bug#21595: 11.88.8; TeX help in Plain contaminated by LaTeX

[jfbu]

Hi Mosè

Le 1 oct. 2015 à 14:06, Mosè Giordano <address@hidden> a écrit :

> Hi Jean-François,
> 
> 2015-10-01 7:24 GMT+02:00 jfbu <address@hidden>:
>> Remember to cover the basics, that is, what you expected to happen and
>> what in fact did happen.
>> 
>> The following TeX source file
>> 
>>    \def\foo{\begingroup\foo}\foo
>> 
>>    \bye
>> 
>> when run from a TeX-mode Emacs/AUCTeX buffer generates on C-c `,
>> after compilation has halted on a TeX capacity exceeded error,
>> a buffer displaying a long text of which I reproduce only the start
>> here:
>> 
>> ERROR: TeX capacity exceeded, sorry [grouping levels=255].
>> 
>> --- TeX said ---
>> \foo ->\begingroup
>>                   \foo
>> l.1 \def\foo{\begingroup\foo}\foo
>>                                 --- HELP ---
>> TeX has just run out of space and aborted its execution. Before you
>> panic, remember that the least likely cause of this error is TeX not
>> having the capacity to process your document.  It was probably an
>> error in your input file that caused TeX to run out of room. The
>> following discussion explains how to decide whether you've really
>> exceeded TeX's capacity and, if so, what to do. If the problem is an
>> error in the input, you may have to use the divide and conquer method
>> described previously to locate it. LaTeX seldom runs out of space on a
>> short input file, so if running it on the last few pages before the
>> error indicator's position still produces the error, then there's
>> almost certainly something wrong in the input file.
>> 
>> The end of the error indicator tells what kind of space TeX ran out
>> of. The more common ones are listed below, with an explanation of
>> their probable causes.
>> 
>> buffer size
>> ===========
>> Can be caused by too long a piece of text as the argument
>> 
>> [continued]
>> 
>> The rest of the text has many many references to LaTeX.
>> 
>> As the context here is Plain TeX this longish info is mostly
>> irrelevant (it provides useful information to average LaTeX
>> users, but nothing spicy to well trained macro programmers ;-) )
>> 
>> For some years I thought that the message originated in the
>> help system of the tex binary itself (my Emacs is configured
>> actually to run etex not tex if that matters), but it appears
>> that I could very well
>> have erred completely. I of course realized Knuth would not
>> have included such a message, but perhaps the binaries of
>> my TeXLive installation did provide an extended help system.
>> 
>> A guru from the LaTeX3 team tells me it can't be the case,
>> thus my question is
>> 
>>   Does the message somehow come from AUCTeX ?
> 
> Yes, AUCTeX has help messages builtin in `TeX-error-description-list'
> variable, seemingly provided by someone called Leslie Lamport [1],
> maybe you've heard about him.   These messages are sometimes more
> verbose and useful than help messages present in log file.  If AUCTeX
> can't find help messages in its database, falls back on log file.
> Probably all those reference to LaTeX come from Lamport.
> 
> Being `TeX-error-description-list' a variable I'm not sure to have it
> would be easy to have different values for different modes (plain
> TeX/LaTeX/you name it).
> 
> Bye,
> Mosè
> 
> 
> Reference:
> [1] 
> http://git.savannah.gnu.org/gitweb/?p=auctex.git;a=blob;f=doc/history.texi;hb=HEAD

Thanks for confirming that this comes from AUCTeX incorporating
probable contributtions of Leslie Lamport. For bystanders
here are a few more lines of the help message.

> buffer size
> ===========
> Can be caused by too long a piece of text as the argument
> of a sectioning, \caption, \addcontentsline, or \addtocontents
> command. This error will probably occur when the \end{document} is
> being processed, but it could happen when a \tableofcontents,
> \listoffigures, or \listoftables command is executed. To solve this
> problem, use a shorter optional argument. Even if you're producing a
> table of contents or a list of figures or tables, such a long entry
> won't help the reader.


this information is 100% LaTeX and presents no interest for users of
other formats. It is somewhat informative to users of the LaTeX macros
although it may be obsolete by now because the TeX memory parameters
have been considerably increased in the distributions like TeXLive
and MikTeX since the eighties.

This is not a big issue, naturally.

However you may keep this in mind if one day before the 22th
century LaTeX3 starts being widely used, perhaps that will
mean then a need for a complete rewrite of the format error
messages.

I have my answer, thanks a lot.

best
Jean-François