zip --symlink is incompatible with piped output

[James Fraser]

Hi folks,

As in the summary, if you use --symlink (-y) with the output piped to a process, it stops building the zip on the first symlink it encounters with an unhelpful error (as the user is not using -0 intentionally).

Here's the simplest test case I can build:

root@test123:~/test# mkdir asdf
root@test123:~/test# ln -s asdf test
root@test123:~/test# date > hello.txt
root@test123:~/test# ls -l
total 2
drwxr-xr-x 2 root root 4 Aug 20 09:10 asdf
-rw-r--r-- 1 root root 29 Aug 20 08:50 hello.txt
lrwxrwxrwx 1 root root 4 Aug 20 08:24 test -> asdf
root@test123:~/test# zip -1ryv - . | cat > ../test.zip
  adding: test

zip error: Invalid command arguments (zip -0 not supported for I/O on pipes or devices)
66.0 B 0:00:00 [93.4KiB/s] [<=> ]

I believe the issue is around line 575 of zipup.c... my understanding of the code is tenuous at best, but I think q is not reset when m is set to STORE:

    l = issymlnk(a);
    if (l) {
      ifile = fbad;
      m = STORE;
    }
    else if (isdir) { /* directory */
      ifile = fbad;
      m = STORE;
      q = 0;
    }

If I build with q = 0; in the if (l) block too, it appears to work (it complains that the file size changed while zipping, but zip does not error out, the zip file is created correctly), but I don't know what other problems this would introduce.

Not sure if anyone's maintaining this package so I don't want to put too much effort into it, I'll have a go at attaching a patch which I think fixes the issue, but again I'm not sure if it causes any new issues (and one probably wants to fix the warning about the file size changing at the very least).

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Ubuntu Foundations Team Bug Bot (crichton)]

The attachment "fixsymlink.patch" seems to be a patch. If it isn't, please remove the "patch" flag from the attachment, remove the "patch" tag, and if you are a member of the ~ubuntu-reviewers, unsubscribe the team.

[This is an automated message performed by a Launchpad user owned by ~brian-murray, for any issues please contact him.]