[Groff] soelim and file names defined in string registers

[Joerg van den Hoff]

hi,

looking at the docs and the archives I did'nt find this:

if there are preprocessor directives in a sourced file and the file name 
is specified  in a string register in the document errors result.

say I have to files `t2' and `t3' which are to be sourced from within 
this document `t1':

==============
.ds fname t3
.so t2
.LP
.so \*[fname]
==============

difference is that `t3' is specified in a string register. running 
`soelim' on this yields in the example (t2, t3 containing some pic stuff):
===================================
.lf 1 ./t1
.ds fname t3
.lf 1 ./t2
sourced file's name specified as text.
.PS
boxwid = 0.5
box
down
box
.PE


.lf 3 ./t1
.LP
.so \*[fname]
=========================================

i.e. `t2' is already included, but the second `.so' is not yet 
expanded(or what???). formatting this (or the orignal `t1') with 
something like

groff -s -ms -p -X t1

generates the error:

t3:2: macro error: bad arguments to PS (not preprocessed with pic?).

without preprocessor stuff in the sourced files, everything seems to 
work (ms macros do no harm, for instance).

could someone, please, explain what exactly the problem is (or tell me 
to RTFM on page xxx...)? even better would be a solution/ work around 
how to specify file names of sourced files via variables/string 
registers from within the document (the -I option is not what I'm 
looking for)

many thanks

joerg