Date: Tue, 22 Apr 2003 08:45:35 -0500
From: Eric Rudd <rudd AT cyberoptics DOT com>
Subject: Re: Bug 00314 -- div() still broken
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Ben Peddell wrote:

> From your crash, it looks like the divide was being called something 
> like:
> result = div(-3,-3); 

Those args shouldn't even cause it to bomb.  I think I had some problem 
with -fomit-frame-pointer, but I'm still investigating.

> And the results:
>
> Linux div(40,-3) = -13, 1
> Asm   div(40,-3) = -13, 1
> C     div(40,-3) = -13, 1
> DJGPP div(40,-3) = -13, -1 

According to C99:

   6.5.5  Multiplicative operators

   [#6] When integers are divided, the result of the / operator
   is  the  algebraic  quotient  with   any   fractional   part
   discarded.78)   If  the  quotient  a/b is representable, the
   expression (a/b)*b + a%b shall equal a.

...so the 2.03 DJGPP div() is incorrect, since (-13)*(-3) + (-1) != 40.  
I knew this when I submitted 00314, but the log for 00314 claims that 
the bug was fixed in 2000.

> I think you can see the odd one out.
>
> By the way, the libc reference in DJGPP says that the DJGPP result is 
> correct.

OK, so we have a bug in the docs as well.

-Eric Rudd
rudd AT cyberoptics DOT com