any large array allocated on the stack like the following? Use dynamic allocation instead (C++ operator new and delete) or simply define it as a static or global variable allocated on the heap.

void MyFunc()
{
    ...
    char achBuf[2048];
    ...
}

Another possible reason causing this is a deep recursive function.
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Author Comment

by:jkelly061597
ID: 1164420
I have a large array of classes... would this fit the large array description?
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by:chensu
ID: 1164421
Yes.
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by:chensu
ID: 1164422
Just try putting "static" there to see whether the error still exists. If not, this should be an answer. :-)


void MyFunc()
{
    ...
    static CMyClass myObjects[2048];
    ...
}

I would suggest using dynamic allocation instead of using static or global variables. Using static or global variables will make your executable files bigger.
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Expert Comment

by:RONSLOW
ID: 1164423
In DOS you are more limited in your address space .. there isn't any virtual memory, so when it is full, it is full.
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Expert Comment

by:nietod
ID: 1164424
However, in DOS you can set the stack size.  And this is the maximum stack size, since the stack does no grow, so it is important.  However, you are limited to a pretty small stack so your best bet is probably to reduce your stack usage as Chensu suggested (since it seems like you are unneccesarily using stack space).  

I would tell you how to set stack size, just so you know, but I'm using VC 5.0 which doesn't produce DOS programs, so I don't know.
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Author Comment

by:jkelly061597
ID: 1164425
How do I dynamically allocate my array?
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Accepted Solution

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nietod earned 50 total points
ID: 1164426
for an array 100 objects of class "Cls" you would do

Cls *ClsAry = new Cls[100];

Note that the 100 does not have to be "hardcoded"  it could be a variable.  This allows you to allocate arrays of whatever size you determine you need at run-time.

Are you familar with using "new" and "delete"?
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Expert Comment

by:RONSLOW
ID: 1164427
to dynamically alocate you create an array of POINTERS to your class objects (allocate with new or malloc or stl classes or whatever) and then for each entry, use new to allocate the objects and store pointers to the in the array.  You need to be careful when doing things like removing elements or copying them.  If not, you can end up with dangling pointers or inaccessible objects.

Techniques like smart pointers can help you manage your objects without you needing to anything (much) special in your code.


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Expert Comment

by:nietod
ID: 1164428
Roger, is that just for jkelly's additional edification.  Or is there some evidence that I missed that he wants an arrray of pointers.
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by:RONSLOW
ID: 1164429
if he wants to take advantage of dynamic storage to avoid using up stack space, then creating the class objects on the heap and storing pointers only in the array should help.

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Expert Comment

by:RONSLOW
ID: 1164430
Alternatively, there are dynamic array classes in the standard stl library that could do the trick.  Does Turbo C++ 4.5 have STL support?

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Expert Comment

by:chensu
ID: 1164431
I am sure Turbo C++ 4.5 does not support C++ template.
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Expert Comment

by:chensu
ID: 1164432
jkelly,

Have you tried what I suggested?
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Expert Comment

by:RONSLOW
ID: 1164433
In that case, without STL (and templates) if Jeff wants to make use of dynamic allocation, he would be better allocating the objects with new and storing pointers to them in a dynamic array (can you malloc/realloc/free to do the dynamic array).

He should probably wrap this dynamic array in a class so that he can control the allocation, freeing, copying etc of the array and its elements.


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Author Comment

by:jkelly061597
ID: 1164434
When I created a static array rather than automatic I was able to avoid the overflow...

I'm trying to tweek the code withyour given info...

---

Is this the proper use of delete:

delete my_array;
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Expert Comment

by:nietod
ID: 1164435
Yes, but only in my_array was allocated with new, like

int *my_array = new int;

If my_array was allocated with new [], then use delete [], like

int *my_arrray = new int[10];
delete [] my_array;

If my_array is not dynamically allocated, that is, it is global, local, or static don't use delete or delete[]!
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