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From: Anton A. <ai...@ca...> - 2004-02-28 09:57:28
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On Feb 28 2004, Andras Erdei wrote: > the reason you felt you need the circles is that sometimes > a.h needs an incomplete type from b.h and at the same time > b.h really depends on a.h >=20 > this is why runlist.h forward declares runlist_element and > runlist before including attrib.h: attrib.h needs incomplete > types from runlist.h, and runlist.h depends on attrib.h; but > you still had to handcode that into runlist.h because circular > includes don't really solve this problem (1 & 2 means they > don't do anything at all when they compile) Correct. =20 > volume.h similarly forward declares ntfs_volume before including > other headers; i haven't got further yet :O) >=20 > using handcoded forward declarations is one option, but afaik > the canonical (pretty) solution is to provide separate forward > declaration headers, like >=20 > runlist_fwd.h: > typedef struct _runlist_element runlist_element; > typedef runlist_element runlist; >=20 > attrib.h: > #include "runlist_fwd.h"=09<-- instead of "runlist.h" > ... >=20 > handcoding the forward declarations into the header > is perfectly o.k. (although the right place is attrib.h, > not runlist.h), but having a forwarding header means I don't want to forward declare runlist stuff in attrib.h. Bound to cause= =20 headaches later on when somethin in runlist.h gets modified and we have to= =20 hunt all the other forward declarations. This is why the includes are=20 circular and use header guards. > - slightly less maintenance (only one file has to be > edited when e.g. you add a new type to runlist.h) >=20 > - slightly faster compilation (user code that only > needs the incomplete type can also include the _fwd.h > instead of the real one) >=20 > - imho a bit more clarity I agree. Would you like to send me patches doing the _fwd.h thing? Best regards, Anton --=20 Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @) Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK Linux NTFS maintainer / IRC: #ntfs on irc.freenode.net WWW: http://linux-ntfs.sf.net/ & http://www-stu.christs.cam.ac.uk/~aia21/ |
