bug#64794: Guile 3.0.9 in guix shell container with emulated FHS throws ldconfig error @ a050897

bug#64794: Guile 3.0.9 in guix shell container with emulated FHS throws ldconfig error @ a050897

[Juliana Sims]

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Hi,

When entering `guix shell -CF guile[@3]`,  I receive the following 
error:
"ldconfig: /lib/libguile-3.0.so.1.6.0-gdb.scm is not an ELF file - it 
has the wrong magic bytes at the start."

Here is the information for my version of Guix:
```
(channel
        (name 'guix)
        (url "<https://git.savannah.gnu.org/git/guix.git>")
        (branch "master")
        (commit
          "a0508975dd6c70a2d2997a75c302a9fd42f7c370")
        (introduction
          (make-channel-introduction
            "9edb3f66fd807b096b48283debdcddccfea34bad"
            (openpgp-fingerprint
              "BBB0 2DDF 2CEA F6A8 0D1D  E643 A2A0 6DF2 A33A 54FA")))
```

Thanks,
Juli


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bug#64794: Guile 3.0.9 in guix shell container with emulated FHS throws ldconfig error @ a050897

[Simon Tournier]

Hi,

On Sat, 22 Jul 2023 at 20:58, Juliana Sims <juli@incana.org> wrote:

> When entering `guix shell -CF guile[@3]`,  I receive the following 
> error:
> "ldconfig: /lib/libguile-3.0.so.1.6.0-gdb.scm is not an ELF file - it 
> has the wrong magic bytes at the start."

[...]

>         (commit
>           "a0508975dd6c70a2d2997a75c302a9fd42f7c370")

I confirm the message:

--8<---------------cut here---------------start------------->8---
$ guix shell -CF guile@3
ldconfig: /lib/libguile-3.0.so.1.6.0-gdb.scm is not an ELF file - it has the wrong magic bytes at the start.
--8<---------------cut here---------------end--------------->8---

with Guix revision 6113e0529d61df7425f64e30a6bf77f7cfdfe5a5.

Is it a warning or an error?  Other said, which feature does it break?


Cheers,
simon

bug#64794: Guile 3.0.9 in guix shell container with emulated FHS throws ldconfig error @ a050897

[Rostislav Svoboda]

The warning appears also for guile@2.0 and later. guile@1.8 works fine:

```
$ guix shell --emulate-fhs --container guile@1.8
[env]$ exit
$ guix shell --emulate-fhs --container guile@2.0
ldconfig: /lib/libguile-2.0.so.22.8.1-gdb.scm is not an ELF file - it
has the wrong magic bytes at the start.

[env]$
```

bug#64794: Guile 3.0.9 in guix shell container with emulated FHS throws ldconfig error @ a050897

[Thiago Jung Bauermann via Bug reports for GNU Guix]

Hello,

Rostislav Svoboda <rostislav.svoboda@gmail.com> writes:

> The warning appears also for guile@2.0 and later. guile@1.8 works fine:
>
> ```
> $ guix shell --emulate-fhs --container guile@1.8
> [env]$ exit
> $ guix shell --emulate-fhs --container guile@2.0
> ldconfig: /lib/libguile-2.0.so.22.8.1-gdb.scm is not an ELF file - it
> has the wrong magic bytes at the start.
>
> [env]$
> ```

The error is harmless. AFAIU ldconfig ignores the non-ELF file and
compiles the ld cache with the ELF shared libraries.

libguile-…-gdb.scm is a GDB extension file¹ that GDB auto-loads when
debugging programs using libguile.so². From the beginning of said .scm
file:

;;; Commentary:
;;;
;;; This file defines GDB extensions to pretty-print 'SCM' objects, and
;;; to walk Guile's virtual machine stack.
;;;
;;; This file is installed under a name that follows the convention that
;;; allows GDB to auto-load it anytime the user is debugging libguile
;;; (info "(gdb) objfile-gdbdotext file").

In distros using the Filesystem Hierarchy Standard, this file is
installed in GDB's data directory instead of /lib, so ldconfig doesn't
run into it. For example, in Debian/Ubuntu:

$ dpkg -L guile-3.0-dev | grep gdb.scm
/usr/share/gdb/auto-load/libguile-3.0.so.1.6.0-gdb.scm

Unfortunately, in the case of Guix the auto-load directory is in GDB's
own immutable installation directory so Guile can't put it there:

$ gdb -q
(gdb) show auto-load scripts-directory 
List of directories from which to load auto-loaded scripts is $debugdir:$datadir/auto-load.
(gdb) show data-directory 
GDB's data directory is "/gnu/store/i6x19fvlb1ladc3hcg70hnkcq6i6x232-gdb-14.2/share/gdb".

One way to improve that would be to propose a patch to upstream GDB so
that additional auto-load scripts directories could be specified via an
environment variable. Then Guile and other packages that provided GDB
extentions (such as libstdc++) could install them in their respective
/gnu/store/…-package/share/gdb/auto-load directories, and the Guix
profile could set the GDB environment variable to point to them.

-- 
Thiago

¹ https://sourceware.org/gdb/current/onlinedocs/gdb.html/Guile.html
² https://sourceware.org/gdb/current/onlinedocs/gdb.html/objfile_002dgdbdotext-file.html