GNU bug report logs - #64794
Guile 3.0.9 in guix shell container with emulated FHS throws ldconfig error @ a050897

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Juliana Sims <juli <at> incana.org>
To: bug-guix <at> gnu.org
Subject: Guile 3.0.9 in guix shell container with emulated FHS throws ldconfig
 error @ a050897
Date: Sat, 22 Jul 2023 20:58:33 -0400

[Message part 1 (text/plain, inline)]

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

[Message part 2 (text/html, inline)]

Message #8 received at 64794 <at> debbugs.gnu.org (full text, mbox):

From: Simon Tournier <zimon.toutoune <at> gmail.com>
To: Juliana Sims <juli <at> incana.org>, 64794 <at> debbugs.gnu.org
Subject: Re: bug#64794: Guile 3.0.9 in guix shell container with emulated
 FHS throws ldconfig error @ a050897
Date: Wed, 20 Sep 2023 08:55:53 +0200

Hi,

On Sat, 22 Jul 2023 at 20:58, Juliana Sims <juli <at> 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 <at> 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

Message #11 received at 64794 <at> debbugs.gnu.org (full text, mbox):

From: Rostislav Svoboda <rostislav.svoboda <at> gmail.com>
To: 64794 <at> debbugs.gnu.org
Subject: Re: Guile 3.0.9 in guix shell container with emulated FHS throws
 ldconfig error @ a050897
Date: Thu, 20 Jun 2024 15:00:33 +0200

The warning appears also for guile <at> 2.0 and later. guile <at> 1.8 works fine:

```
$ guix shell --emulate-fhs --container guile <at> 1.8
[env]$ exit
$ guix shell --emulate-fhs --container guile <at> 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]$
```

Message #14 received at 64794 <at> debbugs.gnu.org (full text, mbox):

From: Thiago Jung Bauermann <bauermann <at> kolabnow.com>
To: Rostislav Svoboda <rostislav.svoboda <at> gmail.com>
Cc: 64794 <at> debbugs.gnu.org
Subject: Re: bug#64794: Guile 3.0.9 in guix shell container with emulated
 FHS throws ldconfig error @ a050897
Date: Thu, 20 Jun 2024 13:17:44 -0300

Hello,

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

> The warning appears also for guile <at> 2.0 and later. guile <at> 1.8 works fine:
>
> ```
> $ guix shell --emulate-fhs --container guile <at> 1.8
> [env]$ exit
> $ guix shell --emulate-fhs --container guile <at> 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

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