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From: David Howells <dhowells@redhat.com>
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To: Masahiro Yamada <yamada.masahiro@socionext.com>
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Subject: Re: [PATCH v2 2/4] linux/const.h: move UL() macro to include/linux/const.h
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Date: Fri, 06 Jan 2017 10:45:55 +0000
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Masahiro Yamada <yamada.masahiro@socionext.com> wrote:

> diff --git a/include/uapi/linux/const.h b/include/uapi/linux/const.h
> index c872bfd..76fb0f9 100644
> --- a/include/uapi/linux/const.h
> +++ b/include/uapi/linux/const.h
> @@ -1,7 +1,7 @@
>  /* const.h: Macros for dealing with constants.  */
>  
> -#ifndef _LINUX_CONST_H
> -#define _LINUX_CONST_H
> +#ifndef _UAPI_LINUX_CONST_H
> +#define _UAPI_LINUX_CONST_H

You need to be very careful doing this.  Some userspace stuff depends on the
guard macro names on the kernel header files.

>  /* Some constant macros are used in both assembler and
>   * C code.  Therefore we cannot annotate them always with
> @@ -21,7 +21,10 @@
>  #define _AT(T,X)	((T)(X))
>  #endif
>  
> +#define _UL(x)		(_AC(x, UL))
> +#define _ULL(x)		(_AC(x, ULL))

How likely is this to collide with existing userspace code somewhere?  It
looks like the sort of thing that could collide with a C library.

David