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SubjectRe: Where is it written?
Followup to:  <>
By author: Peter Samuelson <>
In newsgroup:
> [Andrea Arcangeli]
> > Can you think at one case where it's better to push the parameter on
> > the stack instead of passing them through the callee clobbered
> > ebx/eax/edx?
> Well it's safer if you are lazy about prototyping varargs functions.
> But of course by doing that you're treading on thin ice anyway, in
> terms of type promotion and portability. So I guess it's much better
> to say "varargs functions MUST be prototyped" and use the registers.

It definitely is now. At the time the original x86 ABI was created, a
lot of C code was still K&R, and thus prototypes didn't exist...

> AIUI gcc can cope OK with multiple ABIs to be chosen at runtime, am I
> right? IRIX, HP-UX and AIX all have both 32-bit and 64-bit ABIs.

I don't think we want to introduce a new ABI in user space at this
time. If we ever have to major-rev the ABI (, then we
should consider this.

<> at work, <> in private!
"Unix gives you enough rope to shoot yourself in the foot."
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