Re: non-deterministic compression results with gzip -n9

[Paul Eggert]

On 12/08/11 02:27, Riku Voipio wrote:
> According to gzip RFC, the last 4 bytes are ISIZE, which should be
> uncompressed input size. Which leaves me rather baffled how that can
> differ on same input files - and how gunzip is completly happy with
> both versions of compressed file, producing the same output.

I looked only at NEWS.amd64.gz and NEWS.armel.gz.  For those two files
your diagnosis does not seem to be right, as these two files do not
differ in the last 4 bytes, but in bytes before then:

$ od -tx1 <NEWS.amd64.gz >NEWS.amd64.gz.od
$ od -tx1 <NEWS.armel.gz >NEWS.armel.gz.od
$ diff -u NEWS.*.gz.od
--- NEWS.amd64.gz.od    2011-12-09 12:03:41.090594754 -0800
+++ NEWS.armel.gz.od    2011-12-09 12:03:57.298663371 -0800
@@ -317,6 +317,6 @@
 0011700 fa 9f da 9b 92 ad 57 44 19 45 c5 42 e5 b6 d9 c2
 0011720 7e 80 02 bd 58 94 33 74 ba 0a 62 24 52 7b 35 33
 0011740 b2 87 51 76 b7 af cc 7f 09 b0 2d 14 d6 8d f9 4d
-0011760 94 51 39 49 cd 87 2e ff 0b 5a 6c 8d f6 80 35 00
+0011760 94 51 39 49 cd f7 50 ff 17 5a 6c 8d f6 80 35 00
 0012000 00
 0012001

So the differences are not in ISIZE.  Can you track down
what's actually differing and why?  (That would save some
time for me when debugging....)  Thanks.