#1364 Regression: compatibility with old versions


Files created using 7-Zip Gui v9.29-9.30 can't be read by programs that use old dll library (eg. 4.57).

Reported at Forum: https://sourceforge.net/p/sevenzip/discussion/45797/thread/9d1f5836?limit=25&page=3#94fa

Example: http://img593.imageshack.us/img593/8550/7zbug.png


  • Sr. Zé Alguém

    Sr. Zé Alguém - 2013-06-28


  • Shell

    Shell - 2013-07-19

    It is a feature rather than a bug. 7-Zip 9.29 uses LZMA2 method by default, which is only supported starting from version 9.04. To retain compatibility, you should manually choose another compression method (for example, LZMA).

    UPDATE: Sorry, didn't notice that you used LZMA. Please, post the erroneous archive here. Perhaps, it is OK, but Beyond Compare itself does something wrong.

    Last edit: Shell 2013-07-19
  • Sr. Zé Alguém

    Sr. Zé Alguém - 2013-07-19

    Yes, I was using LZMA and it happened with any file created in those conditions.
    Do you have a way to test if it is a bug with that program or the library, because the error happens only with files created by those newer versions?

  • Shell

    Shell - 2013-07-30

    Sorry for delay. The simplest thing I think of is to test the archive with an old 7za (7-Zip standalone). If it shows an error, then this is really 7-Zip's problem. If not, the problem is in your application.

  • Sr. Zé Alguém

    Sr. Zé Alguém - 2013-12-01


    Right now I took some time to test old versions against this issue.
    My tests were made using the traditional GUI program (7zFM.exe)

    Versions 4.58beta and older cannot read files created by 7-Zip v9.26-9.31
    These old versions can read files created by the latter versions using LZMA2 but not LZMA.


  • Igor Pavlov

    Igor Pavlov - 2013-12-01

    New 7-Zip uses "Unknown" field in header to align data blocks.

    7-Zip 4.50 - 4.58 contain BUG, so they do not support .7z archives with "Unknown" field in header.
    Another versions probably work correctly.

  • Sr. Zé Alguém

    Sr. Zé Alguém - 2013-12-01

    Nice to know, thanks.
    So, I guess that was fixed in 4.59 as "Some bugs were fixed", right?
    Why don't you describe some bugfixes like this? We like big changelogs :)

    Moving to other subject... I think that what is more important for you to spend your time on is improving the reliability of compression using multi-core, so it achieves the same compression independently of the amount of cores used. Imo, this is one big downside of 7-Zip compared to WinRAR for example, afaik.


Log in to post a comment.