Path: utzoo!mnetor!uunet!husc6!bloom-beacon!athena.mit.edu!wesommer
From: wesommer@athena.mit.edu (William Sommerfeld)
Newsgroups: comp.lang.c
Subject: Re: exit(main(argc,argv,env));
Message-ID: <2058@bloom-beacon.MIT.EDU>
Date: 18 Dec 87 17:12:29 GMT
References: <10875@brl-adm.ARPA> <1451@houdi.UUCP>
Sender: daemon@bloom-beacon.MIT.EDU
Reply-To: wesommer@athena.mit.edu (William Sommerfeld)
Followup-To: comp.unix.questions
Organization: Massachusetts Institute of Technology
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This really isn't a C question; it is a UNIX question.

> 
> I was looking through the file crt0.c in the GNU emacs source code and
> found the command
> 
> exit(main(argc,argv,env));
> 

First misconception: exit() is a _function_ in the C library.  It
happens to be different from other functions in that it never returns
control to its caller, but that's just a property of the
implementation; there isn't anything in the C compiler which
special-cases exit(), or abort(), or any of the other special
functions.  You don't have to pass it a constant integer.

On UNIX, crt0.c happens to be the module which sets up argv, argc, and
the environment and then calls main() with the appropriate arguments;
it is silently included into the load image by 'cc' when you use it to
link a program.  Needless to say, it is highly architecture- and OS-
dependant.

GNU emacs has its own version of crt0.c (with probably hundreds of
#ifdefs to account for all sorts of machine dependancies) because it
has to be able to dump out a core image of itself containing
pre-loaded emacs lisp, and then restart this core image later.

				- Bill