Debian Bug report logs - #1105149
g-ir-scanner cross wrapper does not interact well with cross building Python extensions

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Message #5 received at submit@bugs.debian.org (full text, mbox, reply):

From: Helmut Grohne <helmut@subdivi.de>

To: Debian Bug Tracking System <submit@bugs.debian.org>

Subject: g-ir-scanner cross wrapper does not interact well with cross building Python extensions

Date: Mon, 12 May 2025 07:52:53 +0200

Package: gobject-introspection
Version: 1.84.0-1
X-Debbugs-Cc: debian-cross@lists.debian.org

I observed that zbar was not using qemu during g-ir-scanner and looked
into it. It turns out that I was patching it to export
_PYTHON_SYSCONFIGDATA_NAME as it would build a Python extension module.
That variable leaked into the part of the build where it runs
g-ir-scanner. It ended up calling the cross wrapper. Unfortunately,
there is a short cut "if sysconfig.get_config_var('MULTIARCH') ==
DEB_HOST_MULTIARCH". The left hand gets influenced by setting
_PYTHON_SYSCONFIGDATA_NAME and therefore the short cut is taken
disabling qemu.

Can we change this short cut to avoid this trap? Any suggestions for
how?

Thanks for considering

Helmut

Message #10 received at 1105149@bugs.debian.org (full text, mbox, reply):

From: Simon McVittie <smcv@debian.org>

To: Helmut Grohne <helmut@subdivi.de>, 1105149@bugs.debian.org

Cc: debian-cross@lists.debian.org

Subject: Re: Bug#1105149: g-ir-scanner cross wrapper does not interact well with cross building Python extensions

Date: Mon, 12 May 2025 13:01:05 +0100

On Mon, 12 May 2025 at 07:52:53 +0200, Helmut Grohne wrote:
>It ended up calling the cross wrapper. Unfortunately,
>there is a short cut "if sysconfig.get_config_var('MULTIARCH') ==
>DEB_HOST_MULTIARCH". The left hand gets influenced by setting
>_PYTHON_SYSCONFIGDATA_NAME and therefore the short cut is taken
>disabling qemu.

And what was the result? Failing to run the scanner because it was a 
host-architecture executable and you don't have transparent qemu 
emulation of the host architecture on the build architecture?

I was hoping that sysconfig.get_config_var('MULTIARCH') would return the 
hard-coded architecture of the running Python interpreter, which would 
have meant that this shortcut was correct. But if your override for 
cross-building makes sysconfig describe the host architecture rather 
than the build architecture, then yes this is wrong.

Is there anything - perhaps in sys or platform rather than sysconfig - 
that would tell us, specifically, the architecture of the running Python 
interpreter? Unfortunately I don't see anything immediately useful in 
the documentation of those modules.

The sysconfig API documentation says "The sysconfig module provides 
access to Python’s configuration information like the list of 
installation paths and the configuration variables relevant for the 
current platform" which unfortunately doesn't really help us to decide 
whether it refers to the host or build platform: either one of those 
could reasonably be described as "current".

I think g-ir-scanner is probably slow enough that an exec of the CAN_RUN 
helper before we run the actual scanner is not a significant slowdown, 
so I think dropping this shortcut would probably be OK. Please could you 
propose a tested merge request or patch?

Are you targeting this for a trixie freeze exception, or for forky?

    smcv

Message #15 received at 1105149@bugs.debian.org (full text, mbox, reply):

From: Helmut Grohne <helmut@subdivi.de>

To: Simon McVittie <smcv@debian.org>

Cc: 1105149@bugs.debian.org, debian-cross@lists.debian.org

Subject: Re: Bug#1105149: g-ir-scanner cross wrapper does not interact well with cross building Python extensions

Date: Mon, 12 May 2025 17:04:47 +0200

Hi Simon,

thanks for your quick followup.

On Mon, May 12, 2025 at 01:01:05PM +0100, Simon McVittie wrote:
> On Mon, 12 May 2025 at 07:52:53 +0200, Helmut Grohne wrote:
> > It ended up calling the cross wrapper. Unfortunately,
> > there is a short cut "if sysconfig.get_config_var('MULTIARCH') ==
> > DEB_HOST_MULTIARCH". The left hand gets influenced by setting
> > _PYTHON_SYSCONFIGDATA_NAME and therefore the short cut is taken
> > disabling qemu.
> 
> And what was the result? Failing to run the scanner because it was a
> host-architecture executable and you don't have transparent qemu emulation
> of the host architecture on the build architecture?

You correctly completed what I left implicit.

> I was hoping that sysconfig.get_config_var('MULTIARCH') would return the
> hard-coded architecture of the running Python interpreter, which would have
> meant that this shortcut was correct. But if your override for
> cross-building makes sysconfig describe the host architecture rather than
> the build architecture, then yes this is wrong.

The sysconfig module is extensively used while cross building Python
extension modules. Therefore, it describes the host architecture in
common build scenarios indeed.

> Is there anything - perhaps in sys or platform rather than sysconfig - that
> would tell us, specifically, the architecture of the running Python
> interpreter? Unfortunately I don't see anything immediately useful in the
> documentation of those modules.

I concur. In an interpreter with _PYTHON_SYSCONFIGDATA_NAME set, both
sys and platform describe the build architecture, but the interfaces
they provide are not exactly useful in telling the build architecture.

> I think g-ir-scanner is probably slow enough that an exec of the CAN_RUN
> helper before we run the actual scanner is not a significant slowdown, so I
> think dropping this shortcut would probably be OK. Please could you propose
> a tested merge request or patch?

The Python interpreter startup we incur via cross-g-ir-tool should be
larger than CAN_RUN already. I concur that dropping the short-cut should
fix the issue at hand. I've copied d-cross@l.d.o to acquire some more
ideas before moving forward with that approach.

> Are you targeting this for a trixie freeze exception, or for forky?

The proposed change bears a bit of risk as it may influence native
builds. It also affects a small minority of packages. I suggest
deferring this to forky.

Helmut

Message #18 received at 1105149-submitter@bugs.debian.org (full text, mbox, reply):

From: Simon McVittie <noreply@salsa.debian.org>

To: 1105149-submitter@bugs.debian.org

Subject: Bug#1105149 marked as pending in gobject-introspection

Date: Thu, 14 Aug 2025 10:24:24 +0000

Control: tag -1 pending

Hello,

Bug #1105149 in gobject-introspection reported by you has been fixed in the
Git repository and is awaiting an upload. You can see the commit
message below and you can check the diff of the fix at:

https://salsa.debian.org/gnome-team/gobject-introspection/-/commit/cedb1da00b5962077d377e704b5db2eafd27e33a

------------------------------------------------------------------------
d/cross-g-ir-tool.in: Don't rely on sysconfig

During cross-compilation of some packages it is necessary to set
the environment variable _PYTHON_SYSCONFIGDATA_NAME, which alters
sysconfig to describe the host rather than build architecture,
meaning that it no longer has facts about the current interpreter.

Closes: #1105149
------------------------------------------------------------------------

(this message was generated automatically)
-- 
Greetings

https://bugs.debian.org/1105149

Message #25 received at 1105149@bugs.debian.org (full text, mbox, reply):

From: Simon McVittie <smcv@debian.org>

To: Helmut Grohne <helmut@subdivi.de>, 1105149@bugs.debian.org

Cc: debian-cross@lists.debian.org

Subject: Re: Bug#1105149: g-ir-scanner cross wrapper does not interact well with cross building Python extensions

Date: Thu, 14 Aug 2025 11:27:21 +0100

On Mon, 12 May 2025 at 17:04:47 +0200, Helmut Grohne wrote:
>The Python interpreter startup we incur via cross-g-ir-tool should be
>larger than CAN_RUN already. I concur that dropping the short-cut should
>fix the issue at hand.

Now that forky development has started, I've queued up that change.

I checked the equivalent cross wrappers in src:glib2.0, but they are so 
much simpler that they already did not have an equivalent bug.

    smcv

Message #30 received at 1105149-close@bugs.debian.org (full text, mbox, reply):

From: Debian FTP Masters <ftpmaster@ftp-master.debian.org>

To: 1105149-close@bugs.debian.org

Subject: Bug#1105149: fixed in gobject-introspection 1.86.0-1

Date: Sat, 13 Sep 2025 15:04:49 +0000

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

Source: gobject-introspection
Source-Version: 1.86.0-1
Done: Jeremy Bícha <jbicha@ubuntu.com>

We believe that the bug you reported is fixed in the latest version of
gobject-introspection, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1105149@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Jeremy Bícha <jbicha@ubuntu.com> (supplier of updated gobject-introspection package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)


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Hash: SHA512

Format: 1.8
Date: Sat, 13 Sep 2025 08:39:09 -0400
Source: gobject-introspection
Built-For-Profiles: noudeb
Architecture: source
Version: 1.86.0-1
Distribution: experimental
Urgency: medium
Maintainer: Debian GNOME Maintainers <pkg-gnome-maintainers@lists.alioth.debian.org>
Changed-By: Jeremy Bícha <jbicha@ubuntu.com>
Closes: 1105149
Changes:
 gobject-introspection (1.86.0-1) experimental; urgency=medium
 .
   [ Jeremy Bícha ]
   * New upstream release
 .
   [ Simon McVittie ]
   * d/cross-g-ir-tool.in: Don't rely on sysconfig.
     During cross-compilation of some packages it is necessary to set
     the environment variable _PYTHON_SYSCONFIGDATA_NAME, which alters
     sysconfig to describe the host rather than build architecture,
     meaning that it no longer has facts about the current interpreter.
     (Closes: #1105149)
   * Improve documentation in README.Debian:
     - Simplify recommended gobject-introspection dependency to 1.80.
       The previous recommendation was new in Debian 13 and Ubuntu 24.04,
       but 1.80 is available in both of those releases too, so we can
       recommend something shorter and easier to remember without losing
       portability.
     - Suggest a less intrusive workaround for #1060838/#1111001
     - #1060907 in haskell-haskell-gi was fixed
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Message #35 received at 1105149-close@bugs.debian.org (full text, mbox, reply):

From: Debian FTP Masters <ftpmaster@ftp-master.debian.org>

To: 1105149-close@bugs.debian.org

Subject: Bug#1105149: fixed in gobject-introspection 1.86.0-2

Date: Thu, 18 Sep 2025 19:18:14 +0000

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

Source: gobject-introspection
Source-Version: 1.86.0-2
Done: Jeremy Bícha <jbicha@ubuntu.com>

We believe that the bug you reported is fixed in the latest version of
gobject-introspection, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1105149@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Jeremy Bícha <jbicha@ubuntu.com> (supplier of updated gobject-introspection package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)


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Hash: SHA512

Format: 1.8
Date: Thu, 18 Sep 2025 14:55:11 -0400
Source: gobject-introspection
Built-For-Profiles: noudeb
Architecture: source
Version: 1.86.0-2
Distribution: unstable
Urgency: medium
Maintainer: Debian GNOME Maintainers <pkg-gnome-maintainers@lists.alioth.debian.org>
Changed-By: Jeremy Bícha <jbicha@ubuntu.com>
Closes: 1105149
Changes:
 gobject-introspection (1.86.0-2) unstable; urgency=medium
 .
   * Release to unstable
 .
 gobject-introspection (1.86.0-1) experimental; urgency=medium
 .
   [ Jeremy Bícha ]
   * New upstream release
 .
   [ Simon McVittie ]
   * d/cross-g-ir-tool.in: Don't rely on sysconfig.
     During cross-compilation of some packages it is necessary to set
     the environment variable _PYTHON_SYSCONFIGDATA_NAME, which alters
     sysconfig to describe the host rather than build architecture,
     meaning that it no longer has facts about the current interpreter.
     (Closes: #1105149)
   * Improve documentation in README.Debian:
     - Simplify recommended gobject-introspection dependency to 1.80.
       The previous recommendation was new in Debian 13 and Ubuntu 24.04,
       but 1.80 is available in both of those releases too, so we can
       recommend something shorter and easier to remember without losing
       portability.
     - Suggest a less intrusive workaround for #1060838/#1111001
     - #1060907 in haskell-haskell-gi was fixed
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