misc/144749: [libstand] [patch] make assert.c use abort(3) instead of exit(3)

[Bruce Evans]

The following reply was made to PR kern/144749; it has been noted by GNATS.

From: Bruce Evans <brde at optusnet.com.au>
To: Alexander Best <alexbestms at wwu.de>
Cc: freebsd-gnats-submit at FreeBSD.org, freebsd-bugs at FreeBSD.org
Subject: Re: misc/144749: [libstand] [patch] make assert.c use abort(3)
 instead of exit(3)
Date: Tue, 16 Mar 2010 02:06:55 +1100 (EST)

 On Sun, 14 Mar 2010, Alexander Best wrote:
 
 >> Description:
 > gcc complaints about the use of exit() in assert.c:
 >
 > /usr/src/lib/libstand/assert.c:43: warning: implicit declaration of function
 > 'exit'
 
 It's not clear where this should be declared, or even it must exist.
 exit() might be supplied by the application, but if not then it doesn't
 exist and it is invalid for assert() to call it.  libstand(3) of course
 doesn't document either exit() or the need to supply it to support
 assert().
 
 > the attached patch replaces exit() (which is used illegally anyway, because no integer argument is being supplied) with abort().
 
 The use might be legal, since libstand is freestanding so its exit might be
 unrelated to the Standard C exit.  However, most or all implementations of 
 exit() in /sys/boot take an arg.
 
 > assert.c uses stand.h which conflicts with stdlib.h. so this patch also defines abort() in stand.h being an external function.
 
 abort() certainly is not required to exist, and in fact doesn't exist for
 any application in /sys/boot, so this change would mainly break most boot
 code at link time.
 
 libstand is independent of libc, so it is a bug for anything in it or
 any application that uses it to include <stdlib.h>.  In libstand and
 /sys/boot, this bug seems to be present only in ficl (the include is
 ifdefed in only some places in ficl but in all places in libstand).
 
 A nearby function that doesn't exist is atexit().  This is only
 called from ifdefed out code in zalloc_malloc.c.
 
 >
 > cheers.
 > alex
 >> How-To-Repeat:
 > cd /usr/src/lib/libstand && make
 >> Fix:
 >
 >
 > Patch attached with submission follows:
 >
 > Index: lib/libstand/assert.c
 > ===================================================================
 > --- lib/libstand/assert.c	(revision 205121)
 > +++ lib/libstand/assert.c	(working copy)
 > @@ -40,5 +40,5 @@
 > 	else
 > 		printf("Assertion failed: (%s), function %s, file %s, line "
 > 		    "%d.\n", expression, func, file, line);
 
 It would be nice to fix the style bug in this (use of C90 string
 concatenation to obfuscate the message).  This style bug os missing in
 the libc version.
 
 > -	exit();
 > +	abort();
 > }
 > Index: lib/libstand/stand.h
 > ===================================================================
 > --- lib/libstand/stand.h	(revision 205121)
 > +++ lib/libstand/stand.h	(working copy)
 > @@ -265,6 +265,7 @@
 > extern char	*optarg;			/* getopt(3) external variables */
 > extern int	optind, opterr, optopt, optreset;
 > extern int	getopt(int, char * const [], const char *);
 > +extern void	abort(void);
 
 Further unsorting of the declarations.
 
 Note that exit() is of a different nature than getopt() -- it is
 supplied by the application (if it exists), while getopt() is supplied
 by libstand.  So there should be a separate section to declare exit() and
 any other function that must be supplied by the application.
 
 >
 > /* pager.c */
 > extern void	pager_open(void);
 
 ISTR that there were once similar problems declaring main().  When it
 wasn't declared explicitly, gcc -Wmumble used to warn about this.  So
 someone "fixed" this by declaring it in a standard header.  But it
 cannot be declared in a standard header since it has more than one
 valid parameter list ((void), and the usual (argc, argv), and maybe
 more).
 
 Bruce