[tex-live] texlive perl

[Reinhard Kotucha]

On 21 April 2010 T T wrote:

 > On 14 April 2010 23:53, Lars Madsen <daleif at imf.au.dk> wrote:
 > > On WinXP:
 > >
 > > it simply says, "Internal error occured" (or similar, this laptop
 > > is runing in danish)
 > >
 > > AR 9
 > >
 > > it suggests sending MS an error report, along with it an error
 > > report with a lot of odd information
 > >
 > > The offending command
 > >
 > > latexmk -pdf -pv test.tex
 > >
 > > for some compilable test.tex
 > 
 > The problem seems to be with Perl.  I can't start AR9 from Perl at
 > all, always the same error as you see.  What's even more bizarre, I
 > can't start AR9 from any child process started from Perl!  So there
 > is something that is inherited from the perl.exe process that
 > causes AR to crash, but I have no clue what it might be and I
 > couldn't find anything suspicius in Perl's sources regarding
 > process spawning.  I'm out of ideas I'm afraid.

It's probably not Perl specific.  We encountered the same problem with
the texlua wrapper for texdoc.  We first assumed that the argument
vector had not been passed properly to AR.  I then read all the
related mails again carefully and found an interesting hint: The error
doesn't occur when AR is already running.  This means that the
argument vector can't be the culprit.  On the other hand, Manuel found
out that it made a difference whether the wrapper passed the arguments
as a list (os.spawn()) or as a string (os.execute()).

os.execute() is a Lua function which expects a string as an argument
and calls system(3) in order pass the request to a shell.  os.spawn()
is a function gratefully provided by Taco.  It passes its arguments as
a list to execvpe(3).

The Perl function system() also supports both, system(3) and
execvpe(3).  However, Perl tries to be smart, which makes debugging a
bit harder.  If you provide a string, system() always passes the
string to a shell.  If you provide a list, Perl decides itself whether
system(3) or execvpe(3) is more appropriate.

On Unix, execvpe() simply passes the argument list to the program it
executes.  On Windows, however, it converts the list to a string and
then the string back to a list again.  Of course, this breaks
arguments containing space characters.  The workaround is to quote
each argument.

The difference between Perl and texlua is that Perl automatically
quotes all arguments before they are passed to execvpe(3) while in
texlua you have to quote arguments yourself.  Under Windows at least.

If you can reproduce the problem with texlua, I think that debugging
is much easier because Lua is tiny.

However, I suppose that it's a Windows problem, quite unrelated to
Perl or texlua.  How execvpe() is implemented under Windows is
completely braindead and error-prone.

Another approach is to ask Adobe under which circumstances the error
message "Internal Error" is raised.  It's probably difficult to get in
contact with Adobe developers.  But you could ask Leonard Rosenthol.
I remember him as a maintainer of the PDF backend of ImageMagick but
for 3 or 4 years he is employed by Adobe as a PDF guru.  He's quite
open to TeX-related problems.

Regards,
  Reinhard

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Reinhard Kotucha			              Phone: +49-511-3373112
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