lacheck is confused when curly brackets are inside a \newcommand

Karl Berry karl at
Sun May 1 00:18:28 CEST 2022

Hi Michael - thanks again for the report.

    \newcommand{\boldx}[1]{{\bf #1}}
    "foo.tex", line 1: <- unmatched "}"

The immediate problem was that the { that starts the definition was
swallowed up by the pattern that started the definition. Hence the {
vs. } count mismatch. That is easy enough to fix, by incrementing the
count an extra time at the beginning.

Then there was a second problem that if a } was missing, no error was
reported. That is, if the def_group variable counting braces wasn't zero
at the end of the file. So I added:
<<EOF>> { 
	  if (def_count != 0)
	  	printf("\"%s\", line %d: %d missing right brace(s).\n",  
			file_name, line_count, def_count);

Then I noticed that the pattern matching \newcommand etc. did not try to
handle the * form of definitions, or the [N] argument count, or the
[dflt] optional argument default. Foolishly, I tried to add all that.
The regular expression is now pretty much a monster. (Unfortunately
[f]lex does not support "readable" regexps as in Perl's /x, as far as I

I feel almost certain that I introduced bugs somewhere in all that.
Here is what the regexp looks like now, together with a sort-of "human
translation" of the pieces I wrote for myself.

"\\"(provide|(re)?newcommand)[ \t\n]*(\*[ \t\n]*)?(\{\\[^}]+\}|\\([a-zA-Z]+|.))[ \t\n]*(\[[0-9]\](\[[^]]*\])?)?[ \t\n]*[^{]*\{	{ ++def_count; BEGIN(DEF); }

  /*                          ws     optional*    ({\cs}      |\cs)                     [N]?      [dflt]?             .*     {defn}
  ... */

I committed the changes in TL r63190, and bumped the lacheck version to 1.30.

I don't want to commit a new binary, but I made one for x86_64-linux and
put it at for anyone who'd like
to give it a try. It doesn't depend on kpathsea or anything else, so
should be ok to just download and run from wherever.


P.S. If anyone wants to really take over lacheck maintenance, that
would be most excellent.

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