Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!pacific.mps.ohio-state.edu!linac!att!att!ima!dirtydog!karl
From: karl@ima.isc.com (Karl Heuer)
Newsgroups: comp.lang.c
Subject: Re: Why have xxx_t typedef names (was Re: Is typedef char BUFFER[20] legal?)
Message-ID: <1991Feb14.040136.27388@dirtydog.ima.isc.com>
Date: 14 Feb 91 04:01:36 GMT
References: <1212@tredysvr.Tredydev.Unisys.COM> <1991Jan29.210100.8105@zoo.toronto.edu> <BEVAN.91Jan30084205@rhino.cs.man.ac.uk> <1991Jan31.172147.21397@zoo.toronto.edu> <23134@netcom.COM> <3377@unisoft.UUCP>
Sender: news@dirtydog.ima.isc.com (NEWS ADMIN)
Reply-To: karl@ima.isc.com (Karl Heuer)
Organization: Interactive Systems, Cambridge, MA 02138-5302
Lines: 25

In article <3377@unisoft.UUCP> greywolf@unisoft.UUCP (The Grey Wolf) writes:
>Is there/will there ever be a compile-time / cpp-time evaluation as to
>what types are defined?  For example:
>#if typed(stat_t) ...

Unlikely.  In the traditional implementation, the preprocessor has no way of
knowing anything about declared types.

>This would eliminate the need for putting that stuff in .h files like
>#ifndef _STAT_H_

A simpler solution would be to make typedefs idempotent, like macros.  (Since
a conforming implementation must already handle nested-scope typedefs like
	typedef int foo;
	void f(void) { typedef int foo; }
I doubt that handling same-scope typedefs correctly would be any worse.)

Unfortunately, ANSI didn't define it that way, so the best you can do in a
portable header is to use a guard macro.

>Also, do typedefs ever make it into an object's/executable's nlist?

I believe some compilers will do this if debugging is enabled.

Karl W. Z. Heuer (karl@ima.isc.com or uunet!ima!karl), The Walking Lint