Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uunet!hoptoad!tim
From: tim@hoptoad.uucp (Tim Maroney)
Newsgroups: comp.sys.mac.programmer
Subject: Re: More on MPW C 3.0 question
Message-ID: <10311@hoptoad.uucp>
Date: 19 Feb 90 07:48:46 GMT
References: <162.25dfe4b3@waikato.ac.nz>
Reply-To: tim@hoptoad.UUCP (Tim Maroney)
Organization: Eclectic Software, San Francisco
Lines: 52

In article <162.25dfe4b3@waikato.ac.nz> ccc_ldo@waikato.ac.nz writes:
>While porting a large C program between versions of MPW C, I came
>across a strange quirk in the 3.0 compiler, which is summed up in
>the following program:
>
>	typedef unsigned char Str255[256];

Uh, why not use MPW's own definition of Str255?  It's identical to the
above in effect, so I'm just curious.

>	main()
>	  {
>	    Str255
>		temps, *tempp;

"Str255 *tempp" makes no sense.  You can't have a pointer to an array
in C.  The compiler should choke on this, but it doesn't.  Instead,
your declarations should go:

	Str255 temps;
	StringPtr tempp;

>	    tempp = &temps;
>
>When I try to compile this, the compiler throws up the following
>error message:
>
>	#    tempp = &temps;
>	#                  ?
>	### Error 225 Incompatible types for assignment

Yep.  It's trrying to assign to a nonsensical type, so it's not too
surprising that it barfs.  However, if you declare as above and say:

	tempp = temps;

everything should be hunky dory.

I've noticed that MPW allows these nonsensical types myself; at one
point, I think in GetPattern or GetIndPattern, a parameter is defined
as a "Pattern *", which makes no sense since Pattern is just an array
of eight characters.  Nor will it let you generate an lvalue of this
nonsensical type by putting the address operator (&) in front of the
name of a variable of type Pattern.  The only thing you can do to make
it work is a type cast to (Pattern *).  Sounds pretty much the same as
your problem.  I think the compiler should disallow these silly
declarations in the first place, but if not, it should let you generate
pointers to arrays with the address operator.
-- 
Tim Maroney, Mac Software Consultant, sun!hoptoad!tim, tim@toad.com

This message does represent the views of Eclectic Software.