Path: utzoo!attcan!uunet!snorkelwacker!apple!agate!darkstar!terra!daniel
From: daniel@terra.ucsc.edu (Daniel Edelson)
Newsgroups: comp.lang.c++
Subject: Re: Can you prototype main()  ?????
Message-ID: <6932@darkstar.ucsc.edu>
Date: 16 Sep 90 23:04:18 GMT
References: <14227.26dc5b2f@max.u.washington.edu> <24447@uflorida.cis.ufl.EDU> 
    <59517@bbn.BBN.COM>
Sender: usenet@darkstar.ucsc.edu
Reply-To: daniel@cis.ucsc.edu (Daniel Edelson)
Organization: University of California, Santa Cruz
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In article <59517@bbn.BBN.COM> saustin@bbn.com (Steve Austin) writes:
>bp@swamp.cis.ufl.edu (Brian Pane) writes:
>
>>|> I tried to compile one of his example programs with Turbo C++ I got a
>>|> "cannot overload 'main'" error message.  It seems the compiler choked on
>>|> the author prototyping main (with the line:  int main();

>>Actually, main is "int main (int, char**)."  ....

From the 2.1 reference manual, section 3.4:

    ``The function main() may be defined as:
        int main() { /* ... */ }
    or
        int main(int argc, char * argv[]) { /* ... */ }''

From these two possible definitions it follows that main may have
either or two prototypes:
        int main();
    or
        int main(int argc, char * argv[]);
    
Of course, if you prototyped main() to have no arguments and then
defined it with two you must get an error. In C++ if your prototype
and definition differ in a way that is significant to the overloading
mechanism then you are declaring an overloaded function. (There may be
exceptions to this rule, I'm probably just over-generalizing.)

>>                                             If you declare main without
>>argc or argv, the compiler realizes that you must be talking about some
>>*other* main.  Perhaps the author was using a machine without an operating
>>system? :-)

You can certainly define main as ``int main() { /* ... */ }''
regardless of the operating system you're using. You simply
can't access the invocation arguments.

>I don't think it make much sense at all to prototype main. You prototype a
>function in order to call it - I don't know what you would get if you tried to
>call main, 

Again from section 3.4, ``The function main() may not be called from within a 
program.''

>           but I bet it wouldn't be good. Also, if you do manage to prototye
>main, you will be asking for its name to be mangled, which will not please 
>your linker.

Not a problem. The compiler (to be useful) must be able to
set the program's entry point.

>Other things wrong with the above definition "int main(int, char **)" are that
>main does not return a value (again, I'm not sure what would happen if you
>tried to return someting from main, but I bet it wouldn't be very meaningful).

Again, from section 3.4, ``A return statement in main() has the effect
of calling exit() with the return value as the argument.''

>Also, main can have a third argument (at least on some systems) which is a
>"char **" and conatins the environment.

This is nonstandard, though prevalent. According to ANSI C
freestanding systems need not support the environment.

>    Steve Austin

Daniel Edelson                   |  C++ virtual garbage recycler:
daniel@cis.ucsc.edu, or          |    ``Recycle your garbage. Please
 ....!sun!practic!peren!daniel    |    don't make me clean up after you.''