From: Thomas Demmer <demmer AT LSTM DOT Ruhr-UNI-Bochum DOT De>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Bug report: Structs
Date: Tue, 28 Jan 1997 08:40:42 +0100
Organization: Lehrstuhl fuer Stroemungsmechanik
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Message-ID: <32EDAD7A.794B@LSTM.Ruhr-UNI-Bochum.De>
References: <199701220247 DOT UAA37718 AT audumla DOT students DOT wisc DOT edu>
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CC: kkunen AT facstaff DOT wisc DOT edu
To: djgpp AT delorie DOT com
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Adam Kunen wrote:
> 
>         I think this is the right address for bug reports on DOS port of GNU
> C... But anyway, I was using GNU C and found that when you have a structure
> bigger than 64k it tends to crash.  Although I havn't spent time to pinpoint
> exactly what is causing the problem, I beleive that it crashes when you make
> a function call with a large structure as an argument.  I assume that doing
> this is okay because gcc doesn't report any warnings or errors, so I've come
> to the conclusion: It's a bug!
>         I hope this helps,
>                         Adam Kunen,
>                         kkunen AT facstaff DOT wisc DOT edu
> 
> PS: I was told to give an example code file to illustrate the problem:
> 
> struct FooType {
>         char blah[1024][128];
> };
> 
> void foobar(struct FooType ptr){
>         return;
> }
> 
> int main(void){
>         struct FooType eek;
>         foobar(eek);
>         return 0;
> }
> 
> Adam "El grande queso" Kunen
> kkunen AT facstaff DOT wisc DOT edu
This is not a bug, but rather a misfeature.
You are doing two things that make the program 
crash: 
You have a local 1 MB structure in main on
the stack, and you push a copy of that structure
on the stack. Thus, you'd need 2 Meg of stack space.
Run stubedit on the executable and find that the
default stack is 512 k, or so. I'm not
sure if you can increase this to 2 Meg and a
bit more, but it is for sure better to say

 void foobar(struct FooType *ptr){
         return;
 }
 int main(void){
         struct FooType *eek;
	 eek =  malloc(sizeof FooType);
         foobar(eek);
         return 0;
 }
( Syntax unchecked )

You just move 4 bytes around when calling foobar() instead of
2 Megs.

-- 
Ciao
Tom

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* Thomas Demmer                                             *
* Lehrstuhl fuer Stroemungsmechanik                         *
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