From: Daniel Berlin <dberlin@dberlin.org>
To: Zack Weinberg <zack@codesourcery.com>
Cc: Geoffrey Keating <geoffk@geoffk.org>, gcc@gcc.gnu.org
Subject: Re: GTY and const
Date: Wed, 22 Dec 2004 23:11:00 -0000 [thread overview]
Message-ID: <1103756747.20660.27.camel@linux.site> (raw)
In-Reply-To: <877jnbiih7.fsf@codesourcery.com>
On Tue, 2004-12-21 at 11:01 -0800, Zack Weinberg wrote:
> Geoffrey Keating <geoffk@geoffk.org> writes:
>
> >> > Would it be better to add a cast around the assignment or to make
> >> > the GTY code handle const members?
> >>
> >> I'd prefer that you improved gengtype.
> >
> > It's not gengtype, the problem really is that you cannot have const
> > GCed memory, for the same underlying reasons that you cannot free() a
> > const pointer.
>
> No, that's just plain not true. cpplib makes extensive use of 'const'
> to indicate write-once data structures (they are initialized through a
> non-const pointer, of course). Those definitely can be GC memory.
Right. There is a significant difference between what we need to walk
for marking, and what we really need to GC allocate.
Right now we GTY/gc allocate a lot of things just so we can mark some
things they may point to.
The fact that we *have* to do this is *bad*.
Roots are roots, whether they occur in GC memory or not.
The requirement that they be in GC memory is just bogus and an artifact
of the way ggc-page marks.
--Dan
next prev parent reply other threads:[~2004-12-22 23:06 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-14 7:00 Matt Kraai
2004-12-14 10:30 ` Steven Bosscher
2004-12-14 18:35 ` Zack Weinberg
2004-12-21 18:26 ` Geoffrey Keating
2004-12-21 19:01 ` Zack Weinberg
2004-12-22 23:11 ` Daniel Berlin [this message]
2004-12-22 23:24 ` Zack Weinberg
2004-12-23 3:43 ` Geoff Keating
2004-12-23 5:15 ` Zack Weinberg
2004-12-23 5:39 ` Daniel Berlin
[not found] <1103776856.24215.ezmlm@gcc.gnu.org>
2004-12-23 17:09 ` Lucas (a.k.a T-Bird or bsdfan3)
2004-12-23 20:04 ` Robert Dewar
2004-12-24 2:32 ` Marc Espie
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