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Date: Mon, 9 Oct 2006 14:20:26 +0200 (MEST) From: Jan Engelhardt <jengelh@...ux01.gwdg.de> To: Kyle Moffett <mrmacman_g4@....com> cc: David Howells <dhowells@...hat.com>, Matthew Wilcox <matthew@....cx>, torvalds@...l.org, akpm@...l.org, sfr@...b.auug.org.au, linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org Subject: Re: [PATCH 1/4] LOG2: Implement a general integer log2 facility in the kernel [try #4] >> > > > Were you planning on porting Linux to a machine with >> > > > non-8-bit-bytes any >> > > > time soon? Because there's a lot more to fix than this. >> > > >> > > I am considering the case [assuming 8-bit-byte machines] where >> > > sizeof(u32) is not 4. Though I suppose GCC will probably make a >> > > 32-bit >> > > type up if the hardware does not know one. >> > >> > If the machine has 8-bit bytes, how can sizeof(u32) be anything other >> > than 4? >> >> typedef unsigned int u32; >> >> Though this should not be seen in the linux kernel. > > Well, uhh, actually... > > All presently-supported architectures do exactly that. Well, some do: > > typedef unsigned int __u32; > #ifdef __KERNEL__ > typedef __u32 u32; > #endif Ouch ouch ouch. It should better be typedef uint32_t __u32; So that even if there happens to be a compiler that does sizeof(int)=8, sizeof(u32) will actually be 4. Say, if there happens to be an architecture that does only know 64-bit integers, the compiler will have some extra magic to make uint32_t behave like a 32-bit type in C and transparently use 64-bit assembler. So far the theory. -`J' -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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