Building For Older Versions

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Once upon a time, Michael Eager said:

Most shared libraries are “upwards compatible” but not “backwards compatible” – builds against an old version will run with the new version, but not the other way around. You’ve found this with glibc, but you could also run into it with other libraries.

Would it be practical to use mock and build on the oldest version you want to support? This is how EPEL packages are built for example. It is targeted at building RPMs, but you can manually use copy-in and copy-out to do other things.

8 thoughts on - Building For Older Versions

  • IMO you should really be building your app on an older CentOS version (5
    or 6). Then your binary should run everywhere, though it may sometimes require installing a -compat package.

    An alternative is to link everything statically. Not as good a solution, as it introduces security concerns.

  • The situation with memcpy is a bit different. This isn’t really a forward/backward interface compatibility issue.

    There was a patch applied to memcpy to improve performance on some architectures, but it also changed the order in which data was moved. Some programs were dependent on this and they broke with the new implementation. These programs did not conform to the non-overlapping data requirements in memcpy’s specification. Programs which did conform worked with both the new and old implementation.

    To prevent non-conforming programs from using the new version of memcpy, they tagged it with glibc-2.14. Unfortunately, this also makes conforming programs, which work with either the old or new implementation from running on systems which have older versions of glibc.

    I’ll look into mock.

  • That causes a number of other problems, when the only issue is accessing a working version of memcpy from the installed glibc.

  • can you please provide some details? I’m genuinely curious as I’ve been faced with this occasionally and the only problem I’ve encountered is having to install a few *-compat packages. thanks.

  • Building on an older version of CentOS means using older compilers and libraries. Some applications require building with more current tools.

    So you end up between a rock and a hard place. You can try to build on the older system for library compatibility, but then you have to use development tools from newer versions. Or you can build with the newer tools, and you have compatibility issues running on the older system.

  • Yeah. I know about LSB and I’ve worked with the LSB committee. Maybe it’s time I tried using it. :-)

    It does seem to be a sledge hammer to address what seems to be a minor issue.

  • Once upon a time, Michael Eager said:

    Maybe try an older base OS but with tools from a software collection add-on? That’s trickier to do with mock (I figured it out once but don’t remember now).