🚀 go-pugleaf

I'm having a problem with TSR programming with MSC.  My final goal is
write something which catches DOS int 21 read string so that you can
do history and file completetion.

So I started out by writing a TSR which gets activated from int 60H.
The interrupt handler calls a simple c function (_interrupt type) via
a jmp (This was done because MSC automatically inserts a return from
interrupt after the fucntion completes).  The c function only contains
1 printf statement.  When I generate the int 60H from the program
which installed the int 60H interrupt, everything works fine.  But
after I TSR the handler and generate int 60H from debug, the print
statement prints out garbage and then returns.

I am just about positive that this is NOT a re-entrant problem.  I
know at the time that the int 60H is occuring that the cpu is
executing my code, not dos, so it can't be re-entering dos.  This
leads me to believe that there's something going wrong with the printf
library function.  I traced through the beginning of the printf
fucntion and saw that it did get the correct pointer to the string
that it was supposed to print, and the string still contained the
correct data.  So I'm beginning to belive that I need to do somekind
of environmental restoration in order to get the c library to behave 
correctly.  But I don't know what needs to be done.  I tried restoring
various register values but none of this helped.

So I would like to know if my guess is correct in that the c library
needs some pointers restored.   If so, which library functions are
affected (i.e. is only the print routines?).  Also what needs to be
done to restore the environment?

Many thanks,

Sandy
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			    Sandy Spinrad
		   Internet: spinrad@cornu.ucsb.edu
 		 UUNET: uunet!hub.ucsb.edu!spinrad@cornu