Tectonic seems to loop infinitely on this input file

[pkgw]

I have not yet sat down and tried to create a minimal test case. xelatex processes the file OK.

Also, apparently GitHub filters file extensions, so let's call this a .txt.

timeseries1.tex.txt

[ligfx]

I ran into the same issue with a Jupyter notebook exported to Latex, and minimized my file down to this:

\documentclass{article}

\usepackage{fancyvrb}
    
\makeatletter
\let\OriginalVerbatim=\Verbatim
\renewcommand{\Verbatim}[1][1]{
    \def\FV@Space{\discretionary{}{}{something} }
    \OriginalVerbatim[#1]}
\makeatother
    
\begin{document}

\begin{Verbatim}[]
hello world
\end{Verbatim}

\end{document}

Tectonic's output is:

Running TeX ...
(Untitled.tex
LaTeX2e <2018-04-01> patch level 4
Babel <3.20> and hyphenation patterns for 84 language(s) loaded.
(article.cls
Document Class: article 2014/09/29 v1.4h Standard LaTeX document class
(size10.clo)) (fancyvrb.sty
Style option: `fancyvrb' v2.7a, with DG/SPQR fixes, and firstline=lastline fix 
<2008/02/07> (tvz) (keyval.sty))
No file Untitled.aux.

and then just hangs.

[ralismark]

Running gdb (gdb target/debug/tectonic, r -p input.tex, then ctrl-c when it hangs), it appears that the tex engine gets stuck in this loop. Neither of the ifs get run. Here are some relevant values, copied from gdb:

• main_pp = 525
• main_ppp = 525
• is_char_node(main_ppp) = false
• mem[main_ppp] = {b32 = {s0 = 655360, s1 = -268435455}, b16 = {s0 = 0, s1 = 10, s2 = 1, s3 = 61440}, gr = -3.1050391462465209e+231, ptr = 0xf0000001000a0000}

I'm not familiar enough with the how the tex engine works to figure out what's causing this.

[pkgw]

Thanks for the investigation @ralismark ! The TeX engine should really not have any bugs of this nature, so this probably indicates a mistake in my translation of the core code. For these kinds of issues I usually end up consulting the book and trying to trace through what's going on to see where I went wrong.

I hope to be able to take a deeper look at this myself, but my main priority is to get a TeXLive 2020 update rolled out.

[pkgw]

Fixed by #666 it seems!