bug#65628: Document preview fails with long filenames

[John Holman]

Have to say this explanation seems unlikely to me at first sight. File path limit MAX_PATH is 260 but here we have C:\Users\johng\temp\textest\01234567890123456789012.tex which is only about 50. Routinely deal with much longer paths than this using windows without a problem. Similarly max command length for cmd.exe is 8182, the underlying API limit is 32767 - and you can see the full command to pdflatex echoed in the log so it's obviously getting through - so that also seems unlikely.

On Wed, 30 Aug 2023 at 18:35, David Kastrup <dak@gnu.org> wrote:

John Holman <john.g.holman@gmail.com> writes:

> Hi. I'm not sure that the problem was captured in the log below created
> by preview-report-bug so a few more details first:
>
> Running auctex on windows 11 with MiKTeX
>
> Test file contents (but most files containing maths seem to trigger the
> problem)
>
> \documentclass{article}
> \begin{document}
>
> \(x=y\)
>
> \end{document}
>
> Document preview works when the filename has no more than 22 characters,
> e.g. test.tex, but fails with message "Ghostscript filter: No bounding box"
> when the filename has more, e.g. 01234567890123456789012.tex. However
> buffer preview always works.
>
> When document preview fails the maths sections are replaced with the
> roadworks signs indefinitely. The 01234567890123456789012.prv directory is
> created
> containing a temp folder containing a preview.dsc file but no png
> images. The rungs.exe and mgs.exe processes don't exit until killed manually
> or emacs is closed.
>
> The contents of the *.. output* buffer are then
>
> Running `Preview-LaTeX' on `012345678901234546789012' with ``pdflatex
>  -file-line-error
>  "\nonstopmode\nofiles\PassOptionsToPackage{active,tightpage,auctex}{preview}\AtBeginDocument{\ifx\ifPreview\undefined\RequirePackage[displaymath,floats,graphics,textmath,sections,footnotes]{preview}[2004/11/05]\fi}"
> "\input" "\detokenize{" "012345678901234546789012.tex" "}"''

Probably exceeding a total command line length of 256 characters or some
similar Windows restriction.  I also seem to remember that some Windows
file system or API limited the length of absolute filenames you could
access even when only using relative filenames, so the length of the
directory path you are in might also play a part here.

--
David Kastrup