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From: blarson@skat.usc.edu (Bob Larson)
Newsgroups: comp.unix.wizards,comp.lang.c
Subject: Re: Needed:  A (Portable) way of setting up the arg stack
Keywords: 1/varargs, callg
Message-ID: <17606@usc.edu>
Date: 4 Jun 89 17:43:33 GMT
References: <708@mitisft.Convergent.COM> <32208@apple.Apple.COM> <10354@smoke.BRL.MIL> <11830@bloom-beacon.MIT.EDU>
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In article <11830@bloom-beacon.MIT.EDU> scs@adam.pika.mit.edu (Steve Summit) writes:
>va_call can be implemented in one line of assembly language on
>the VAX; it typically requires ten or twenty lines on other
>machines, to copy the arguments from the vector to the real stack
>(or wherever arguments are really passed).  I have implementations
>for the PDP11, NS32000, 68000, and 80x86.  (This is a machine
>specific problem, not an operating system specific problem.)

??? Then how come my os9/68k compiler for the 68020 uses a different
calling convention than the sun 3 compiler?  This problem is most
definitly dependant on the calling convention your compiler happens
to be using at the moment, which can vary with cpu, operating system,
and even compiler options.

> A
>routine such as va_call MUST be written in assembly language; it
>is one of the handful of functions I know of that cannot possibly
>be written in C.

This almost sounds like a chalange to find a machine where it can be
done in non-portable C.  I'm sure there is one out there somewhere.

-- 
Bob Larson	Arpa:	blarson@skat.usc.edu
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