Seeking help to create link to libstdc++.so in /lib64

Seeking help to create link to libstdc++.so in /lib64

[Milind Kamble]

Hello,
    I want to create a link in /lib64 that points to libstdc++.so.
That target file is present in the gcc:lib package (not in the
gcc:out). Following the recommendation in Guix info manual (Base
Services), I have used the following construct in my operating-system
spec:
(operating-system
   ;; snip other stuff
  (services
      (list
         ;; snip other stuff
         (extra-special-file "/lib64/libstdc++.so.6"
                    (file-append gcc "/lib/libstdc++.so.6")))))

This creates the link to
/gnu/store/somehash-gcc-10.3.0/lib/libstdc++.so.6 which is a broken
link because libstdc++.so.6 is available in gcc:lib and not gcc:out

I am unable to specify (file-append gcc:lib "/lib/libstdc++.so.6")
because guile complains that gcc:lib is unbound

I understand it is hacky to create link in /lib64/ and the purer
solution is to port the desired app into a guix package. But I don't
have the expertise to craft a package definition yet. I am trying to
use the Deskreen app for screen sharing, which is available as an
AppImage. I have managed to run the AppImage by crafting my
LD_LIBRARY_PATH and "patchelf --set-interpreter" of the AppImage
binary and wanted to make these links in /lib64 where the AppImage
expects it's shared libraries.

Rather than getting a recommendation to not create the link, I would
like to know what syntax change will achieve the desired outcome in
the operating-system spec. This will help me learn the nuances and
concepts of gexp.

If instead of file-append, I use string-append like this:
#~(string-append $#gcc:lib "/lib/libstdc++.so.6")
it works to the extent that gcc:lib is expanded correctly, but then
activate-service.scm script contains
(activate-special-files (quote (("/lib64/libstdc++.so.6"
(string-append "/gnu/store/6d0pl5khj08j3c2619jnypc8bznspgx8-gcc-10.3.0-lib"
"/lib/libstdc++.so.6")))))

and which results in an error:
wrong type (expecting string): (string-append
"/gnu/store//gnu/store/6d0pl5khj08j3c2619jnypc8bznspgx8-gcc-10.3.0.lib"
"/lib/libstdc++.so.6")

So string-append needs to get evaluated in host side before dispatch
to the guix daemon
 Any help would be educative and appreciated.
Thanks,
Milind Kamble

Re: Seeking help to create link to libstdc++.so in /lib64

[phodina]

Hi Milind,



> If instead of file-append, I use string-append like this:
> #~(string-append $#gcc:lib "/lib/libstdc++.so.6")
> it works to the extent that gcc:lib is expanded correctly, but then
> activate-service.scm script contains
> (activate-special-files (quote (("/lib64/libstdc++.so.6"
> (string-append "/gnu/store/6d0pl5khj08j3c2619jnypc8bznspgx8-gcc-10.3.0-lib"
> "/lib/libstdc++.so.6")))))
> 
> and which results in an error:
> wrong type (expecting string): (string-append
> "/gnu/store//gnu/store/6d0pl5khj08j3c2619jnypc8bznspgx8-gcc-10.3.0.lib"
> "/lib/libstdc++.so.6")
> 

IMHO you can try the following code instead of the Gexp:
`(,gcc "lib")

Hope it helps!

----
Petr

Re: Seeking help to create link to libstdc++.so in /lib64

[Milind Kamble]

Thanks for responding Petr. Could you elaborate how to compose it with
the outer function?
I tried this
(operating-system  ;; other stuff snipped out
  (services
      (list
             (extra-special-file "/lib64/libstdc++.so.6"
                         (file-append  `(,gcc "lib") "/lib/libstdc++.so.6"))
))))

It gives me this error:
In procedure struct-vtable: Wrong type argument in position 1
(expecting struct): (#<package gcc@10.3.0 gnu/packages/gcc.scm:659
7fb670d7d0b0> "lib")

So file-append does not like/expect a list. It expects a package
object for first argument

-Milind

On Tue, Nov 1, 2022 at 4:54 AM phodina <phodina@protonmail.com> wrote:
>
> Hi Milind,
>
>
>
> > If instead of file-append, I use string-append like this:
> > #~(string-append $#gcc:lib "/lib/libstdc++.so.6")
> > it works to the extent that gcc:lib is expanded correctly, but then
> > activate-service.scm script contains
> > (activate-special-files (quote (("/lib64/libstdc++.so.6"
> > (string-append "/gnu/store/6d0pl5khj08j3c2619jnypc8bznspgx8-gcc-10.3.0-lib"
> > "/lib/libstdc++.so.6")))))
> >
> > and which results in an error:
> > wrong type (expecting string): (string-append
> > "/gnu/store//gnu/store/6d0pl5khj08j3c2619jnypc8bznspgx8-gcc-10.3.0.lib"
> > "/lib/libstdc++.so.6")
> >
>
> IMHO you can try the following code instead of the Gexp:
> `(,gcc "lib")
>
> Hope it helps!
>
> ----
> Petr

Re: Seeking help to create link to libstdc++.so in /lib64

[(]

Heya,

On Mon Oct 31, 2022 at 3:38 AM GMT, Milind Kamble wrote:
> Hello,
>     I want to create a link in /lib64 that points to libstdc++.so.

You probably want to use the new

  guix shell -CF ...

command; the -F is short for --emulate-fhs.

    -- (

Re: Seeking help to create link to libstdc++.so in /lib64

[phodina]

> You probably want to use the new
> 
> guix shell -CF ...
> 
> command; the -F is short for --emulate-fhs.
> 

This is probably the best approach to run it in a container with FHS.

----
Petr

Re: Seeking help to create link to libstdc++.so in /lib64

[(]

On Mon Oct 31, 2022 at 3:38 AM GMT, Milind Kamble wrote:
> But I don't have the expertise to craft a package definition yet.

It's actually quite easy! If you pop into #guix, i'll help you with it.

    -- (