[Buildroot] [PATCH next v6 07/10] core: implement per-package SDK and target

Thomas De Schampheleire patrickdepinguin at gmail.com
Fri Jan 11 20:09:40 UTC 2019

El jue., 10 ene. 2019 a las 22:25, Arnout Vandecappelle
(<arnout at mind.be>) escribió:
> On 26/12/2018 19:33, Thomas De Schampheleire wrote:
> > In a similar context I once had following problem:
> > http://lists.busybox.net/pipermail/buildroot/2018-August/226955.html
> > This was for target binaries, rather than host, but for the below
> > discussion it does not matter.
>  I don't think you ever replied to my question in that thread:
>  Let's first find out why it is cleared. patchelf should check for each
> directory in rpath if it is actually needed, and only remove it if it is not
> needed. So, what library do you have in /opt/foobar/lib, and is it really linked
> with the program?
>  Hm, I realize that we never thought about dlopen()ed libraries. Could that be
> the cause? I guess that hasn't been a problem up to now because usually programs
> using dlopen() will use an absolute path (to a build-time or run-time configured
> plugin directory) rather than relying on RPATH.

Sorry that I did not seem to have replied on that question.

The binary in question did in fact link with the library, there is no
dlopen used.
Some redacted output showing the initial rpath, which disappears after

$ readelf -d output/target/opt/foobar/bin/fooprogram | rg 'NEEDED|RPATH'
 0x00000001 (NEEDED)                     Shared library: [libfoo.so.1]
 0x0000000f (RPATH)                      Library rpath:

$ find output/target/ -name libfoo.so.1

$ env HOST_DIR=output/host STAGING_DIR=output/staging
TARGET_DIR=output/target support/scripts/fix-rpath target

$ readelf -d output/target/opt/foobar/bin/fooprogram | rg 'NEEDED|RPATH'
 0x00000001 (NEEDED)                     Shared library: [libfoo.so.1]

> > Looking back at this problem, taking into account the above comment
> > from the patchelf patch, I would say that my problem would have been
> > fixed if case (4) above would not discard the path.
>  I think one motivation for removing redundant rpaths is to avoid having build
> directories leaking into target binaries. Especially for reproducible builds
> this is important.

Ok, I can understand that.
But it should only remove directories which are not present in the
target directory, e.g. if rpath contains /opt/foobar/lib then the
script should check if output/target/opt/foobar/lib exists. If it
does, then the rpath can remain, if it does not then it could be

> > If that change would be adopted, then it would also preserve the rpath
> > '/home/thomas/projets/buildroot/output/per-package/host-e2fsprogs/host/lib'.
> >
> > Of course, in your case you might actually want a different final
> > rpath, i.e. rewrite it to the consolidated host directory. I think
> > that in this case it would be better to read the rpath via patchelf,
> > calculate the transformed rpath from our own script, then writing it
> > back via patchelf,  rather than adding more options into patchelf with
> > e.g. transformation rules.
>  The problem is that patchelf is rather slow, so running it twice is even slower...

How so is it slow, can you clarify? Which times are you talking about?


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