[bug-diffutils] bug#18857: floating point exception on invalid argument

[Tobias Stoeckmann]

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)
            {