Date: Wed, 12 Jan 2000 21:50:41 -0500 From: "Mikhail Evstiounin" <evstiounin@adelphia.net> To: <freebsd-questions@FreeBSD.ORG> Subject: Re: Giving a sighandler more information Message-ID: <00a201bf5d70$fb0cbea0$fc353018@evstiouninadelphia.net.pit.adelphia.net>
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-----Original Message----- From: Oliver Fromme <olli@dorifer.heim3.tu-clausthal.de> To: freebsd-questions@FreeBSD.ORG <freebsd-questions@FreeBSD.ORG> Date: Wednesday, January 12, 2000 9:37 PM Subject: Re: Giving a sighandler more information >Laurence Berland <stuyman@confusion.net> 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. Sorry, guys, but it requirenments of ANSI that sizeof(void*)==sizeof(int). Don't get me wrong, I like Alpha, but alpha compiler is not 100% ANSI compatible. If you take a look at HP aCC and 64 bit architecture - you will see the same. So, let me rephrase it - in ANSI world you could do it. and question does it mean that alpha integer is 32 bit, or pointer has more than 64? I used GNU C a couple of times there and everything was OK. Is it a special compiler? > >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 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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