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From: Rich Felker <dalias@aerifal.cx>
To: musl@lists.openwall.com
Subject: Re: Conformance issues to address after 0.9.12 release
Date: Tue, 13 Aug 2013 00:25:02 -0400	[thread overview]
Message-ID: <20130813042502.GC221@brightrain.aerifal.cx> (raw)
In-Reply-To: <20130813034555.GF5368@port70.net>

On Tue, Aug 13, 2013 at 05:45:55AM +0200, Szabolcs Nagy wrote:
> * Rich Felker <dalias@aerifal.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


      reply	other threads:[~2013-08-13  4:25 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-07-29  6:34 Rich Felker
2013-07-29 16:00 ` Szabolcs Nagy
2013-07-29 21:04   ` Rich Felker
2013-07-30  2:26     ` Szabolcs Nagy
2013-08-12 19:27       ` Szabolcs Nagy
2013-08-13  3:32         ` Rich Felker
2013-08-13  3:45           ` Szabolcs Nagy
2013-08-13  4:25             ` Rich Felker [this message]

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