🚀 go-pugleaf

I need some serious help understanding the calling of 16 bit code.
I'm using the DosMonXxx calls to create a printer monitor that
intercepts printer output.  It has worked fine on occasion, but every
time I make a modification I experience a different bug or an
occasional success.  Because of this I suspect that it has something
to do with byte alignment or addresses, something that might shift
when code is added or changed.  

The calls are being packaged in a DLL which is used by several
executables.  At times they were successful in some .exe's but not in
others.  Now they uniformly fail on the DosMonOpen().

I have the DosMon calls prototyped as follows:

typedef SHORT HFILE16;
typedef HFILE16 *PHFILE16;

APIRET16 APIENTRY16 Dos16MonRead  ( PUCHAR, USHORT, PMONITORPACKET, PUSHORT);
APIRET16 APIENTRY16 Dos16MonWrite ( PUCHAR, PMONITORPACKET, USHORT);
APIRET16 APIENTRY16 Dos16MonOpen  ( PSZ, PHFILE16);
APIRET16 APIENTRY16 Dos16MonClose ( HFILE16);
APIRET16 APIENTRY16 Dos16MonReg   ( HFILE16, PUCHAR, PUCHAR, USHORT, USHORT);

Lately I've been getting an error on the first DosMon function
called, Dos16MonOpen().  It returns 380, which means Invalid Device
Name.  I've tried "lpt1", "lpt1:", "lpt2", and others.  Yet I know
it's not the actual name that's wrong because this call has succeeded
before.

For a while a couple of days ago, this call always succeeded, but the
next call, Dos16MonReg() failed with an error code of 379, Invalid
Parameters.

Is there something special I have to do to the parameters to make
them usable by the 16-bit functions?  Or does the compiler do that
automatically when it sees APIENTRY16 in the prototype?  By the way,
I'm using the C/Set++ 2.1 compiler, and running this under OS/2 2.1.

Any help would be ***greatly*** appreciated.  In the US and Cananda,
call me collect if you like from 11 AM to 6 PM eastern time at (703)
941-5952.  Electronic responses are also welcome.

Sweating,  
Keith

-- 
--------------------------------------------------------------------------
Keith Bennett                             Bennett Business Solutions, Inc.
Silver Spring, MD USA                     OS/2 & DOS Software Development
kbennett@cpcug.org                        (301) 871-7696