Bug#1118385: Non-reproducibility in pdfTeX

On 5/16/26 2:55 PM, Norbert Preining wrote:
>> I rebuilt the Debian libpng package with the patch in place and installed it
>> into my test chroot, the pdftex binary is linked with the lib in that
>> package. The consequential pdflatex runs still generate pdf files with
>> different check sums.
> 
> Hmm. Interesting. I just rebuild from the texlive sources which
> incorporate this change.
> 
> After that, the test Akira gave showed no differences
> 
> Test was:
> TeX file loading the valuators.png, run it at least 2 secs apart, make
> sure that the PDF ids are the same.
> After that, I get bit-identical PDFs (this is with pdftex binary against
> patched libpng in texlive sources):
> 
> $ cat valuators.tex
> \documentclass{article}
> \usepackage{graphicx}
> \begin{document}
> Hello.
> 
> \includegraphics[width=8cm]{valuators.png}
> \end{document}
> 
> $ md5sum valuators.png
> bad89b034cc9466d65ee95451e81a58c  valuators.png
> 
> $ for i in 1 2; do pdflatex -interaction=batchmode "\pdfinfo{/CreationDate(D:20260429034606Z)/ModDate(D:20260429034606Z)}\input{valuators.tex}"; mv valuators.pdf valuators${i}.pdf; sleep 2; done
> .....
> 
> $ cmp valuators1.pdf valuators2.pdf
> 
> $ echo $?
> 0

Did you also set SOURCE_DATE_EPOCH, e.g.,like Akira did:

   export SOURCE_DATE_EPOCH=`perl -e "print time();"`
   export FORCE_SOURCE_DATE=1

Best regards,
John