On Fri, Feb 28, 2025 at 09:57:08PM +0200, Nir Soffer wrote:
> This test depends on TarFile.addfile() to add tar member header without
> writing the member data, which we write ourself using qemu-nbd. Python
> 3.13 changed the function in a backward incompatible way[1] to require a
> file object for tarinfo with non-zero size, breaking the test:
>
> -[{"name": "vm.ovf", "offset": 512, "size": 6}, {"name": "disk",
> "offset": 1536, "size": 393216}]
> +Traceback (most recent call last):
> + File "/home/stefanha/qemu/tests/qemu-iotests/302", line 118, in
> <module>
> + tar.addfile(disk)
> + ~~~~~~~~~~~^^^^^^
> + File "/usr/lib64/python3.13/tarfile.py", line 2262, in addfile
> + raise ValueError("fileobj not provided for non zero-size regular
> file")
> +ValueError: fileobj not provided for non zero-size regular file
>
> The new behavior makes sense for most users, but breaks our unusual
> usage. Fix the test to add the member header directly using public but
> undocumented attributes. This is more fragile but the test works again.
>
> This also fixes a bug in the previous code - when calling addfile()
> without a fileobject, tar.offset points to the start of the member data
> instead of the end.
>
> [1] https://github.com/python/cpython/pull/117988
>
> Signed-off-by: Nir Soffer <nir...@gmail.com>
Reviewed-by: Eric Blake <ebl...@redhat.com>
> ---
> tests/qemu-iotests/302 | 19 ++++++++++++++-----
> 1 file changed, 14 insertions(+), 5 deletions(-)
>
> diff --git a/tests/qemu-iotests/302 b/tests/qemu-iotests/302
> index a6d79e727b..e980ec513f 100755
> --- a/tests/qemu-iotests/302
> +++ b/tests/qemu-iotests/302
> @@ -115,13 +115,22 @@ with tarfile.open(tar_file, "w") as tar:
>
> disk = tarfile.TarInfo("disk")
> disk.size = actual_size
> - tar.addfile(disk)
>
> - # 6. Shrink the tar to the actual size, aligned to 512 bytes.
> + # Since python 3.13 we cannot use addfile() to create the member header.
> + # Add the tarinfo directly using public but undocumented attributes.
>
> - tar_size = offset + (disk.size + 511) & ~511
> - tar.fileobj.seek(tar_size)
> - tar.fileobj.truncate(tar_size)
> + buf = disk.tobuf(tar.format, tar.encoding, tar.errors)
> + tar.fileobj.write(buf)
> + tar.members.append(disk)
> +
> + # Update the offset and position to the location of the next member.
> +
> + tar.offset = offset + (disk.size + 511) & ~511
> + tar.fileobj.seek(tar.offset)
> +
> + # 6. Shrink the tar to the actual size.
> +
> + tar.fileobj.truncate(tar.offset)
>
> with tarfile.open(tar_file) as tar:
> members = [{"name": m.name, "size": m.size, "offset": m.offset_data}
> --
> 2.39.5 (Apple Git-154)
>
>
--
Eric Blake, Principal Software Engineer
Red Hat, Inc.
Virtualization: qemu.org | libguestfs.org
