index completely messed up in dtx file

Question

I fight with the strange and useless entries of the index in dtx files.

It can reproduced with

% \iffalse
%<*driver>
\ProvidesFile{dtxcode.tex}
%</driver>
%
%<*driver>
\documentclass{ltxdoc}
\EnableCrossrefs
\CodelineIndex
\RecordChanges
\listfiles

\begin{document}
  \DocInput{dtxcode.tex}
  \PrintIndex
\end{document}
%</driver>
% \fi
%%
% \DescribeMacro{\foobar} Prints out foobar
% 
% \Finale
\endinput

the result is

foobar= \subitem *+\foobar+, \usage{1}

printed as shown here in the pdf.

Anyway: I would like to switch of the index functionality of doc.sty completely and replace it with my own. It tries to add EVERY latex command used in the index. With my current code this is hundrets of entries which have nothing to do with any command defined by the package.

Answer 1

If I run

makeindex -s gind.ist dtxcode

the content of the resulting .ind file is

 \begin{theindex} 
 \makeatletter\scan@allowedfalse
{\bfseries\hfil F\hfil}\nopagebreak

  \item \verb*+\foobar+\pfill \usage{1}

 \end{theindex}

If instead I run the wrong command

makeindex dtxcode

the resulting file contains

\begin{theindex}

  \item foobar=\verb
    \subitem *+\foobar+, \usage{1}

\end{theindex}

which is obviously wrong.

Indexing of a macro is suppressed by adding it as the argument to a \DoNotIndex command (there can be many, each receiving lists of macro names); for instance (from one .dtx of mine)

% \DoNotIndex{\newcommand,\newenvironment,\!,\@empty,\@gobble,\@gobbletwo}
% \DoNotIndex{\@ifpackageloaded,\@ifpackagewith,\@ifundefined,\@namedef}
% \DoNotIndex{\@nil,\@onlypreamble,\@tempa,\@tempb,\@tempswafalse,\def}

(I like that one command doesn't spill over the next line.)

It's customary that a DTX file has the .dtx extension, rather than .tex