NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part1/8260

Text File | 1996-08-05 | 2.1 KB | 56 lines

Path: mail2news.demon.co.uk!genesis.demon.co.uk
From: Lawrence Kirby <[e-mail]>
Newsgroups: comp.lang.c
Subject: Re: Type casting
Date: Sat, 02 Mar 96 14:40:32 GMT
Organization: none
Message-ID: <[e-mail]>
References: <4gfnmi$[e-mail]> <4h5amm$[e-mail]> <[e-mail]>
Reply-To: [e-mail]
X-NNTP-Posting-Host: genesis.demon.co.uk
X-Newsreader: Demon Internet Simple News v1.27
X-Mail2News-Path: genesis.demon.co.uk

In article <[e-mail]>
           [e-mail] "Kazimir Kylheku" writes:

>Incidentally, the only specific reference to undefined behavior in the context
>of main() that I have been able to dig up in the Standard says that the exit
>status of a program which doesn't provide a return value on exit from main() is
>undefined. There is no discussion over T main() where T is not int, versus int
>main().

5.1.2.2.1 describes the behaviour of main when it is defined as

    int main(void)   { /*...*/ }

or

    int main(int argc, char *argv[]) { /*...*/ }

Some other forms can be shown to have the same behaviour as these from the
rest of the standard (e.g. int main() or int main(int argc, char **argv) )
but all of these forms return int. Nowhere does the standard define any
behaviour for main returning a type other than int (or indeed most function
declarations that do return int).

3.16 undefined behaviour

"...

 If a ``shall'' or ``shall not'' requirement that appears outside of a
 constraint is violated, the behaviour is undefined. Undefined behaviour
 is otherwise indicated in this International Standard by the words
 ``undefined behaviour'' ## or by the omission of any explicit definition
 of behaviour. There is no difference in emphasis among these three; they
 all describe ``behaviour that is undefined.''"

Note particularly everything after my ## mark. So void main() quite
specifically invokes undefined behaviour according to the standard.

--
-----------------------------------------
Lawrence Kirby | [e-mail]
Wilts, England | [e-mail]
-----------------------------------------