linux-kernel - Re: X32 psABI status update

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Message-ID: <AANLkTikYxVzFjLQFNvEy2FBmuO76PJPA5JuLgoUGzPF0@mail.gmail.com>
Date:	Mon, 21 Mar 2011 03:52:04 -0700
From:	"H.J. Lu" <hjl.tools@...il.com>
To:	Michael Matz <matz@...e.de>
Cc:	Mike Frysinger <vapier@...too.org>, libc-alpha@...rceware.org,
	GCC Development <gcc@....gnu.org>,
	LKML <linux-kernel@...r.kernel.org>, x32-abi@...glegroups.com
Subject: Re: X32 psABI status update

On Mon, Mar 21, 2011 at 1:20 AM, Michael Matz <matz@...e.de> wrote:
> Hi,
>
> On Sun, 20 Mar 2011, H.J. Lu wrote:
>
>> I don't think it will help x32 and I think it will make it harder to add
>> x32 support. I still want to see a real usage before I add it.
>
> % cat real-world.c
> /* intptr_t; what's that? */
> union space_saving_htab_element {
>  void *generic_pointer;
>  /* Usually we need a long for a pointer, but I just figured out
>     that on x32 an int is enough and smaller.  My program
>     now needs half as much memory, supi!  */
> #ifdef __x32__
>  unsigned int as_number;
> #else
>  unsigned long as_number;
> #endif
> };

That is the wrong way to support x32.  You should remove "#ifdef __x32__",
which only shows __x32__ shouldn't be used/needed.

>
> Ciao,
> Michael.
> PS: Of course you and I wouldn't write such code, but Mikes point was that
> there might be some that do.  I could probably construct an example where
> it would matter for real involving inline asm that for some reason has to
> slightly differ depending on x32-ness.
>

I  am still waiting for a real example.

-- 
H.J.
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