bug#47761: Guile Segfaulting on guix build -f

[Leo Prikler <leo.prikler@student.tugraz.at>]

Hi Nicolò

Am Dienstag, den 13.04.2021, 23:36 +0200 schrieb Nicolò Balzarotti:
> Hi guix!
> 
> A package definition that used to build fine, recently (don't know
> exactly when) started failing, with guile segfaulting.
> 
> After removing a few things, it seems that the MWE is this:
> 
> echo '(use-modules (guix git-download)) (git-predicate "repo")'>m.scm
> mkdir repo
> guix build -f m.scm
> Segmentation fault
> 
> guix describe:
> 
> guix 2a62425
>    repository URL: https://git.savannah.gnu.org/git/guix.git
>    branch: master
>    commit: 2a624253bc55e2a94f6581d6e790303575436c96
> 
> One of the two computers provides substitute to the other, so maybe
> my
> guile is somehow damaged?  Can any of you reproduce it?
I managed to somewhat isolate the bug even further:

  (let* ((directory  (string-append (canonicalize-path directory) "/"))
         (dot-git    (repository-discover directory)) ; <- here
         (repository (repository-open dot-git))
         (workdir    (repository-working-directory repository))
         (head       (repository-head repository))
         (oid        (reference-target head))
         (commit     (commit-lookup repository oid))
         (tree       (commit-tree commit))
         (files      (tree-list tree)))

repository-discover is an FFI call into libgit2, that appears to be
segfaulting while… trying to prettify some filename?  At least that's
what "git_path_prettify", which lies on the call trace sounds like.

Regards,
Leo