Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!seismo!ut-sally!husc6!hao!noao!mcdsun!fnf From: fnf@mcdsun.UUCP (Fred Fish) Newsgroups: comp.os.minix Subject: Re: Keeping exit(3) small but making it work for stdio -- atexit() Message-ID: <333@mcdsun.UUCP> Date: Tue, 7-Jul-87 17:57:29 EDT Article-I.D.: mcdsun.333 Posted: Tue Jul 7 17:57:29 1987 Date-Received: Sat, 11-Jul-87 03:03:20 EDT References: <3118@felix.UUCP> <2352@hoptoad.uucp> <3169@felix.UUCP> <2368@hoptoad.uucp> Reply-To: fnf@mcdsun.UUCP (Fred Fish) Organization: Motorola Microcomputer Division Lines: 61 In article <2368@hoptoad.uucp> gnu@hoptoad.uucp (John Gilmore) writes: >While Art's solution works, there is a cleaner solution than >requiring the programmer to call _exit if she doesn't use stdio. >Minix can remain small and still be fixed to work properly. > ... >This should be easy to implement; you make an array of 33 function Yes, I just recently put a very similar fix in our version of SVR3 here, and it was only about a 2 hour job, most of which was figuring out the correct place in stdio to trigger the cleanup from exit. The results were well worth the work, a null program "main(){}" went from over 14Kb linked to just 298 bytes. The original 14Kb was because crt0.o references exit(), which pulls in cleanup(), which pulls in ... One possible problem with the implementation John outlined: what if the user calls atexit() with his own functions before doing any stdio? I.E., if he calls: atexit(func1); atexit(func2); do some stdio stuff for the first time atexit(func3); The queue of functions will look like: func3 -> _cleanup -> func2 -> func1 which is dequeue'd and executed in the order func3() _cleanup() func2() func1() with possibly unintentional results. My solution was to not use the atexit() routine to register the cleanup function, just set a global pointer (_stdio_cleanup) in exit and insure that it got dereferenced *after* all the functions registered by atexit(). P.S. I put my pointer initialization as the first statement in flsbuf() in flsbuf.c: unsigned char c1; + extern VOID (*_stdio_cleanup)(); /* Found in exit() module */ + _stdio_cleanup = _cleanup; do { This may or may not be the theoretically correct place to put it, so if someone more knowledgeable about stdio wants to speak up... -Fred -- = Drug tests; just say *NO*! = Fred Fish Motorola Computer Division, 3013 S 52nd St, Tempe, Az 85282 USA = seismo!noao!mcdsun!fnf (602) 438-5976