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From: Arnd Bergmann <arnd@arndb.de>
Date: Wed, 1 Mar 2017 17:20:50 +0100
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Subject: Re: [PATCH] uapi: fix asm/signal.h userspace compilation errors
To: "Dmitry V. Levin" <ldv@altlinux.org>
Cc: Russell King <linux@armlinux.org.uk>,
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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.
>
> On the kernel side size_t is typedef'ed to __kernel_size_t, so
> an alternative fix would be to change the type of sigaltstack.ss_size
> from size_t to __kernel_size_t for all architectures except those where
> sizeof(size_t) < sizeof(__kernel_size_t), namely, x32 and mips n32.
>
> On x32 and mips n32, however, #include <stddef.h> seems to be the most
> straightforward way to obtain the definition for sigaltstack.ss_size's
> type.
>
> Signed-off-by: Dmitry V. Levin <ldv@altlinux.org>

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?

     Arnd