Date: Fri, 26 Apr 1996 12:59:45 -0700 (PDT)
From: Jag <gaghon AT nevada DOT edu>
To: Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
cc: djgpp AT delorie DOT com
Subject: Re: problem with DJGPP and arrays.
In-Reply-To: <Pine.SUN.3.91.960426111810.26200G-100000@is>
Message-ID: <Pine.OSF.3.91.960426123526.29873B@pioneer.nevada.edu>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII



On Fri, 26 Apr 1996, Eli Zaretskii wrote:

> 
> On Thu, 25 Apr 1996, Jag wrote:
> 
> > They are static variables, declared outside function.  I tried enlarging 
> > the stack to 2megs and it still did the same thing.
> 
> Then the stack is not related to your problem.  Please post the minimum 
> code fragment that is required to see what you are doing, and the exact 
> error message that is printed when the program crashes.  Did you check 
> that you don't read more data than the length of the arrays?
> 

Here is the funny part.  If I create an extra array BEFORE the array I 
get the error from, then it works.  I checked the size several times, but 
it does not explain why the same size array works with the extra array, 
but not without it.  I don't use the extra array.  I just put it there as 
padding.


Here is the error message:

Page fault at eip=00009985, error=0006
eax=00000000 ebx=00004000 ecx=00001000 edx=00000000 esi=00015280 edi=00000000
ebp=002297a4 esp=00229794 cs=00a7 ds=00bf es=00af fs=008f gs=00bf ss=00af
Call frame traceback EIPs:
  0x00009985   ___dj_movedata+33
  0x00007f3e   ___dosmemget+30
  0x00005bf5   __read+197
  0x00004b66   _fread_t2+54, line 6137 of towers2.c
  0x00002308   _main+584, line 177 of towers2.c
  0x000054ab   ___crt1_startup+115

-----------------------------------------------------


The same thing happens if I use fread/fopen instead of _read/_open.

-----------------
...  /* other arrays before (appx 1 meg )*/
int map[8130], table[5310], table2[1440];
...  /* other arrays after (appx 1meg) */

...
fread_t2( &map[0], "map.dat", 32500);
fread_t2( &table[0], "table.dat", 21200);<- error occurs here (line 177)  
fread_t2( &table2[0], "table2.dat", 5716);
-----------------

...  /* other arrays before (appx 1 meg )*/
int map[8130], table[5310], table2[1440];
...  /* other arrays after (appx 1meg) */

...
fread_t2( &map[0], "map.dat", 32500);
/* fread_t2( &table[0], "table.dat", 21200);  */
fread_t2( &table2[0], "table2.dat", 5716);

If I remark the fread_t2() then it works. No other fread()s fail.

------------------------

...  /* other arrays before (appx 1 meg )*/
int map[8130], dummy_table[5310], table[5310], table2[1440];
...  /* other arrays after (appx 1meg) */

...
fread_t2( &map[0], "map.dat", 32500);
fread_t2( &table[0], "table.dat", 21200); 
fread_t2( &table2[0], "table2.dat", 5716);

If I add a dummy array, then all the fread()s work.

-----------------------------------


Thanks for your help,

Vince