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From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.lang.c
Subject: Re: Type checking in conditional expressions
Message-ID: <31175@sun.uucp>
Date: Sun, 18-Oct-87 21:24:21 EDT
Article-I.D.: sun.31175
Posted: Sun Oct 18 21:24:21 1987
Date-Received: Mon, 19-Oct-87 02:09:24 EDT
References: <186@wright.EDU>
Sender: news@sun.uucp
Lines: 38
Keywords: HELP!

> 	Here's what I'm doing. C compilers don't check the types
> or number of parameters in function calls where the function is 
> external to the file being compiled. This has caused me lots of problems
> since I'm forgetful and often goof up the actual parameter list for
> my function calls. To provide this checking I created some macros of the
> form...

If you're working on a UNIX system, use "lint".  If you're working on a
non-UNIX system that has "lint" (I think there are, for example, "lint"s for
the PC out there), use "lint".  This does this sort of checking for you,
*without* having to cook up that sort of macro or waste data space, etc. with
dummy variables.  It will also check for a lot of *other* problems, especially
if you use the "-h" flag (or, in the case of later "lint"s, if you *don't* use
the "-h" flag - the default for many of these useful tests was changed from
"don't" to "do").

> 	After consulting K&R about the conditional operator, I tried
> some simple test cases like
> 	main()
> 		{ void function();
> 		  void (*name)();
> 		  name = function;
> 		  name = (0?name:function);
> 		}
> I figured if name and function were truly incompatible, the first 
> assignment should fail to compile, but it didn't. At the same time, 
> the compiler complained about the conditional expression in the last line.
> 
> 	Could someone please explain to me what's going on here?

Yes.  What's happening here is that you're tickling a bug in the compiler.
"name" and "function" are *not* incompatible; the compiler is just confused.
This sounds like a PCC bug, which makes me suspect you're using UNIX, in which
case you should use "lint" instead of that macro trick.  (This bug is fixed in
4.3BSD.)
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guytant,tant,tlif