bug#42558: ‘guix pack -RR’: audit library is dynamically linked

[Ludovic Courtès]

Ludovic Courtès <ludovic.courtes@inria.fr> skribis:

> The audit library created by ‘guix pack -RR’, called ‘pack-audit.so’, is
> dynamically-linked.  Thus, it cannot be loaded (unless there are working
> libgcc.so and libc.so in the search path?), leading to failures like
> this:
>
> $ GUIX_EXECUTION_ENGINE=performance ./bin/sinfo --version
> ERROR: ld.so: object 
> '/…/lcourtes/tmp/t/gnu/store/0n6nnvzgxyisg0bszb5zqxp2gzdwh7h3-pack-audit.so' 
> cannot be loaded as audit interface: cannot open shared object file; ignored.
> /…/lcourtes/tmp/t/gnu/store/3dhy2f3djmm1h5ix5aa84lrskxzrl6d0-slurm-19.05.3-2/bin//sinfo:
>  error while loading shared libraries: libslurmfull.so: cannot open shared 
> object file: No such file or directory
>
> The root cause is that ‘pack-audit.so’ NEEDs libgcc_s.so, which on this
> machine could not be loaded, and thus resolving the other dependencies
> of the wrapped executable, like ‘libslurmfull.so’ here, fails.

Fixed by commit c6c0d5a22c2ee3d7164dab0129b2e4852a4ae76c.

How could this happen?  I think there are two key factors:

  1. Most likely I tested v1 of the patch series on “real” non-Guix
     machines, but when iterating on v2 (which removed ‘--library-path’
     from the ld.so invocation¹) I probably relied on
     ‘tests/guix-pack-relocatable.sh’, which emulates a machine where
     /gnu is empty by mounting a tmpfs on it.

  2. There was another bug in ‘exec_with_loader’ whereby it would
     symlink its store to that writable /gnu.  Thus, the tests would run
     as if the store was already available under /gnu/store, thereby
     hiding the actual issue.  This second bug is fixed by
     c088aa2988ef82289c87ebfd6d07d8f1464dd8f0.

AFAICS we’re all fine now.

You’re very welcome to give it a spin on a Guix-less machine!  Just do:

  guix pack -RR your favorite packages -S /bin=bin

Send the resulting tarball to that machine, and then:

  mkdir test
  cd test
  tar xf /path/to/pack.tar.gz
  GUIX_EXECUTION_ENGINE=fakechroot ./bin/your-favorite-command

Ludo’.

¹ https://issues.guix.gnu.org/41189#8