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To: Zack Weinberg <zack@codesourcery.com>
Cc: gcc@gcc.gnu.org
Subject: Re: GTY and const
References: <20041213203007.GA4907@localhost.localdomain> 
    <87fz28enjk.fsf@codesourcery.com>
From: Geoffrey Keating <geoffk@geoffk.org>
Date: Tue, 21 Dec 2004 18:26:00 -0000
In-Reply-To: <87fz28enjk.fsf@codesourcery.com>
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Zack Weinberg <zack@codesourcery.com> writes:

> Matt Kraai <kraai@ftbfs.org> writes:
> 
> > Howdy,
> >
> > One of the warnings that causes PR 18176 is an assignment of a const
> > cpp_token * to the source member of the val union of the cpp_token
> > structure, which is not const.  According to the uses I've found, this
> > member could be const, except that doing so causes warnings in
> > gtype-desc.c, which does not preserve the const qualifier.
> >
> > 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.