Re: What is wrong with these few lines of guile code?

[Mike]

On 10/31/2017 09:41 AM, Hartmut Goebel wrote:
> Hallo,
>
> i replaced the code of gnu/system/install.scm(make-cow-store target) [1]
> with the code below. Now when running this code (which is triggered by
> "herd start cow-store /mnt" in the installation-os)|I get this error:
> |
>
> herd: exception caught while executing 'start' on service 'cow-store':
> ERROR: Unbound variable: gexp
>
> What is wrong with this code? (Parentheses are matching, of course :-)
I'm a Scheme novice, but is your use of 'target' instead of '#$target' 
further down the definition body a problem?  Or is that a proper use of 
Guile macros?

-Mike

> [1]
> https://git.savannah.gnu.org/cgit/guix.git/tree/gnu/system/install.scm#n70
>
> (define (make-cow-store target)
>    "Return a gexp that makes the store copy-on-write, using TARGET as the
> backing store.  This is useful when TARGET is on a hard disk, whereas the
> current store is on a RAM disk."
>
>    (define (set-store-permissions directory)
>      ;; Set the right perms on DIRECTORY to use it as the store.
>      #~(begin
>          (chown #$directory 0 30000)             ;use the fixed
> 'guixbuild' GID
>          (chmod #$directory #o1775)))
>
>    #~(begin
>        ;; Bind-mount TARGET's /tmp in case we need space to build things.
>        (let ((tmpdir (string-append #$target "/tmp")))
>          (mkdir-p tmpdir)
>          (mount tmpdir "/tmp" "none" MS_BIND))
>
>        (let* ((rw-dir (string-append target #$%backing-directory))
>               ;; FIXME: calculate work-dir from backing-directory:
>               ;; normpath(backing-directory + "../.overlayfs-workdir")
>               (work-dir (string-append target "/tmp/.overlayfs-workdir")))
>          (mkdir-p rw-dir)
>          (mkdir-p work-dir)
>          (mkdir-p "/.rw-store")
>          #$(set-store-permissions #~rw-dir)
>          #$(set-store-permissions "/.rw-store")
>
>          ;; Mount the overlay, then atomically make it the store.
>          (mount "none" "/.rw-store" "overlay"
>                 (string-append "lowerdir=" #$(%store-prefix)
>                                "upperdir=" #~rw-dir ","
>                                "workdir=" #~work-dir))
>          (mount "/.rw-store" #$(%store-prefix) "" MS_MOVE)
>          (rmdir "/.rw-store"))))