GNU bug report logs - #18857
floating point exception on invalid argument

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From: Tobias Stoeckmann <tobias <at> stoeckmann.org>
To: 18857 <at> debbugs.gnu.org
Subject: bug#18857: floating point exception on invalid argument
Date: Mon, 27 Oct 2014 21:06:01 +0100

Hi,

on 64 bit systems, an invalid tabsize argument can trigger a floating
point exception:

$ diff --tabsize=9223372036854775808 . .
Floating point exception

Offending line is this one:
    intmax_t off = (w + t + GUTTER_WIDTH_MINIMUM) / (2 * t)  *  t;

The tabsize I supplied is 2^63, multiplying by 2 will be 2^64 which
is too large, so the divisor overflows to 0.

This is a purely cosmetical fix, I don't see the need to adjust anything
except avoiding this special value.  I doubt that anyone ever needed
these large numbers.


Tobias

--- diffutils-3.3/src/diff.c~	2014-10-27 20:54:30.968656876 +0100
+++ diffutils-3.3/src/diff.c	2014-10-27 20:54:41.360708407 +0100
@@ -594,7 +594,7 @@
 
 	case TABSIZE_OPTION:
 	  numval = strtoumax (optarg, &numend, 10);
-	  if (! (0 < numval && numval <= SIZE_MAX) || *numend)
+	  if (! (0 < numval && numval <= SIZE_MAX / 2) || *numend)
 	    try_help ("invalid tabsize '%s'", optarg);
 	  if (tabsize != numval)
 	    {

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