Re: smallest possible testfile for mpgraph-error?

[Taco Hoekwater <bittext@quicknet.nl>]

Patrick Gundlach wrote:
> 
> Now I rename simple.mp to mpgraph.mp:
> 
> with \protectbufferstrue, mpgraph.1 is ok.

lots of stuff can go wrong with names like mpgraph.mp.

(at least one of them is the shell itself: it caches
i-node numbers, and I've had similar problems with
totally non-TeX related files if and only if the file
was opened for writing without actually unlinking it.
This may not be the problem here, but it is nevertheless
possible).

> mpgraph.mp has been renamed to tmpgraph.kep, then overwritten by 
> something (this I dont know, probably the same as above 
> (beginfig(1)...)  + "end.").

This is texexec: in the subroutine 'checkMPlabels'

> Then mpto opens mpgraph.mp (55 bytes), writes it to tmpgraph.tex). Then \\end is appended > to tmpgraph.tex. 

probably mpto

> After that, pdftex is called to create tmpgraph.dvi (208 bytes). 
> !! But just before creating the dvi 
> file, mpgraph.mp gets overwritten with a single   
> "end." line. 

This is context itself, that is called to generate the label.
because it doesn't know about protected buffers, it writes
mpgraph.mp. Context does this *always* nowadays, even on the
following sequence of commands:

touch test.tex
texexec test
[press control-d]

The problem is in \initializeMPgraphics, which is part of
\everyjob. The following definition would be a lot safer:

\def\initializeMPgraphics%
  { \immediate\openin\scratchread\MPgraphicfile.mp
    \ifeof\scratchread
      \immediate\closein\scratchread
    \else 
     \immediate\openout\MPwrite\MPgraphicfile.mp
     \immediate\write\MPwrite{end.}%
     \immediate\closeout\MPwrite
   \fi
   \immediate\closein\scratchread
   }

I don't see any obvious reason why \protectbufferstrue
shouldn't be the default, btw.

Greetings, Taco