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Re: [PATCH v2 2/4] linux/const.h: move UL() macro to include/linux/const.h

From David Howells <dhowells@redhat.com>
Newsgroups linux.kernel
Subject Re: [PATCH v2 2/4] linux/const.h: move UL() macro to include/linux/const.h
Date 2017-01-06 11:50 +0100
Message-ID <sWAfT-w2-1@gated-at.bofh.it> (permalink)
References <sW5Yu-4QA-5@gated-at.bofh.it> <sW5Yu-4QA-7@gated-at.bofh.it> <sW5Yu-4QA-5@gated-at.bofh.it>
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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

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Thread

[PATCH v2 2/4] linux/const.h: move UL() macro to include/linux/const.h Masahiro Yamada <yamada.masahiro@socionext.com> - 2017-01-05 03:30 +0100
  Re: [PATCH v2 2/4] linux/const.h: move UL() macro to  include/linux/const.h Catalin Marinas <catalin.marinas@arm.com> - 2017-01-05 12:20 +0100
  Re: [PATCH v2 2/4] linux/const.h: move UL() macro to  include/linux/const.h Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-01-05 12:40 +0100
  Re: [PATCH v2 2/4] linux/const.h: move UL() macro to include/linux/const.h David Howells <dhowells@redhat.com> - 2017-01-06 11:50 +0100
    Re: [PATCH v2 2/4] linux/const.h: move UL() macro to include/linux/const.h Masahiro Yamada <yamada.masahiro@socionext.com> - 2017-01-08 07:30 +0100

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