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Re: [PATCH] hash: extend module to deal with non-pointer keys

From: Paul Eggert
Subject: Re: [PATCH] hash: extend module to deal with non-pointer keys
Date: Thu, 01 Jul 2010 15:39:32 -0700
User-agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv: Gecko/20100423 Thunderbird/3.0.4

Re the patch you just reported in:

I assume this is to support the du performance improvement that was proposed in
<http://debbugs.gnu.org/db/65/6524.html>.  I see that you incorporated a further
improvement in the gnulib patch, namely, support for NULL keys.

The gnulib change seems fine, but I noticed some problems with the coreutils
part of that earlier proposal.  Among other things, it makes du dump core on a
(large) test case that I have locally.  I don't know why (perhaps there
were further fixes to the gnulib part that I didn't get right?).  I found
out about the core dump only because I had independently prepared a patch
that I think is better: it uses a bit less memory and is quite a bit simpler.
I'll try to merge my patch with your gnulib change and send it off to
bug-coreutils in the next day or two.

My patch, by the way, doesn't hash pointer keys: it just uses size_t values
and casts them to void * (which is what the hash package wants).  This trick
works on all architectures that I know about, but it isn't guaranteed by
C or POSIX and the casts are a bit offputting, so it'd be nice if the hash
package supported hashing size_t keys directly.  That's lower priority, though.

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