Date: Tue, 15 Jul 1997 12:31:38 -0700 (PDT)
Message-Id: <199707151931.MAA08025@adit.ap.net>
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To: kwe1 AT flash DOT net
From: Nate Eldredge <eldredge AT ap DOT net>
Subject: Re: HELP! DJGPP Program Crashes
Cc: djgpp AT delorie DOT com
Precedence: bulk

>I'd like to what causes the abnormal crashes in my programs... Whenever I
>seem to use a certain function too much it bombs to DOS (see below). I know
>where the problem is, I just don't know why it occurs... 

Some more details would be nice. What sort of error message does it get? Try
using `symify' on the traceback and posting it here.
>What are the
>limits, if any, imposed on DJGPP code, other than normal errors (my progs
>compile fine, they just don't run fine...)?
DJGPP runs your programs in protected mode. This means that:
- They are not normally allowed to touch memory outside their area.
  The exceptions to this are the farptr functions and nearptr_enable.
- Dereferences of null or invalid pointers are caught and result in an error
message with traceback.
Also:
- The stack is, by default, 256K in size. This can be changed with `stubedit'.

> When I deal with a certain
>pointer too much it does the same (for some reason, it only will be dealt
>with three times in the main () function... you can declare it, but if you
>touch it.....)
Are you sure your pointer is valid?
>And BTW, does DJGPP have
>options for changing memory models, or does it all compile into medium?
I'm not sure what you mean. DJGPP programs are 32-bit and run with a flat
memory model- all data selectors (ds, es, ss) are the same.
>
>void setpal(int num, byte red, byte gre, byte blu)
>{
>   outportb(0x3C8, num);
>   outportb(0x3C9, red);
>   outportb(0x3C9, gre);
>   outportb(0x3C9, blu);
>}
I see no problem with your function, assuming `byte' is typedef'ed to
`unsigned char'. How deeply is it nested when you call it?

It looks to me like you're used to a real-mode compiler. DJGPP may take a
bit of getting used to in this case.

Nate Eldredge
eldredge AT ap DOT net