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Message-ID: <20130813042502.GC221@brightrain.aerifal.cx>
Date: Tue, 13 Aug 2013 00:25:02 -0400
From: Rich Felker <dalias@...ifal.cx>
To: musl@...ts.openwall.com
Subject: Re: Conformance issues to address after 0.9.12 release
On Tue, Aug 13, 2013 at 05:45:55AM +0200, Szabolcs Nagy wrote:
> * Rich Felker <dalias@...ifal.cx> [2013-08-12 23:32:32 -0400]:
> > Why the push/pop? Is there a reason you can't just store over top of
> > the argument slot at 4(%esp) or even below the stack pointer at
> > -4(%esp)? The latter would be unsafe if you ever wanted to read back
> > the value since it could be clobbered asynchronously by a signal
> > handler, but you don't want/need to read it back anyway.
>
> ah ok
> did not know the callee can modify those
Yes, the argument zone on the stack belongs to the callee. This is
what makes tail calls possible; otherwise the only functions you could
tail-call to would be ones that take no arguments. (Of course you can
only tail-call to a function that takes the same or less space for its
arguments.)
Rich
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