From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Fri, 26 Jan 2007 12:34:32 -0800 From: Andrew Morton Subject: Re: [PATCH] typeof __page_to_pfn with SPARSEMEM=y Message-Id: <20070126123432.93a175f2.akpm@osdl.org> In-Reply-To: <20070126120113.c17c1174.randy.dunlap@oracle.com> References: <20070126120113.c17c1174.randy.dunlap@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Randy Dunlap Cc: linux-mm@kvack.org List-ID: On Fri, 26 Jan 2007 12:01:13 -0800 Randy Dunlap wrote: > From: Randy Dunlap > > 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 > --- > 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. 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... -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org