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Message-ID: <20141123193902.GN29621@brightrain.aerifal.cx>
Date: Sun, 23 Nov 2014 14:39:02 -0500
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: [PATCH] Add stdatomic.h for clang>=3.1 and gcc>=4.1
On Sun, Nov 23, 2014 at 07:01:24PM +0100, Jens Gustedt wrote:
> Am Sonntag, den 23.11.2014, 11:37 -0500 schrieb Rich Felker:
> > But it's a variably-modified type, so sizeof and typeof evaluate the
> > expression when their operand is of this type. Thus, all you have
> > to do is make an array of objects of this type, and then refer to
> > arr[i++]. This will be an expression with variably-modified type,
>
> yes, but not a VLA
>
> > and the evaluation will have unwanted side effects.
>
> No, I don't think it is evaluated, 6.5.3.4 says:
>
> If the type of the operand is a variable length array type, the
> operand is evaluated;
>
> observe that it says VLA, and not VM type.
>
> otherwise, the operand is not evaluated and the result is an integer
> constant.
>
> There are no exception for other VM types. To deduce the size for our
> case here, an evaluation isn't necessary.
>
> (Hoping that the __typeof__ stuff follows the same rules.)
OK, thanks for clarifying this. In that case I think we're safe as
long as __typeof__ follows the same rules.
Rich
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