Why is `openin_any = p` restricting access to packages in TEXMFDIST?

[Phelype Oleinik]

Hi Akira,

On Wed, Sep 23, 2020 at 7:54 PM Akira Kakuto <kakuto at w32tex.org> wrote:
>
> On 2020/09/24 5:56, Adrian wrote:
> > According to my TeX Stack Exchange question [1], a minimal document triggering the
> > error is \documentclass{article}\usepackage{xparse}\begin{document}\end{document}
>
> Probably, it is due to changes in latex.

It is related to how LaTeX determines if a file exists, yes:  some time
ago we changed from \openin...\ifeof to looking at the output of
\pdffilesize to determine if a file exists.  But it is not LaTeX's
fault: \pdffilesize fails with the same error using plain:

    export openin_any=p && pdftex '\pdffilesize{sample2e.tex}\bye'

Best,
Phelype