Hi everybody!
Assume that the files testa.pdf, testb.pdf and testc.pdf exist.
Further assume there is a file mwe.tex:
\NeedsTeXFormat{LaTeX2e}
\documentclass[12pt]{letter}
\usepackage{shellesc,graphicx}
\begin{document}
\includegraphics{testa.pdf}\newpage
\includegraphics{testb.pdf}\newpage
\includegraphics{testc.pdf}\newpage
\immediate\write18{ lsof | grep latex | grep test | less -S }
\end{document}
If (on a linux system) you execute
lualatex --shell-escape mwe
and
xelatex --shell-escape mwe
you see a difference: the included pdf files are open if you use
lualatex, they are _not_open_ when xelatex is used.
That difference is not a problem if you want to include only a few
files, but it is a problem if you want to include a few thousands
of pdfs - on most sytems there is a limit of about 1024 open files.
That limit can be raised, but at least in my case that does
not really help: using write18 to start a program when many file
descriptors are open might expose a bug in the c++ library if "many"
is "more than 1023". If that child uses execve() to start another child,
that execve fails with a "*** buffer overflow detected ***" message.
Is this is a problem of luatex? I don't know, but I think it is.
Keeping all files that are included by \includegraphics open is a
wasteful use of limited system resources (file descriptors) , and xetex
demonstrates that it is not necessary.
BTW: In my tests xelatex fails to include more than 5005 pdfs correctly.
Pdfs 5005+ are read, white space is reserved, but the actual content of
the included pdfs is missing. Nothing unusual is written to the log.
System used:
* Linux, 64bit (i4790K, 32GB)
* OpenSuSE Tumbleweed
* LuaTeX, Version 1.0.4 (TeX Live 2017/TeX Live for SUSE Linux)
* XeTeX 3.14159265-2.6-0.99998 (TeX Live 2017/TeX Live for SUSE Linux)
Knut
