Undefined control sequence \ifluatex when using document class comjnl.cls

Question

I am trying to compile a LaTeX into PDF with TexStudio and MikTek 2.9 on my windows 10 PC:

\documentclass{comjnl}
\usepackage{amsmath}
\begin{document}
    x
\end{document}

but I systematically get an error at line 189 of pdftexcmds.sty:

! Undefined control sequence.
l.189 \ifluatex

In the logs, I also see:

LaTeX Warning: You have requested, on input line 186, version
  `2019/11/07' of package iftex, but only version
  `2013/04/04 v0.2 Provides if(tex) conditional for PDFTeX, XeTeX,
  and LuaTeX' is available.

I have just reinstalled MikTex from scratch. The installed iftex version has been packaged on 10/11/2019.

Is this a bug? How can I solve this?

P.S. This issue does not happen when I use document class article or when I don't use package amsmath.

your miktex is not up-to-date, you are either missing the new version of the iftex package or an older version is interfering. Check for updates as user and as admin, and also check for new, not installed packages in both modes. — Ulrike Fischer, Dec 07 '19 at 18:10
Out topic: but note that, hopefully comjnl.cls was not created based on lualatex, please take care... — MadyYuvi, Dec 27 '19 at 12:44

score 0 · Accepted Answer · answered Dec 07 '19 at 18:39

0

Following Ulrike's comment, I had not performed updates as a user (but I had done it as an admin). Then, I had to install iftex, refresh the database via MikTex's console and the issue is now gone.

answered Dec 07 '19 at 18:39

Jérôme Verstrynge

125

score 0 · Answer 2 · edited Dec 27 '19 at 12:35

I had the same issue where adding any \usepackage{<packageName>} before the \begin{document} statement would lead to the above error. I tried installing pdftexcmds and iftex packages by

mpm --admin --install=<packageName>

in a terminal with admin privileges, but it didn't help.

What I ended up doing was to uninstall the MiKTeX I had installed via Chocolatey by choco uninstall miktex and then uninstall the second MiKTeX installation which was still in my C:\Program Files\MiKTeX 2.9\miktex for some reason!. then I deleted the MiKTeX folders in:

C:\Users\<userName>\AppData\Roaming
C:\Users\<userName>\AppData\Local

and then I reinstalled MiKTeX through chocolatey by

choco install MiKTeX

it seems that my MiKTeX installation was messed up and a complete uninstall and a fresh reinstallation solves the above weird error!

Undefined control sequence \ifluatex when using document class comjnl.cls

2 Answers2

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