From owner-freebsd-questions Wed Jan 12 18:35:28 2000 Delivered-To: freebsd-questions@freebsd.org Received: from dorifer.heim3.tu-clausthal.de (dorifer.heim3.tu-clausthal.de [139.174.243.252]) by hub.freebsd.org (Postfix) with ESMTP id BFDFC14A26 for ; Wed, 12 Jan 2000 18:35:20 -0800 (PST) (envelope-from olli@dorifer.heim3.tu-clausthal.de) Received: (from olli@localhost) by dorifer.heim3.tu-clausthal.de (8.9.3/8.9.3) id DAA64583; Thu, 13 Jan 2000 03:34:34 +0100 (CET) (envelope-from olli) Date: Thu, 13 Jan 2000 03:34:34 +0100 (CET) Message-Id: <200001130234.DAA64583@dorifer.heim3.tu-clausthal.de> From: Oliver Fromme To: freebsd-questions@FreeBSD.ORG Reply-To: freebsd-questions@FreeBSD.ORG Subject: Re: Giving a sighandler more information X-Newsgroups: list.freebsd-questions In-Reply-To: <85jcfs$1oj0$1@atlantis.rz.tu-clausthal.de> User-Agent: tin/1.4.1-19991201 ("Polish") (UNIX) (FreeBSD/3.4-19991219-STABLE (i386)) MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Sender: owner-freebsd-questions@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.ORG Laurence Berland wrote in list.freebsd-questions: > Followup question: is a sig_atomic_t appropriate to hold the value of a > FILE * ? No. It is only guaranteed to be large enough to hold an int. Of course, on intel PCs, a pointer has the same size as an int, but not on other platforms (e.g. the Alpha). Therefore, portable programs cannot store a pointer in a sig_atomic_t. Apart from that: You can't use a FILE* within a signal handler anyway, because most of stdio's functions are not guaranteed to be re-entrant. If you have to do something with a file within a signal handler, use the lower-level file handling functions based on file descriptors, i.e. open(), read(), write(), close(). Conveniently, a file descriptor fits in a sig_atomic_t, too. Please refer to the sigaction(2) manpage, it contains a complete list of all functions that are "async-signal safe". All other functions are _not_ safe to use from within a signal handler. Regards Oliver -- Oliver Fromme, Leibnizstr. 18/61, 38678 Clausthal, Germany (Info: finger userinfo:olli@dorifer.heim3.tu-clausthal.de) "In jedem Stück Kohle wartet ein Diamant auf seine Geburt" (Terry Pratchett) To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message