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Re: GTY and const
On Wed, 2004-12-22 at 21:06 -0800, Zack Weinberg wrote:
> Geoff Keating <geoffk@geoffk.org> writes:
>
> > On 22/12/2004, at 3:10 PM, Zack Weinberg wrote:
> >> Daniel Berlin <dberlin@dberlin.org> writes:
> >>> On Tue, 2004-12-21 at 11:01 -0800, Zack Weinberg wrote:
> >> While what you say is true¹, this particular data structure needs
> >> to be in GC memory not because it can point to other things that
> >> are in GC memory, but because it's part of a precompiled header.
> >
> > And, as a consequence of this, these data structures are not truly
> > write-once; any pointers contained in them will be changed by saving
> > a PCH.
>
> Sure; however, that happens behind the back of the code that uses this
> data structure. The 'const' is correctly placed to catch bugs in that
> code, which is what I care about.
>
> > [I think I disagree with Dan's statement, but I'm not sure what he
> > means by "GC allocate". Certainly all roots need to be under control
> > of the GC machinery. Equally certainly, not all roots need to be in
> > memory that can be freed, and there are two obvious counterexamples in
> > the current compiler, static variables and PCH files.]
>
> I think Dan wants to be able to dynamically declare roots which are
> somewhere in malloc space, or something like that.
Yes.
>
> zw