From mboxrd@z Thu Jan  1 00:00:00 1970
From: Wincent Colaiuta <win@wincent.com>
Subject: Re: [PATCH v4] gc: call "prune --expire 2.weeks.ago" by default
Date: Thu, 13 Mar 2008 10:48:50 +0100
Message-ID: <7FB80115-C1E4-4F83-9374-41AB1BDA0579@wincent.com>
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Cc: Johannes Schindelin <Johannes.Schindelin@gmx.de>,
	Brandon Casey <casey@nrlssc.navy.mil>,
	Jakub Narebski <jnareb@gmail.com>,
	Nicolas Pitre <nico@cam.org>, git@vger.kernel.org
To: Junio C Hamano <gitster@pobox.com>
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El 13/3/2008, a las 0:39, Junio C Hamano escribi=F3:

> Ah,...
>
> But C language rules haven't changed in such a way that it =20
> guarantees B to
> be evaluated before A when you write "A >=3D B", have it?
>
> So at least I think you would need something like this if you go that
> route:
>
>  		if (strcmp(value, "now")) {
>                	unsigned long now =3D approxidate("now");
>                	if (approxidate(value) >=3D now)
> 				return error("Invalid %s: '%s'", var, value);
> 			...
> 		}


Are you sure that that alternative provides any guarantees about =20
evaluation order either? (I'm not a compiler expert, nor am I =20
consulting a copy of the standard; but I don't think it does.)

In order to enforce evaluation in the required order I think it might =20
have to be something like this:

	if (strcmp(value, "now")) {
		unsigned long now;
		if ((now =3D approxidate("now")) &&
		    approxidate(value) >=3D now)
			return error("Invalid %s: '%s'", var, value);
		...
	}

ie. the && operator guarantees left to right evaluation order, and =20
since approxidate always returns a non-zero ulong the second =20
expression (after the &&) will always be evaluated.

Cheers,
Wincent