tarfile: addfile() doesn't set member offsets

Bug report

Bug description:

It appears that tarfile.TarFile.addfile() sets neither offset nor offset_data attributes in the TarInfo added to self.members, when it's done adding the file. Members in a reopened TAR have correct values.

Reproducer

from io import BytesIO
from tarfile import TarFile, TarInfo

with TarFile("test.tar", "w") as tar:
    data = b"data"

    tarinfo = TarInfo("test1.txt")
    tarinfo.size = len(data)
    tar.addfile(tarinfo, BytesIO(data))

    tarinfo = TarInfo("test2.txt")
    tarinfo.size = len(data)
    tar.addfile(tarinfo, BytesIO(data))

    for member in tar.getmembers():
        print(member.name, member.offset, member.offset_data)

with TarFile("test.tar", "r") as tar:
    for member in tar.getmembers():
        print(member.name, member.offset, member.offset_data)

Expected output

test1.txt 0 512
test2.txt 1024 1536
test1.txt 0 512
test2.txt 1024 1536

Actual output

test1.txt 0 0
test2.txt 0 0
test1.txt 0 512
test2.txt 1024 1536

CPython versions tested on:

3.15

Operating systems tested on:

Linux

Linked PRs

• gh-150128
• gh-150131
• gh-150278

Commencez par tarfile.TarFile.addfile() et comparez les offsets de TarInfo en mémoire avec les valeurs produites lors de la réouverture de l’archive. Exécutez le reproducteur BytesIO fourni et vérifiez que getmembers() signale les valeurs attendues de offset et offset_data pour les deux membres ; consultez les PRs liées gh-150128, gh-150131 et gh-150278 avant de commencer.