From mboxrd@z Thu Jan  1 00:00:00 1970
From: Mike Haertel <mike@ducky.net>
Message-Id: <200104261917.f3QJHlG03409@ducky.net>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] the declaration of main()
In-Reply-To: <20010426182650.3DDB3199D7@mail.cse.psu.edu>
Date: Thu, 26 Apr 2001 12:17:47 -0700
Topicbox-Message-UUID: 922cdc6a-eac9-11e9-9e20-41e7f4b1d025

Forsyth wrote:

>cpu% cat s4/crt0.s
>/ C runtime startoff

Note that Forsyth's example is from 6th edition Unix, not 7th edition.
(The "s4/" in the source file name is a dead giveaway.)

Here's the corresponding code fragment from 7th edition
/usr/src/libc/csu/crt0.s:

1:
	mov	r0,4(sp)
	mov	r0,_environ
	jsr	pc,_main
	cmp	(sp)+,(sp)+
	mov	r0,(sp)
	jsr	pc,*$_exit
	sys	exit

Here the int return value from main does indeed become the exit status.

C didn't really become widely used until after the 7th edition, and
v7 C is really the ancestral root of most other implementations.  It is
also the version of the language that most nearly coincided with the
publication of the 1st edition of "The C Programming Language".