Segmentation fault when replacing a tag by itself

[Yannick Patois]

Hi,

I first used the version 0.1.3 provided by my distribution (Ubuntu Lucid on i386), and used the following code (extract):

d1=pyexiv2.Image("org/img_9085.jpg")
d2=pyexiv2.Image("ok/img_9085.jpg")
d1.readMetadata()
d2.readMetadata()
for key in d1.exifKeys():
  print str(key)+" : "+str(d1[key])
  d2[key]=d1[key]

This crashed on "Exif.CanonCs.Lens : (55, 18, 1) ValueError: invalid literal for int() with base 10: '(55, 18, 1)" which is a known bug, that has been fixed in most recent versions.

So I installed first the 0.2.2 and the the latest brz one with the same outcome.

The code is now:

d1=pyexiv2.ImageMetadata("org/img_9085.jpg")
d2=pyexiv2.ImageMetadata("ok/img_9085.jpg")
d1.read()
d2.read()
for key in d1.exif_keys:
  print str(key)+" : "+str(d1[key])
  d2[key]=d1[key]

And it crash just after the d2[key]=d1[key] affectation printing only:

Exif.Image.Make : <Exif.Image.Make [Ascii] = Canon>
Segmentation fault

I used the version 0.19-1 of libexiv2 (the one distributed by ubuntu).

Thanks for any help.

[Yannick Patois (patois)]

Simplification of the problem:

This is enough to crash:
d1=pyexiv2.ImageMetadata("org/img_9085.jpg")
d1.read()
for key in d1.exif_keys:
  print str(key)+" : "+str(d1[key])
  d1[key]= d1[key]

That works until a non string is required ( Invalid value for EXIF type [Short]):
d1=pyexiv2.ImageMetadata("org/img_9085.jpg")
d1.read()
for key in d1.exif_keys:
  print str(key)+" : "+str(d1[key])
  d1[key]= str(d1[key])

Sorry for first report and I agree that it's still not very clear.

Can you reproduce?

Thanks.

[Olivier Tilloy (osomon)]

Thanks for the report Yannick. Could you please attach a sample picture with which the issue can be reproduced?

In the simplified case you’re describing in comment #1, do you still get a segmentation fault, or is it a python exception that aborts "cleanly" the execution of your script?

[Yannick Patois (patois)]

Thanks for your prompt answer.

Yes, the first crash is an hard crash. I gdb it, but couldnt go very far. It crash in
const ExifTag Image::getExifTag(std::string key)
at this call: _exifData->findKey(exifKey);

I attached the code and a sample image.

Thanks.

Yannick

[Olivier Tilloy (osomon)]

I can reproduce with the unit test provided and any image containing EXIF metadata.

[Olivier Tilloy (osomon)]

Here is the relevant part of the backtrace obtained with gdb:

#0 0x0000006e in ?? ()
#1 0x005e007b in Exiv2::ExifData::findKey(Exiv2::ExifKey const&) () from /usr/lib/libexiv2.so.6
#2 0x005e03e5 in Exiv2::ExifData::operator[](std::string const&) () from /usr/lib/libexiv2.so.6
#3 0x004efaf3 in exiv2wrapper::ExifTag::setParentImage(exiv2wrapper::Image&) () from /home/osomon/dev/pyexiv2-branches/pyexiv2/build/libexiv2python.so

The problem is with re-setting the parent image of a tag (not just EXIF tags for that matter, the same issue likely exists for IPTC and XMP tags) to the same owner image. It should be relatively easy to add a check to avoid the problem.

@Yannick: note that the bug can easily be worked around by doing something like this:

    d1[key] = pyexiv2.ExifTag(key, d1[key].value)

or, even more concise:

    d1[key] = d1[key].value

[Olivier Tilloy (osomon)]

Lowering importance as an easy-to-implement workaround has been identified.

[Olivier Tilloy (osomon)]

I’m working on a branch that adds unit tests for this case and fixes the issue for EXIF and IPTC tags. A bit more work is required for XMP.

[Yannick Patois (patois)]

Thanks you very much for your prompt reaction and the quick fix (adding .value). It works fine for me now.

[Olivier Tilloy (osomon)]

Fixed in the trunk with revision 321.