Crash on non-supported input image

[jtippet]

If a non-supported file format is passed to Image::Hash->new, then the module crashes (around line 105 on v0.03, if using GD backend). The test against $self->{'im'} == 0 is incorrect, as that's not how an undef result gets stored.

I patched it on my copy with this:

my $img = GD::Image->new($self->{'image'});
if (not defined $img) {
    . . . return undef;
}

That fixes the crash.

Sidenote 1: But actually there's still a massive memory leak. If you pass multiple non-image files, you watch perl's RAM usage skyrocket and eventually get OOM-killed. Apparently the image buffer isn't cleaned up in that error path. I imagine that's a bug in libgd (v 2.1.0-3) or its Perl binding (v 2.50).

Sidenote 2: I encountered this problem because my corpus of ".jpg" files contains some files that are actually Windows BMP files with a .jpg extension. Apparently mis-labeling files is fairly common. GD doesn't support Windows BMP files, so it rejects those inputs. It would be helpful if Image::Hash automatically detected this sort of problem, and fell back to ImageMagik or some other backend.

[runarbu]

You are absolutely right, == 0 is of course not the correct way to test for undef. Strangely however so dos it kind of work on my pc with Perl 5.16. I do get an error (Use of uninitialized value in numeric eq (==) at lib/Image/Hash.pm line 105.) but the expression still gets evaluated to true and don’t crash the program at that line.

However I have changed it like you suggested.

Sidenote 1

This sounds like a bug in libgd. It is hard to make memory leaks in Perl, and the module will go out of scope when it crashes, so Perl should be able to free the memory Perl allocated. However it is quite different in the C and malloc() world where libgd lives.

Sidenote 2

GD only supports GIFs, JPEGs, PNGs, and WBMPs (WBMPs=Wireless Application Protocol Bitmap Format, not Windows Bitmap). I agree that a test for this and a fell back to Image::Magick would be nice.

I will look into adding it as a new function at a future date.