From:	"Andrew Davidson" <andrew AT lemure DOT freeserve DOT co DOT uk>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: How does DJGPP store its structs?
Date:	Wed, 31 Mar 1999 23:51:04 +0100
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Marp <Marp AT 0 DOT 0 DOT 0 DOT 0> wrote in message
news:7dss2u$ke1 AT dfw-ixnews11 DOT ix DOT netcom DOT com...
> Andrew Davidson <andrew AT lemure DOT freeserve DOT co DOT uk> wrote in message
> news:7dse20$rp8$1 AT news7 DOT svr DOT pol DOT co DOT uk...
> >
> > mainstruct *mystruct;
> > unsigned long *test;
> >
> > test=(unsigned long *)malloc(4);
> > // this will crash it with a sigsegv
> > mystruct->doublepair1->dp=test;
>
> Did you get a warning about uninitialized variables when you compiled????
> You forgot to initalize mystruct and doublepair1. You can't assume DJGPP
(or
> any other compiler) will do that for you. You must do that first to access
> members. Try this:
>
> mainstruct *mystruct;
> unsigned long *test;
>
> test=(unsigned long *)malloc(4);
>  /* adding these two lines will stop it from crashing */
> mystruct = (mainstruct *)malloc(sizeof(mainstruct));
> mystruct -> doublepair1 = (dpair *)malloc(sizeof(dpair));
>
> mystruct->doublepair1->dp=test;

Okay... but that far I (eventually) managed to work out for myself. Now what
if I want to do:

mystruct->doublepair1->p->ph->b->l=test;

Anything accessing any structures below dp seems to crash. I've tried
mallocing memory for all these pointers but no joy... I can only assume I'm
not mallocing the right stuff. Any hints?

Andrew

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