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Re: CVS update: subversion/subversion/libsvn_fs clones-table.c dag.c txn-table.c

From: Karl Fogel <kfogel_at_galois.collab.net>
Date: 2001-01-12 16:23:45 CET

Karl Fogel <kfogel@galois.collab.net> writes:
> Greg Stein <gstein@lyra.org> writes:
> > btw, note that JimB agreed that making the string data const was probably
> > quite fine. He wasn't so sure about the child/sibling pointers.
>
> Ah, okay. (I had thought JimB had some reason to leave them mutable.)

Waitaminnit here. :-) In skel.h, I see the following comment:

   /* [...]

      You'd think that DATA would be a `const char *', but we want to
      create `skel' structures that point into it, and a skel's DATA
      pointer shouldn't be a `const char *', since that would constrain
      how the caller can use the structure. We only want to say that
      *we* won't change it --- we don't want to prevent the caller from
      changing it --- but C's type system doesn't allow us to say that. */
   skel_t *svn_fs__parse_skel (char *data, apr_size_t len,
                               apr_pool_t *pool);
   
I'd like to hear from JimB that this comment is obsolete before I
revert the change.

-K

 
> > On Fri, Jan 12, 2001 at 02:20:48AM -0800, Greg Stein wrote:
> > > Um. What he said.
> > >
> > > [ as if you couldn't guess that's what I'd say... :-) ]
> > >
> > > Cheers,
> > > -g
> > >
> > > On Fri, Jan 12, 2001 at 01:53:22AM +0100, Branko Cibej wrote:
> > > > kfogel@tigris.org wrote:
> > > >
> > > > > User: kfogel
> > > > > Date: 01/01/11 13:21:08
> > > > >
> > > > > Modified: subversion/libsvn_fs clones-table.c dag.c txn-table.c
> > > > > Log:
> > > > > Add casts away from const, to get rid of compiler warnings.
> > > > >
> > > > > We have const strings being passed into functions that take non-const
> > > > > strings, but -- if I understand correctly -- we don't want those
> > > > > functions promising the incoming data will never be changed. After
> > > > > all, the functions are just storing the data directly (non-copying)
> > > > > into skels, and it would be too restrictive if all skels had to
> > > > > promise never to modify the data in their strings.
> > > > >
> > > > > If this is wrong, and skels can make such a promise, then we should do
> > > > > this change the other way, adding const to the string parameters of
> > > > > svn_fs__str_atom(), svn_fs__parse_skel(), and svn_fs__str_to_dbt().
> > > >
> > > > Well, skels don't change their contents directly right now, and there's
> > > > no API for that. I'm +1e5 for constifying those parameters, and also the
> > > > data pointers within the skels (not the child and sibling pointers, of
> > > > course).
> > > >
> > > > Anyway, if we're going to point from skels into constant strings, we'd
> > > > better make sure those pointers are to const, or we'll regret it
> > > > someday. I think the casts in this case are dangerous. If we can't agree
> > > > to constify the pointers, then I'd rather see we leave the warnings
> > > > rather than add the casts. At the very least, the poor guy that's gonna
> > > > have to fix the segfaults will know where to look.
> > > >
> > > >
> > > > --
> > > > Brane Cibej
> > > > home: <brane_at_xbc.nu> http://www.xbc.nu/brane/
> > > > work: <branko.cibej_at_hermes.si> http://www.hermes-softlab.com/
> > > > ACM: <brane_at_acm.org> http://www.acm.org/
> > > >
> > >
> > > --
> > > Greg Stein, http://www.lyra.org/
> >
> > --
> > Greg Stein, http://www.lyra.org/
Received on Sat Oct 21 14:36:19 2006

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