Messages in this thread |  | | | Date | Wed, 24 Jul 2002 09:24:02 +0100 | | From | Anton Altaparmakov <> | | Subject | Re: type safe lists (was Re: PATCH: type safe(r) list_entry repacement: generic_out_cast) |
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At 08:39 24/07/02, Martin Brulisauer wrote: >On 24 Jul 2002, at 2:07, Joshua MacDonald wrote: >I have one additional comment to the current implementation: > > > > #define TS_LINK_TO_ITEM(ITEM_TYPE,LINK_NAME,LINK) \ > > ((ITEM_TYPE *)((char *)(LINK)-(unsigned long)(&((ITEM_TYPE > *)0)->LINK_NAME))) > >As long as your pointers are 32bit this seems to be ok. But on >64bit implementations pointers are not (unsigned long) so this cast >seems to be wrong.
On 64-bit architectures unsigned long is 64-bits so there is no problem. In fact the core kernel code _requires_ that unsigned long is large enough to fully contain the contents of a pointer. (E.g. look at linux/mm/memory.c, well really linux/mm/*.c for the tip of the iceberg). Of course if one wanted to be really pedantic, one could replace the unsigned long typecasts with ptrdiff_t. But you would have to go through a _lot_ of code where the kernel currently casts between unsigned long and (mostly) void * to do this in a one off conversion.
Best regards,
Anton
-- "I've not lost my mind. It's backed up on tape somewhere." - Unknown -- Anton Altaparmakov <aia21 at cantab.net> (replace at with @) Linux NTFS Maintainer / IRC: #ntfs on irc.openprojects.net WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/
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