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From: hollen@spot.megatek.uucp (Dion Hollenbeck)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Calling a "C" function from assembly language
Message-ID: <391@megatek.UUCP>
Date: 25 Oct 88 19:01:55 GMT
References: <5876@killer.DALLAS.TX.US>
Sender: news@megatek.UUCP
Reply-To: hollen@megatek.UUCP ()
Organization: Megatek Corporation, San Diego, Ca.
Lines: 26

From article <5876@killer.DALLAS.TX.US>, by cy@killer.DALLAS.TX.US (Cyrus Foughty):
> 
> 	I have a assembly language program from which I want to 
> 	call a "C" function. I know this is backwards from what 
> 	everyone else does. BTW, I am using Microsoft Masm and
> 	"C" 5.1 for this little dodad. [...stuff deleted...]
> 	How do I do it?

The key is in the mixed language section of the C reference manual,
although it is implied rather than stated exactly.  You need to know
that a C function pushes its parameters on the stack from right to
left.  Byte width parameters are pushed as words with high order
bits zeroed and long width (32-bits) parameters are pushed high
16-bits first and low 16-bits second.  The calling assembly
is responsible for stripping the pushed parms off the stack on
return from the called function.  I recommend using "ADD  SP,xxx"
where xxx = number of words to strip from stack (remember bytes
went on stack as words).



	Dion Hollenbeck             (619) 455-5590 x2814
	Megatek Corporation, 9645 Scranton Road, San Diego, CA  92121

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