difference between .so.0 and .so.0.0.0 files.

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linux

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+1 Q:

difference between .so.0 and .so.0.0.0 files.

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?

+6 A:

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).

Paul Betts 2010-01-05 03:14:03

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.0.0.0What 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?

2010-01-05 03:31:07

Read the `ld` man page, if on Linux.

Robert Munteanu 2010-01-05 16:00:30

If you have libfoo.so.0.0.0 you should always have libfoo.so.0 and libfoo.so, this is part of how libtool works; if it doesn't exist, they're generating the libraries wrong

Paul Betts 2010-01-05 23:15:05

+2 A:

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

Chip Uni 2010-01-05 03:41:24

Extend this a few levels further and you can require an exact version match by linking against `libfoo.0.0.0` or any matching interface version with `libfoo.0` or any version at all with `libfoo`.

D.Shawley 2010-01-05 03:46:34

Apologise for the basic question, but how is this linking specified. How can I specify that jni should use libfoo.so and not libfoo.so.0.0.0?

2010-01-05 05:04:06

Hihi, coder zambesi. Sadly, Java documents are not much help: http://java.sun.com/j2se/1.5.0/docs/api/java/lang/System.html#loadLibrary(java.lang.String) says "The manner in which a library name is mapped to the actual system library is system dependent." There might be some help at http://stackoverflow.com/questions/1010503/how-to-debug-a-java-system-loadlibrary-error-in-linux Good luck.

Chip Uni 2010-01-05 05:20:30

I struggled to understand this topic for a while; here's a good link that helped me make sense of it.

gareth_bowles 2010-01-05 15:57:33

ansaurus

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difference between .so.0 and .so.0.0.0 files.

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