Russ Allbery wrote:
> Josselin Mouette <joss@debian.org> writes:
>> If we use build IDs (and this has quite some advantages, like being able
>> to do more than just dump the ddebs on a repository), this can lead to
>> having the same detached debugging symbols in two binary packages, since
>> sometimes a binary is built twice the same exact way and put in two
>> different binary packages.
>
> Hm, really? The toolchains that I'm familiar with basically never produce
> the same binary twice; something is always slightly different from
> timestamp information. Could you give an example of such a case in the
> archive right now where identical binaries are in multiple packages so
> that I can better understand how this happens?
There are things the linker takes into account for calculating the build id. The
timestamp isn't one of them.
E.g.:
emilio@saturno:/tmp$ echo "main(){}" > a.c; cp a.c b.c; gcc -o a a.c; gcc -o b
b.c; eu-readelf -n a b | grep Build
Build ID: c164b7f24a18b665601cd1d1b9fa0af6afb728bb
Build ID: c164b7f24a18b665601cd1d1b9fa0af6afb728bb
So in cases where you build a package twice with different configure flags, it's
be possible that those don't affect some binaries, getting the same build ids.
E.g., after a build of evince/2.26.1-2 from testing (the package in unstable has
been changed to ship the backends in the library package so this is no longer
the case, but to show this happens):
root@saturno:~/evince-2.26.1# eu-readelf -n
debian/evince/usr/lib/evince/1/backends/*so
debian/evince-gtk/usr/lib/evince/1/backends/*so | grep Build | sort | uniq -c
2 Build ID: 0232654930d90461896f3d58fe08178082a217df
2 Build ID: 08de63310c0ff98c5aac6392d95c7bd6fc502c8b
2 Build ID: 71b914ea23bb199d9d98de2a15a9d07e982a3ae0
2 Build ID: 7a40178124bf7698de230b2298378f08795ddbe5
2 Build ID: 8de5ebfcb2bfceb9ed19a57d6bbc918392e152ec
2 Build ID: c0b63d2ecd7432f0a01441e0794306651c88f5f7
2 Build ID: c3b7f89bda6381e5849819032f842e6870e184b5
2 Build ID: dffdcca3f7a89b4b9da333d7cc638a96ed8b1bc8
Cheers,
Emilio
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