[ns] Tcl command returned bad code error

[Sean Murphy]

Hi,

I'm having problems running my test scripts through my version of ns. The
problem that occurs appears to be some kind of low level tcl problem: the
return value from the tcl interpreter appears to be invalid and I get the
very cryptic "command returned bad code" error.

I've been working on this for a couple of days and I can't seem to pin
down the problem - I guess this can be attributed to the fact that I'm not
very clued in on tcl. I decided to upgrade my tcl interpreter hoping that
the problem would go away before I started digging around in the tcl
source code, but to no avail. (Incidentally, I've got some notes on how to
compile ns-2.1b6 with tcl 8.3.1 - only a couple of small changes are
necessary - I'll put them on the web once I've run validate fully for the
resulting binary).

Upgrading to tcl 8.3.1 did cause a slight behavioural change - now instead
of printing the "command returned bad code" error, it simply stops and
prints out the result obtained from calling a particular tcl function.

I could give details on what exactly my script is trying to do and how
I've modified ns, but I think that this would require quite a bit of
detailed explanation and I'm not so sure that it would be very
illuminating. What is important, however (I think), is that I'm nesting
tcl and c++ and tcl; so, for example, I run the tcl script and this calls
some c++ code (using $objname cmd command-name params). This c++ function
then calls tcl.eval() to evaluate some more (O)tcl code and this is where
the problem arises.

I was wondering if anyone has observed this problem before - if so, what
caused it and how was it solved? I was thinking that it may be to do with
the fact that tclcl uses Tcl_GlobalEval and that this does not permit such
nesting but calling tcl from c++ seems to be performed in many places, so
now I don't think that this is the problem.

Any pointer/hints/tips appreciated.

Regards,
Sean.

-----
Sean Murphy,			Email: sean.murphy@teltec.dcu.ie
Teltec Ireland,			Phone: +353-1-7045080
DCU, Dublin 9,			Fax:   +353-1-7045092
Ireland.