From owner-freebsd-current  Sat Jun 15 20:56: 7 2002
Delivered-To: freebsd-current@freebsd.org
Received: from mailman.zeta.org.au (mailman.zeta.org.au [203.26.10.16])
	by hub.freebsd.org (Postfix) with ESMTP
	id 80A6237B400; Sat, 15 Jun 2002 20:56:04 -0700 (PDT)
Received: from bde.zeta.org.au (bde.zeta.org.au [203.2.228.102])
	by mailman.zeta.org.au (8.9.3/8.8.7) with ESMTP id NAA26742;
	Sun, 16 Jun 2002 13:55:59 +1000
Date: Sun, 16 Jun 2002 14:00:36 +1000 (EST)
From: Bruce Evans <bde@zeta.org.au>
X-X-Sender: bde@gamplex.bde.org
To: Terry Lambert <tlambert2@mindspring.com>
Cc: Maxime Henrion <mux@FreeBSD.ORG>, <current@FreeBSD.ORG>
Subject: Re: duplicate -ffreestanding in kernel build
In-Reply-To: <3D0B9B9C.DB27DD33@mindspring.com>
Message-ID: <20020616134100.M1933-100000@gamplex.bde.org>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Sender: owner-freebsd-current@FreeBSD.ORG
Precedence: bulk
List-ID: <freebsd-current.FreeBSD.ORG>
List-Archive: <http://docs.freebsd.org/mail/> (Web Archive)
List-Help: <mailto:majordomo@FreeBSD.ORG?subject=help> (List Instructions)
List-Subscribe: <mailto:majordomo@FreeBSD.ORG?subject=subscribe%20freebsd-current>
List-Unsubscribe: <mailto:majordomo@FreeBSD.ORG?subject=unsubscribe%20freebsd-current>
X-Loop: FreeBSD.ORG

On Sat, 15 Jun 2002, Terry Lambert wrote:

> Maxime Henrion wrote:
> > Terry Lambert wrote:
> > > What exactly does this do, besides implying "-fno-builtin"?
> > >
> > > The documentation says "and implies main has no special requirements"...
> > >
> > > Neither the kernel nor modules have a "main", so the only thing that's
> > > relevent here is the "-fno-builtin", right?
> >
> > IIRC, -ffreestanding prevented GCC3 from being stupid optimizations like
                                                   ^^^^^^ smart
> > changing occurences of printf("constant string\n") to puts("constant
> > string"), which failed for kernel builds since we don't have puts() in
> > the kernel...
>
> That is an incredibly *fugly* "optimization".  It assumes that I
> use libc, unless I have "-ffreestanding", and it assumes my
> implementation of printf vs. puts.

This is a routine optimization.  It assumes that you use a C compiler
(printf and even libc might not exist, since they might be builtins).
A non-routine optimization might involve building hardware to run the
application and emitting the 1 bit instruction to turn the hardware on.

Bruce


To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-current" in the body of the message