Path: utzoo!attcan!uunet!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!mips!gumby
From: sah@gumby (Steve Hanson)
Newsgroups: comp.sys.mips
Subject: Re: Question on cc
Message-ID: <40299@mips.mips.COM>
Date: 20 Jul 90 15:50:42 GMT
References: <Uad7TRa00XMV43XHQF@cs.cmu.edu>
Sender: news@mips.COM
Reply-To: sah@gumby (Steve Hanson)
Organization: MIPS Computer Systems, Sunnyvale CA
Lines: 59
In-reply-to: David.Steere@CS.CMU.EDU

In article <Uad7TRa00XMV43XHQF@cs.cmu.edu>, David.Steere@CS writes:
>BACKGROUND:
>
>I'm porting a file system to the Dec 3100. Our code is mostly written in
>C++, which gets precompiled (as it were) into standard  C.
>The pmax C compiler is standard C (pcc), so for the most part, this
>isn't a problem. 
>
>However,  we are having a problem with procedures with a variable 
>number of arguments (like printf). Typically, when such a procedure is
>called, the parameters are read off the stack, using a pointer to the
>first argument to reference the other arguments. This assumes that
>the arguments are written to the stack.  Syntactically, variable length
>procedure headers can be declared by including <varargs.h>, and having
>the last argument be va_alist. varargs.h declares various macros
>which basically handle the referencing to the stack.
>
>In the Pmax compiler, the first several arguments are not written onto
>the stack automatically. So they are not found when the procedure is
>called. It turns out that the compiler looks for the symbol "va_alist" in
>the procedure header, and if it is found forces all the arguments to be
>written to the stack. Okay, this seems like a hack and it seems to work
>fine, except that we use C++, which during preprocessing renames all the
>variables, prepending things like au0_ on the front of variable names.
>So va_alist is now au0_va_alist. Since that isn't the same as va_alist,
>the compiler does not force all the arguments to the stack.
>
>QUESTION:
>Is there a way to tell the compiler to force arguments to the stack for
>a 
>particular routine?
>
>thanks,
>
>david.


Two suggestions:

1) Bypass the name problem by declaring these functions with 
   ellipsis notation:

	void foo(int c, ...) {}

and ask your translator to produce ANSI C syntax, e.g.
	/* <<AT&T C++ Translator 2.00 06/30/89>> */
	CC +a1 foo.c

2) Use the native cpp to give you your name back, e.g.

CC  -Wp,-D__0va_alist=va_alist foo.c

or in your case

CC  -Wp,-Dau0_va_alist=va_alist foo.c
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