wrong soname of shared library loaded at runtime Ubuntu

eclipse-cdt, linux, shared-libraries, ubuntu

Solution

I can build the project. The problem is the dynamic linker keeps searching for libjpeg.so.9 and throwing

'error while loading shared libraries: libjpeg.so.9: ... No such file ...

You need to understand a couple of things:

- A shared library may have `SONAME` dynamic tag (visible with `readelf -d foo.so | grep SONAME`).

- If an executable is linked against such a library, the `SONAME` is recorded as a `NEEDED` dynamic tag (in the executable), regardless of what the library itself is called. That is, you can name the library `foo.so`, `foo.so.1234`, or anything else. IF the library has `SONAME` of `libbar.so.7`, then the executable will require `libbar.so.7`, no matter what [1].

On to your problem. Your executable fails to load `libjpeg.so.9`, therefor we conclude that it is being linked (at build time) with a shared library which has `SONAME: libjpeg.so.9`.

I deleted all libjpeg.* and installed libjpeg.so.62

You must not have deleted the libjpeg.so that is used at executable build time (which is somewhere other than `/usr/local/lib`). That library still has `SONAME: libjpeg.so.9`, and is causing you grief.

You can find out which libraries are being used at link time by passing `-Wl,-t` flag on the link line.

[1] Not strictly true: if the executable doesn't need any symbols from `foo.so`, and if `--as-needed` linker option is in effect, then `NEEDED: libbar.so.7` will not be recorded after all.

Update:

I have also check ldd executable and it returns libjpeg.so.62

This means that the executable that you run `ldd` on is correct, but the executable that actually run is not, and they must be different executables.

Update 2:

You're right. ldd executable shows both libjpeg.so.62 and libjpeg.so.9 are included

Actually, no, I wasn't. But I will be right this time.

What's happening is that your executable correctly records `NEEDED: libjpeg.so.62` (you can verify this with the following command: `readelf -d /path/to/exe | grep 'NEEDED.*libjpeg'`).

But you also have some other shared library (one of the ones listed in `ldd` output), which has not been rebuilt, and still has a dependency on `libjpeg.so.9`.

You can find that library by running `readelf -d /path/to/libXXX.so | grep 'NEEDED.*libjpeg\.so\.9'` on all libraries listed in `ldd` output.

Once you find it, you'll have to rebuild it so it also depends on `libjpeg.so.62`.

Problem

Original source