I try to develop a thirdparty unixODBC driver, it is a secondary development based on the original file libodbc.so.2.0.0.
so I want to rename 'libodbc.so.2.0.0' to 'libodbc.so.2.0.0_renamed'. And soft link my dynamic library file to libodbc.so.2.0.0.
But I found an issue bothering me, when I rename native file and run 'sudo ldconfig', the file named 'libodbc.so.2' automatically linked to the renamed file 'libodbc.so.2.0.0_renamed', as below:
I could not understand that:
why it occurs;
how to appropriately replace the library.
I don't have enough ackownledge about linux, so that I failed to get any keyword to search and deal with it.
Could you help me, thank you very much!
Shared objects under GNU/Linux follow a specific version naming scheme, which is known by the loader (and OS component, actually part of libc framework) to determine if a newer library is retro-compatible with some older version to which a binary was originally linked against. By adding the renamed suffix, you are violating the convention and the dynamic linking system is getting confused. You should renamed as suggested by #Bodo above.
In addition, perhaps rather than using rename, you might consider using the very versioning scheme. From GNU Build System (aka Autotools) manual, the version cheme is like it follows:
Versioning: CURRENT:REVISION:AGE
CURRENT The latest interface implemented.
REVISION The implementation number of CURRENT (read: number of bugs fixed...)
AGE The number of interfaces implemented, minus one.
The library supports all interfaces between CURRENT − AGE and CURRENT.
If you have
not changed the interface (bug fixes) CURRENT : REVISION+1 : AGE
augmented the interface (new functions) CURRENT+1 : 0 : AGE+1
broken old interface (e.g. removed functions) CURRENT+1 : 0 : 0
Therefore a possible history of your lib might be:
1:0:0 start
1:1:0 bug fix
1:2:0 bug fix
2:0:1 new function
2:1:1 bug fix
2:2:1 bug fix
3:0:0 broke api
3:1:0 bug fix
4:1:1 bug fix
5:0:0 broke api
You might, for instance, call the older and newer versions of libodbc.so.x.y.z, according to your needs. Just an idea.
Related
FUSE = Filesystem in user space recommends that distros package both a fuse2 and a fuse3 (see here) and indeed they do.
What exactly is the reason for this? Is it just that the init code in fuse3 is different?
The release notes for libfuse 3.0.0 appear comprehensive. Read below the heading 'Changes (since FUSE 2.9)'. Functions have been renamed for clarity, functions dropped and parameters tidied up. Here are a few examples from the release notes to give a flavour:
The fuse_lowlevel_new function has been renamed to
fuse_session_new and no longer interprets the --version or --help
options
fuse_loop(), fuse_loop_mt(), fuse_session_loop() and fuse_session_loop_mt() now return more detailed error codes instead of just -1. See the documentation of fuse_session_loop() for details
There are new fuse_session_unmount and fuse_session_mount
functions that should be used in the low-level API. The fuse_mount
and fuse_unmount functions should be used with the high-level API
only
The fuse_invalidate function has been removed
Installing libfuse2 alongside libfuse3 allows applications using libfuse2 to keep working without needing to be updated straight away.
What happend:
I'm now working on a linux side-by-side installation issue since rpm no longer support to install the 32-bit and 64-bit same name packages on a machine at the same time. So I need to change the name of the 32-bit package from xxx.i386.rpm to xxx-32bit.i386.rpm. For supporting the upgrade of this package, I should provide the old package name: xxx in the spec file.
Problem:
I've looked into the pages of rpm.org looking for whether we can specify the version which we provided in the spec file like:
Provides: xxx = 16.0
I've done some test and it seems to work. But I can't find any offical explanation.
Does anyone else know the properly behaviour if I specified the provides package version in the Provides.
I'm putting aside that multilib is still supported by RPM (and I'm puzzled why are you doing that). But when i focus on that spec problem.
You have it nearly correct. Just omit that percent sign. Correct is:
Provides: xxx = 16.0
Note that the "16.0" should be just version. While it technically can be version-release, this will make you trouble some time later.
And if you want to provide really clean upgrade path, you should put there Obsolete too. See https://docs.fedoraproject.org/en-US/packaging-guidelines/#renaming-or-replacing-existing-packages
As far as I understand, "2" in "/lib/ld-linux.so.2" changes very rarely. There are old programs that can't work with new library and new programs that can't work with the old library. But they both refer to /lib/ld-linux.so.2, preventing installing both libraries.
BTW what are that version 'GLIBC_2.17' not found things? Why version is not in soname, but somewhere else?
Whenever a library is changed in a way that old programs do not work with the new version of the library this number is chaned. If old programs will still work with the newer library (and programs needing the new version will not cause a crash with the old library) there is no need to change the number because you can simply install the latest version of the library.
As far as I understand the "2" (it was "1" ten years ago) should not change any longer. The reason is simple:
The first version of "ld-linux.so.2" was written in a way that any version of "ld-linux.so.2" should work with any program using this file - maybe printing an error message when an older version of "ld-linux.so.2" is used.
This means: It is never necessary to install two different "ld-linux.so.2" files but it is enough to install the latest version of this file. You should not simply overwrite this file because it comes as a bundle with other files (e.g. "libc.so.6") that must have the same version.
In the "2" version of the loader .so files may contain a table of version numbers supported. So "libc.so.6", version GLIBC_2.16, may contain the information that "GLIBC_2.15" is also supported by this version of the library. (New versions should be backward compatible so this should be the case.)
Programs may contain a list of versions required (for example: a program requires libc.so.6 version "GLIBC_2.17"). The loader (ld-linux.so.2) checks if the library supports the version that is required by the program and refuses starting the program if not. In this case the error message form your question is printed by the loader.
I have a dynamic library that changes name across major versions i.e. version 3 was named lib3 and version 4 is named lib4, and so on.
I need to provide a shim lib3 that will allow an old application to use the new library in a transparent way, and most of the exported functions did not change across versions, so a forwarding DLL looks pretty good for the task on Windows.
Is there something equivalent on Linux/Unix?
The Linux equlivalent is rather easy. You can just use a symbolic link. For example, lib4 is the new library version, then you can create the following symbolic link:
ln -s lib4 lib3
Now, every time a program will need lib3 will automatically load lib4 as long as the interface
exported by the new version is equal to the old version, the program will not notice the difference.
I hope this helps. Let me know if you need more info.
Im using a market data source implementation that contains .so.0 files. However these are 'soft links' to actual .so.0.0.0 files. Why is this done?
When I try to copy these .so.0 links, it ends up copying an exact replica of the .so.0.0.0 file but with a .so.0 prefix.
Added comment:
so I have a libfoo.so file, and it is being accessed by java through jni. This libfoo.so file is actually a soft link that points to libfoo.so.0.0.0 What happens if I don't have libfoo.so. How does java/or any other compiled code, figure out that libfoo.so.0.0.0 if the shared object to use?
This is so programs can bind to either any version of libfoo that has the same interface (I want the latest updates to libfoo), or bind to a specific version (I want stability and only the exact version I tested against).
The .0 and .0.0.0 files exist so that versioning can happen:
foo.0 represents the .0 version of a library. All .0 versions of the library will use the same interface, but there may be different implementations. (Hopefully, the later implementations will have fewer bugs than the earlier ones.)
foo.0.0.0 represents a specific implementation of the .0 version.
It's not useful, now, to have the soft-link. But here's what could happen:
The programmer of foo finds a bug in his library. He releases foo.0.0.1. And foo.0 now links to foo.0.0.1. Then two things happen:
All files that link to foo.0 will automatically update to foo.0.0.1.
All files that link to foo.0.0.0 will continue to use the old foo.0.0.0