Bug #5282 for GDGraph: [PATCH] Infinite loop in GD::Graph::axestype::_best_ends

Distribution: GDGraph 1.43 File: axestype.pm (revision 1.44) Description: When the min and max values for the y-axis are both negative, halving the minimum and increasing the maximum by 50% results in a minimum greater than the maximum, giving a negative range. This leads to an infinite loop in the sub _best_ends at the following line: 1651 while ($s > $range) { $s /= 10 } as $s is never going to become negative, just closer and closer to zero. The patch below resolves this issue. --- axestype.pm.orig 2003-12-09 17:06:53.000000000 +1100 +++ axestype.pm 2004-02-11 15:42:07.000000000 +1100 @@ -1622,15 +1622,15 @@ my ($best_min, $best_max, $best_num) = ($min, $max, 1); + # Check that min and max are not the same, and not 0 + ($min, $max) = ($min != 0) ? ($min * 0.5, $min * 1.5) : (-1,1) + if ($max == $min); + # mgjv - Sometimes, for odd values, and only one data set, this will be # necessary _after_ the previous step, not before. Data sets of one # long with negative values were causing infinite loops later on. ($min, $max) = ($max, $min) if ($min > $max); - # Check that min and max are not the same, and not 0 - ($min, $max) = ($min != 0) ? ($min * 0.5, $min * 1.5) : (-1,1) - if ($max == $min); - my @n = ref($n_ref) ? @$n_ref : $n_ref; if (@n <= 0)

To reproduce: #!/usr/bin/perl -w use GD::Graph::lines; my $g = GD::Graph::lines->new(1200, 300); my $data = [ [ '1', '2', '3', '4'], [ -1, -1, -1, -1 ] ]; print $g->plot($data)->png; The following code in axestype.pm (sub _best_ends) seems to bear the blame: ... # mgjv - Sometimes, for odd values, and only one data set, this will be # necessary _after_ the previous step, not before. Data sets of one # long with negative values were causing infinite loops later on. ($min, $max) = ($max, $min) if ($min > $max); # Check that min and max are not the same, and not 0 ($min, $max) = ($min) ? ($min * 0.5, $min * 1.5) : (-1,1) if ($max == $min); ... This fails when $min==$max and they are negative, because later on ... my $range = $max - $min; # create array of interval sizes my $s = 1; while ($s < $range) { $s *= 10 } while ($s > $range) { $s /= 10 } #### <<<< we are stuck here ... My fix for this is to do the artificial range widening first, and then swap if necessary: ... # Do this first if we have a constant graph ($min, $max) = ($min) ? ($min * 0.5, $min * 1.5) : (-1,1) if ($max == $min); # Swap if we ended up with inverted (min, max) ($min, $max) = ($max, $min) if ($min > $max); ...