Date: Thu, 20 Jan 2000 08:27:18 +1100 (EST) From: Bruce Evans <bde@zeta.org.au> To: Garrett Wollman <wollman@khavrinen.lcs.mit.edu> Cc: Satoshi Asami <asami@cs.berkeley.edu>, current@FreeBSD.ORG Subject: Re: sigisempty? Message-ID: <Pine.BSF.4.21.0001200800100.1541-100000@alphplex.bde.org> In-Reply-To: <200001191657.LAA29895@khavrinen.lcs.mit.edu>
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On Wed, 19 Jan 2000, Garrett Wollman wrote: > <<On Wed, 19 Jan 2000 07:03:04 -0800 (PST), asami@cs.berkeley.edu (Satoshi Asami) said: > > > How do I test if sigset_t is empty in -current? The xview sources > > have this macro: > > int > sigisempty(sigset_t *my_sigset) > { > static sigset_t empty_ss; > static int emptied; > > if (!emptied) { > sigemptyset(&empty_ss); > emptied++; > } > > return (memcmp(my_sigset, &empty_ss, sizeof empty_ss) == 0); > } You should know better than to compare structs for equality. Even the implementation can't do this in a machine-independent way. The current implementation can do it machine-independently by comparing each element of the __bits[] struct member with 0. The correct answer seems to be "you can't do that" :-). Even checking all signals from 1 to the maximum signal number is difficult because the maximum signal number is difficult to determine and it may be INT_MAX. rcs has fought with variations of this problem. It now uses the following method: keep track of the largest signal number of interest for the current operation, and check all signals from that signal number down to 1. See rcs/lib/rcsutil.c. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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