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From: Erik Cederstrand <erik@cederstrand.dk>
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Date: Tue, 5 Oct 2010 15:28:36 +0200
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Subject: Timestamps in static libraries
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Hello hackers,

I got reminded of a problem I had a couple of years back compressing =
FreeBSD jails. I was using bsdiff for the compression and found out that =
md5 sums of static libraries (.a files) in /usr/lib and /usr/local/lib =
didn't match between jails, even though the source code used to create =
the jails hadn't changed. One of my goals is to detect which files in a =
distribution change between two commits.

It turns out that timestamps are stored in the library:

# strings DIR1/usr/lib/libfetch.a > tmp1
# strings DIR2/usr/lib/libfetch.a > tmp2
# diff tmp1 tmp2
2c2
< /               1200728973  0     0     0       954       `
---
> /               1200723259  0     0     0       954       `
57c57
< file.o/         1200728973  0     0     100644  2356      `
---
> file.o/         1200723259  0     0     100644  2356      `
86c86
< http.o/         1200728973  0     0     100644  17180     `
---
> http.o/         1200723258  0     0     100644  17180     `
[...]

I'm wondering if this is necessary, or if this can possibly be turned of =
with a knob somewhere.

Thanks,

Erik=

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