Re: [PATCH] uapi: fix asm/signal.h userspace compilation errors

From: "Dmitry V. Levin" <ldv@altlinux.org>
To: "Carlos O'Donell" <carlos@systemhalted.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
	Russell King <linux@armlinux.org.uk>,
	Haavard Skinnemoen <hskinnemoen@gmail.com>,
	Hans-Christian Egtvedt <egtvedt@samfundet.no>,
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	Jesper Nilsson <jesper.nilsson@axis.com>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Tony Luck <tony.luck@intel.com>,
	Fenghua Yu <fenghua.yu@intel.com>,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Ralf Baechle <ralf@linux-mips.org>,
	David Howells <dhowells@redhat.com>,
	"James E.J. Bottomley" <jejb@parisc-linux.org>,
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	Paul Mackerras <paulus@samba.org>,
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Subject: Re: [PATCH] uapi: fix asm/signal.h userspace compilation errors
Date: Thu, 2 Mar 2017 18:48:45 +0300	[thread overview]
Message-ID: <20170302154845.GB3503@altlinux.org> (raw)
In-Reply-To: <CAE2sS1h9QNV+31GMSv8aahJYOb9hFtFp5Aj-yVOfg7cjBHr_kg@mail.gmail.com>

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On Thu, Mar 02, 2017 at 10:22:18AM -0500, Carlos O'Donell wrote:
> On Wed, Mar 1, 2017 at 11:20 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> > On Sun, Feb 26, 2017 at 2:01 AM, Dmitry V. Levin <ldv@altlinux.org> wrote:
> >> Include <stddef.h> (guarded by #ifndef __KERNEL__) to fix asm/signal.h
> >> userspace compilation errors like this:
> >>
> >> /usr/include/asm/signal.h:126:2: error: unknown type name 'size_t'
> >>   size_t ss_size;
> >>
> >> As no uapi header provides a definition of size_t, inclusion
> >> of <stddef.h> seems to be the most conservative fix available.
[...]
> > I'm not sure if this is the best fix. We generally should not include one
> > standard header from another standard header. Would it be possible
> > to use __kernel_size_t instead of size_t?
> 
> In glibc we handle this with special use of __need_size_t with GCC's
> provided stddef.h.
> 
> For example glibc's signal.h does this:
> 
> # define __need_size_t
> # include <stddef.h>

Just to make it clear, do you suggest this approach for asm/signal.h as well?

[...]
> Changing the fundamental type causes the issues you see in patch v2
> where sizeof(size_t) < sizeof(__kernel_size_t).
> 
> It will only lead to problem substituting the wrong type.

I don't see any appetite for creating more ABIs like x32 with
sizeof(size_t) < sizeof(__kernel_size_t), so v2 approach
is not going to be any different from v1 in maintenance.

-- 
ldv

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