Switches and options for writing OS/2 device drivers with Borland C  
3.1 and 4.0C, courtesy of Rich Peters, 76236,2554

-3 -A- -c -f- -K -ms! -pr -R -O -Oabcilpvs-t -y -z

This gives you 386 small model code, SS!=DS, and register calling 
conventions. Also, this is pretty aggressive optimization, so volatile 
must be used for testing things like the done bit, etc. BC 3.1 has a bug 
with long parameters and register calling conventions, so I prototype 
any function with a long param for the first two parameters as pascal. 
(long means 32-bit length, not a C type). BC4 doesn't have this bug, 
but it doesn't do 32-bit multiplies or divides, so I don't use it.

For the Microsoft 8.00 compiler:

/AS /Gs /Oacilntw /Apl /f- /G3r

This gives you 386 small model code, SS!=DS, 1 byte packing, and 
register calling conventions. Again, volatile must be used for testing 
things like the done bit, etc. You will get missing externals for 
_anulmul, etc., but these are bogus, as they are never called. You 
could link with the MSC 6.0 SLIBCEP to get rid of them, or stub 
them out with int 3's, as I do.

With either compiler, turning on any sort of global optimization kills 
your DD, so I never use these. The above optimizations are the most I 
can turn on with my DDs and still have them work.

I use a short assembler stub first to get the segments in the correct 
order:

_DATA	segment	dword	public	'DATA'	
_DATA	ends

CONST	segment	dword	public	'CONST'
CONST	ends

_BSS		segment	dword public 'BSS'
_BSS		ends

_ALGN	segment	para	public	'CODE'
_ALGN	ends

_TEXT	segment	public	'CODE'
_TEXT	ends

EndCode	segment	public	'CODE'
EndCode	ends