Message-ID: <20021213021036.8008.qmail@web13003.mail.yahoo.com>
Date: Thu, 12 Dec 2002 18:10:36 -0800 (PST)
From: Thomas Tutone <thomas8675309 AT yahoo DOT com>
Subject: Re: simple inequality evaluation fails?!?!
To: djgpp AT delorie DOT com
Cc: hotcakes AT planetquake DOT com
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Reply-To: djgpp AT delorie DOT com


"Edd Dawson" <hotcakes AT planetquake DOT com> wrote in
message
news:<c5aK9.1738$2E DOT 528 AT news-binary DOT blueyonder DOT co DOT uk>...
> Hi,
> 
> I came across an unexpected result when executing a 
> program I'm 
> writing. After tracking it down in the source, I 
> wrote a few lines of 
> test code and found that a simple evaluation of an 
> inequality was 
> failing. Here is the small chunk of test code from 
> the program I am 
> writing:
> 
> //test code starts here
> 
> printf("\nRPP = %d\n", raysperpixel);
> if(raysperpixel < 1)
>      printf("%d is less than 1\n", raysperpixel);
> else
>      printf("%d is greater than or equal to 1\n", 
> raysperpixel);
> 
> //test code ends here
> 
> raysperpixel is an int (i.e its defined properly).
> Here is the corresponding output:
> 
> RPP = -35
> -35 is greater than or equal to 1
> 
> This makes about as much sense as the program's
output! Can anyone 
> help me out? I'm pretty sure it's a bug, but I 
> wanted to check here 
> before making a bug report. I'd be happy to submit >
the source of my 
> program if anyone wants to help me further!  = )
> If it matters at all, the value of 'raysperpixel' 
> was obtained from a string
> using the strtol function from the standard library 
> i.e I used the line:
> raysperpixel = (int)strtol(keyvalues[8], NULL, 10);
> 
> Any help with this would be great, even if it's 
> only to confirm that 
> it's a bug!
> 
> Edd
> 

I think the bug is in your program.  I just typed in
the the following program:

#include <stdio.h>

int main()
{
  int raysperpixel;
  raysperpixel = -35;
  printf("\nRPP = %d\n", raysperpixel);
  if(raysperpixel < 1)
    printf("%d is less than 1\n", raysperpixel);
  else
    printf("%d is greater than or equal to 1\n",
            raysperpixel);
  return 0;
}

I successfully compiled it as follows:

gcc -o test.exe test.c -W -Wall -pedantic

When I executed it, I got the following output:

RPP = -35
-35 is less than 1

In other words, I can't duplicate your error.  My
guess is you've mistakenly defined raysperpixel as an
unsigned int instead of an int, which would cause the
error you describe.

Please do the following:  Cut and paste (don't
retype!) the above example program and compile and
execute it on your system and see if you get the
correct result.  Assuming you do, please provide a
brief example - as brief as mine, please - that we can
actually compile all by itself and that generates your
error.  Your test code is not a stand-alone program,
so we have no way of testing it, and as I said, when I
drop your code into the program above, it works fine.

Hope that helps.

Best regards,

Tom


__________________________________________________
Do you Yahoo!?
Yahoo! News - Today's headlines
http://news.yahoo.com