linux-kernel - Re: detecting integer constant expressions in macros

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Message-ID: <CA+55aFw0YtFYEVA7YJHfvfKFqt+sph2swDmMmf9A4A2N7xtJEA@mail.gmail.com>
Date:   Tue, 20 Mar 2018 16:09:51 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Uecker, Martin" <Martin.Uecker@....uni-goettingen.de>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: detecting integer constant expressions in macros

On Tue, Mar 20, 2018 at 4:07 PM, Uecker, Martin
<Martin.Uecker@....uni-goettingen.de> wrote:
>
> talking of crazy ideas, here is another way to preserve
> integer const expressions in macros by storing it a
> VLA type (only for positive integers I guess):
>
>
> #define MAX(a, b) sizeof(*({    \
>         typedef char _Ta[a];    \
>         typedef char _Tb[b];    \
>         (char(*)[sizeof(_Ta) > sizeof(_Tb) ? sizeof(_Ta) :
> sizeof(_Tb)])0; }))

I liked your previous hack more. This is much more limited and not
nearly as disgustingly subtle.

              Linus