From: Andrew Morton <akpm@osdl.org>
To: Randy Dunlap <randy.dunlap@oracle.com>
Cc: linux-mm@kvack.org
Subject: Re: [PATCH] typeof __page_to_pfn with SPARSEMEM=y
Date: Fri, 26 Jan 2007 12:34:32 -0800 [thread overview]
Message-ID: <20070126123432.93a175f2.akpm@osdl.org> (raw)
In-Reply-To: <20070126120113.c17c1174.randy.dunlap@oracle.com>
On Fri, 26 Jan 2007 12:01:13 -0800
Randy Dunlap <randy.dunlap@oracle.com> wrote:
> From: Randy Dunlap <randy.dunlap@oracle.com>
>
> With CONFIG_SPARSEMEM=y:
>
> mm/rmap.c:579: warning: format '%lx' expects type 'long unsigned int', but argument 2 has type 'int'
>
> Make __page_to_pfn() return unsigned long.
>
> Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
> ---
> include/asm-generic/memory_model.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- linux-2620-rc6.orig/include/asm-generic/memory_model.h
> +++ linux-2620-rc6/include/asm-generic/memory_model.h
> @@ -54,7 +54,7 @@
> #define __page_to_pfn(pg) \
> ({ struct page *__pg = (pg); \
> int __sec = page_to_section(__pg); \
> - __pg - __section_mem_map_addr(__nr_to_section(__sec)); \
> + (unsigned long)(__pg - __section_mem_map_addr(__nr_to_section(__sec))); \
> })
whaa? The difference between two pointers has type `int' on a 64-bit
compiler. How stupid.
<reads the book>
A.4 Important Data Types
========================
The result of subtracting two pointers in C is always an integer, but
the precise data type varies from C compiler to C compiler. Likewise,
the data type of the result of `sizeof' also varies between compilers.
ISO defines standard aliases for these two types, so you can refer to
them in a portable fashion. They are defined in the header file
`stddef.h'.
-- Data Type: ptrdiff_t
This is the signed integer type of the result of subtracting two
pointers. For example, with the declaration `char *p1, *p2;', the
expression `p2 - p1' is of type `ptrdiff_t'. This will probably
be one of the standard signed integer types (`short int', `int' or
`long int'), but might be a nonstandard type that exists only for
this purpose.
So it seems that's `int' on (at least) x86_64.
How the hell can that be reliable? I'm missing something here...
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prev parent reply other threads:[~2007-01-26 20:34 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-01-26 20:01 [PATCH] typeof __page_to_pfn with SPARSEMEM=y Randy Dunlap, Randy Dunlap
2007-01-26 20:34 ` Andrew Morton [this message]
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