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Re: CVS update: subversion/subversion/libsvn_delta vcdiff_parse.c

From: Greg Stein <gstein_at_lyra.org>
Date: 2000-10-03 23:37:10 CEST

On Tue, Oct 03, 2000 at 04:12:55PM -0500, Karl Fogel wrote:
> Greg Hudson <ghudson@MIT.EDU> writes:
> > > + (svn_txdelta_window_t *) apr_pcalloc (parser->subpool,
> > > + sizeof(svn_txdelta_window_t));
> >
> > So, zeroing out the bytes of a pointer and assuming it will have the
> > value of NULL is not correct C, although it tends to work in practice.
> > (It's also not clean, in my opinion, even with integral types.) So
> > any pointer fields of the allocated svn_txdelta_window_t should not be
> > assumed to be NULL. If you're aware of this and don't care, that's
> > okay, but I thought I'd make sure.
> Oh -- actually, that's why I made that change (plus a much larger one
> right after it). One can't reliably assume that pointer fields in the
> new structure will be NULL after this?

Yes, one can. calloc/apr_pcalloc are designed to zero out the allocated
memory very quickly, and are thus very useful for initializing data
structures. This includes NULL pointers.

See my other note for my rant. apr_pcalloc() is an entirely valid use, and
can prevent a lot of manual field initialization in a structure. Please
don't add manual NULL initializations... that is unnecessary cruft.


Greg Stein, http://www.lyra.org/
Received on Sat Oct 21 14:36:10 2006

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