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Date:      Thu, 14 Apr 2016 23:12:11 -0700
From:      Peter Wemm <peter@wemm.org>
To:        svn-src-head@freebsd.org
Cc:        Pedro Giffuni <pfg@freebsd.org>, src-committers@freebsd.org, svn-src-all@freebsd.org
Subject:   Re: svn commit: r297974 - in head/sys: i386/i386 i386/ibcs2 x86/x86
Message-ID:  <208673032.ZrzIEQ39cc@overcee.wemm.org>
In-Reply-To: <570FCFE5.3010304@FreeBSD.org>
References:  <201604141704.u3EH47Vv063976@repo.freebsd.org> <570FCFE5.3010304@FreeBSD.org>

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On Thursday, April 14, 2016 12:14:13 PM Pedro Giffuni wrote:
> On 04/14/16 12:04, Pedro F. Giffuni wrote:
> > Author: pfg
> > Date: Thu Apr 14 17:04:06 2016
> > New Revision: 297974
> > URL: https://svnweb.freebsd.org/changeset/base/297974
> >=20
> > Log:
> >    x86: for pointers replace 0 with NULL.
> >   =20
> >    These are mostly cosmetical, no functional change.
> >   =20
> >    Found with devel/coccinelle.
> >=20
> > Modified:
> >    head/sys/i386/i386/db_disasm.c
> >    head/sys/i386/i386/pmap.c
> >    head/sys/i386/ibcs2/imgact_coff.c
> >    head/sys/x86/x86/nexus.c
>=20
> ...
>=20
> > Modified: head/sys/i386/i386/pmap.c
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D
> > =3D=3D=3D=3D --- head/sys/i386/i386/pmap.c=09Thu Apr 14 16:32:27 20=
16=09
(r297973)
> > +++ head/sys/i386/i386/pmap.c=09Thu Apr 14 17:04:06 2016=09(r297974=
)
> > @@ -269,15 +269,15 @@ pt_entry_t *CMAP3;
> >=20
> >   static pd_entry_t *KPTD;
> >   caddr_t ptvmmap =3D 0;
> >   caddr_t CADDR3;
> >=20
> > -struct msgbuf *msgbufp =3D 0;
> > +struct msgbuf *msgbufp =3D NULL;
> >=20
> >   /*
> >  =20
> >    * Crashdump maps.
> >    */
> >  =20
> >   static caddr_t crashdumpmap;
> >=20
> > -static pt_entry_t *PMAP1 =3D 0, *PMAP2;
> > -static pt_entry_t *PADDR1 =3D 0, *PADDR2;
> > +static pt_entry_t *PMAP1 =3D NULL, *PMAP2;
> > +static pt_entry_t *PADDR1 =3D NULL, *PADDR2;
> >=20
> >   #ifdef SMP
> >   static int PMAP1cpu;
> >   static int PMAP1changedcpu;
>=20
> Hmm .. being static, there is no need to initialize these.

Several eons ago, at least some of these were initialized to force them=
 into=20
the data section so that they had known or safe values before the bss z=
ero=20
pass.  I don't know if that was ever an issue on freebsd, or just the u=
pstream=20
code.  You'd have to look well back into ancient 2.0 or earlier vintage=
 code. =20

I have a vague memory that our early a.out kernel had to zero its own b=
ss=20
because the early a.out boot blocks didn't, and these variables would h=
ave=20
been caught in the crossfire.  Or something..

In any case, I'd be surprised if the compiler didn't put them in the bs=
s=20
section these days anyway.  At least without cc -ffreestanding, anyway.=


=2D-=20
Peter Wemm - peter@wemm.org; peter@FreeBSD.org; peter@yahoo-inc.com; KI=
6FJV
UTF-8: for when a ' or ... just won\342\200\231t do\342\200\246
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