[poppler] Cannot open in poppler 0.22.1 a file saved after large file support patches

Fabio D'Urso fabiodurso at hotmail.it
Thu Apr 25 13:57:17 PDT 2013

On Saturday, February 16, 2013 10:57:36 AM Adrian Johnson wrote:
> On 16/02/13 09:53, Fabio D'Urso wrote:
> > Hi,
> > 
> > I'm not able to open files saved by git-master poppler in poppler 0.22:
> > Syntax Error: Couldn't find trailer dictionary
> > Syntax Error: Couldn't read xref table
> > 
> > I noticed that large file support patches changed how we write incremental
> > updates of XRef streams. In particular I'm referring to
> > XRef::XRefStreamWriter::writeEntry and XRef::writeStreamToBuffer.
> > 
> > Previously we used to write 4-bytes offsets in XRef streams, now we always
> > write 8-bytes offsets (sizeof(Goffset)).
> > If I understand correctly older poppler versions are not able to read
> > those files because they don't have large file support.
> > 
> > In other words, even if the files we create are good, all previous poppler
> > versions (including 0.22.1) are not able to open them back.
> Could you open a bug to track this issue.

Sorry, I haven't opened a bug. But I've written patches :)

> > Maybe we had better keep emitting 4-bytes entries for compatibility when
> > possible (i.e. if no offset exceeds the 4GB limit), what do you think?
> Yes it would be best to check if all offsets in the xref stream are less
> than 4GB and if so, write 4 byte offsets.

This is done in the first attached patch.

I've also attached two other patches that fix a printf format specifier (%i 
should now be %lli because it refers to a Goffset).
The second patch adds the printf-format attribute to OutStream::printf, so the 
compiler can spot this kind of errors. The third one is the actual fix.
This fixes the startxref value being sometimes negative on little-endian cpus 
where int is 32-bit, and zero on big-endian cpus where int is 32-bit.

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