Skip to content

gh-150075: tar.addfile() doesn't set member offsets#150131

Open
grantlouisherman wants to merge 3 commits into
python:mainfrom
grantlouisherman:fix-150075-tar-addfile-no-offsets
Open

gh-150075: tar.addfile() doesn't set member offsets#150131
grantlouisherman wants to merge 3 commits into
python:mainfrom
grantlouisherman:fix-150075-tar-addfile-no-offsets

Conversation

@grantlouisherman
Copy link
Copy Markdown

@grantlouisherman grantlouisherman commented May 19, 2026 •
edited by bedevere-app Bot
Loading

Original bug report:

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

Fix
I added the offset info for a given file based on the current offset of the file and then after the block size is calculated. I also included a test to validate the behavior

@grantlouisherman
fix(150075): adding tarinfo offset info before and after reading the …
190b3ef 
…file

Signed-off-by: Grant Herman <grantlouisherman041@gmail.com>
@bedevere-app
Copy link
Copy Markdown

bedevere-app Bot commented May 19, 2026

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

@python-cla-bot
Copy link
Copy Markdown

python-cla-bot Bot commented May 19, 2026 •
edited
Loading

All commit authors signed the Contributor License Agreement.

CLA signed

@bedevere-app bedevere-app Bot mentioned this pull request May 19, 2026
Open
@grantlouisherman
Copy link
Copy Markdown
Author

grantlouisherman commented May 20, 2026

I dont think the news is necessary it seems like a pretty minor addition

@bedevere-app
Copy link
Copy Markdown

bedevere-app Bot commented May 20, 2026

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

@grantlouisherman
Copy link
Copy Markdown
Author

grantlouisherman commented May 20, 2026

@ethanfurman should I squash commits?

@bedevere-app
Copy link
Copy Markdown

bedevere-app Bot commented May 20, 2026

Most changes to Python require a NEWS entry. Add one using the blurb_it web app or the blurb command-line tool.

If this change has little impact on Python users, wait for a maintainer to apply the skip news label instead.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment

Reviewers

@ethanfurman ethanfurman Awaiting requested review from ethanfurman ethanfurman is a code owner

Assignees

No one assigned

Labels

awaiting review

Projects

None yet

Milestone

No milestone

Development

Successfully merging this pull request may close these issues.

1 participant

@grantlouisherman