Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uunet!mcsun!hp4nl!philapd!ssp11!dolf
From: dolf@idca.tds.PHILIPS.nl (Dolf Grunbauer)
Newsgroups: comp.lang.c
Subject: Re: Return value from a macro
Keywords: macro linked list
Message-ID: <634@ssp11.idca.tds.philips.nl>
Date: 1 Feb 90 09:46:03 GMT
References: <960@pyrite4.UUCP> <7727@pt.cs.cmu.edu>
Organization: Philips Telecommunication and Data Systems, The Netherlands
Lines: 23

In article <7727@pt.cs.cmu.edu> mwm@a.gp.cs.cmu.edu (Mark Maimone) writes:
]In article <960@pyrite4.UUCP> Larry Baltz writes:
]>The problem I'm having is trying to have the macro return a value of the 
]>deleted link.
]	You can just use the comma operator to return a value (the value of
]a comma-expression is the last item in the list).  Here's one solution:
]
]#define delete_head(head) ((header->next == header) ? NULL : \
]	(dh_temp = (head)->next, dh_temp->next->prev = (head), \
]	(head)->next = dh_temp->next, dh_temp))
]
]static LINK dh_temp;

Oke, but note that the solution of Mark doesn't work when the code is supposed
to be shared by other processes at the same time. E.g. in a kernel or a 
shared library there probably will only be one dh_temp for all processes
thus (due to scheduling cq process switching) it is likely that these processes
ruin the value of dh_temp, creating very hard to trace errors/bugs/panics.
-- 
Dolf Grunbauer          Tel: +31 55 433233  Internet dolf@idca.tds.philips.nl
Philips Telecommunication and Data Systems  UUCP ....!mcvax!philapd!dolf
Dept. SSP, P.O. Box 245, 7300 AE Apeldoorn, The Netherlands         n   n   n
It's a pity my .signature is too small to show you my solution of  a + b = c