Issue with attachfile2: Non-PNG Files Truncated in Output PDF

[Albschu]

Hi everyone,

I'm using Tectonic and attachfile2 to embed files into a PDF. While PNG files attach and extract correctly, other formats like .html, .txt, or .tex appear broken after extraction. The issue occurs even with very small files (e.g., a simple "Hello World" HTML file).

What Happens:

• The attachment process itself seems to work.
• The embedded file matches the original. However, after extracting from the compiled PDF, the content gets truncated at an arbitrary point.
• File size doesn't seem to be the issue.

What I Tried:

• Comparing the embedded and extracted files: identical until a cutoff point.
• Testing with different file types and sizes.
• Checking existing discussions, but only found issues related to attachment failures.

Does anyone know what could be causing this or how to work around it?

Thanks in advance!

[vlasakm]

Thanks for the description and diagnosis. I have seen this problem before: #935 (comment), but never dug deeper to find the problem.

I think I have now managed to track the problem down and have an idea for a fix: #1261.

@Albschu just for next time, it's often very useful to provide MWE with a bug report. In this case I believe compilation of your MWE would also show something like:

warning: 1024-byte read failed
caused by: failed to fill whole buffer

which points to the underlying problem.

Also please, feel free to start issues directly, no need for discussion if you see what appears to be a problem, and also especially if it works with XeLaTeX and not with Tectonic.

For future reference, this is the MWE I used:

\documentclass{article}
\usepackage{attachfile2}
\usepackage{filecontents}

\begin{filecontents*}{example.txt}
Example
\end{filecontents*}

\begin{document}

Attached file: \attachfile{example.txt}

\end{document}

Without patch in #1261 it shows the warning and the embedded file contents is empty, with the patch it correctly has the file contents.

I tested with:

cargo run --features external-harfbuzz -- test-1260.tex

And inspected the PDF file for the attached file:

mutool clean -dif test-1260.pdf test-1260.pdf
grep -a -B 2 -A 12 Embedded test-1260.pdf

Before patch:

After patch:

9 0 obj
<<
  /Type /EmbeddedFile
  /Params <<
    /Size 8
    /ModDate (D:20250222143457Z)
    /CheckSum <02FB126282CB0D596A9052BC21948326>
  >>
  /Length 0
>>
stream

endstream
endobj

After patch:

9 0 obj
<<
  /Type /EmbeddedFile
  /Params <<
    /Size 8
    /ModDate (D:20250222143609Z)
    /CheckSum <02FB126282CB0D596A9052BC21948326>
  >>
  /Length 8
>>
stream
Example

endstream
endobj