Bill Lear <rael@xxxxxxxxxx> writes:
>>How big is this pack, what platform are you working on and whose
>>SHA-1 implementation do you use?
>
> In order:
>
> % cd .git/objects/pack
> % ls -l
> -r--r--r-- 1 rael software 77360 Feb 13 10:18 pack-23d1a9af78b4b78d...
> -r--r--r-- 1 rael software 87874337 Feb 14 10:00 pack-23d1a9af78b4b78d...
>
> [output of ls trimmed to width]
>
> % uname -a
> Linux lisa.zopyra.com 2.6.9-34.0.2.ELsmp #1 SMP Fri Jul 7 18:22:55 CDT 2006 x86_64 x86_64 x86_64 GNU/Linux
>
> I don't know which SHA-1 implementation I use --- I just installed git
> and off I went. I do see this:
>
> % which sha1sum
> /usr/bin/sha1sum
> % sha1sum --version
> shasum (coreutils) 5.2.1
> Written by Ulrich Drepper and Scott Miller.
> [...]
>
> But I'm not sure which library is in use --- how do I know?
"ldd ~/git-master/bin/git" tells me that it links with libcrypto.so,
so I am using OpenSSL's SHA-1 implementation. I do not know
what your distro uses (or you hand built git yourself?).
I asked this question, because...
>>Also, do you have a huge blob in the repository? I do not know
>>if it is related but the write_sha1_file_prepare() function on
>>the codepath to write loose objects out would trigger the same
>>bug...
>
> I don't know what "huge" is, but the pack file seems to be the largest
> and then one of the objects is listed at 28,604,986 bytes, but nothing
> else is very large.
... we had a problem that some SHA-1 implementation gave bogus
results when we did this:
SHA_CTX ctx;
unsigned char sha1[20];
SHA1_Init(&ctx);
/* hash len bytes starting from buf */
SHA1_Update(&ctx, buf, len);
SHA1_Final(sha1, &ctx);
and asked to hash a large buffer in one go. One of the SHA1
implementations we ship ourselves (I think it was handcrafted
PPC one) used to have problems. But I do not think 27MB is
large enough to trigger such a library bug (the bug was integer
wraparound of a bit counter, I think).
So it looks more and more like a bit decay as Linus suspected...
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