CODEWITHSUNDEEP
javalinuxopencvdebian
Firzen
Firzen

Reputation: 2094

Can't load OpenCV on Linux - undefined symbol error

So I would like to play with OpenCV little bit. My test project is in Java (OS is Debian Linux 8.4), and I have followed this tutorial to build OpenCV: https://opencv-java-tutorials.readthedocs.io/en/latest/01-installing-opencv-for-java.html

After fixing few issues, I was able to successfully build OpenCV jar and so file. There were no errors or warnings during the build. I have put opencv-400.jar and libopencv_java400.so into lib subfolder of my project. Added the jar file to build path in Eclipse, and put correct path to so file in Eclipse's Build Configurations.

My project has just a Main class which is a sample I found in OpenCV's sources, so nothing complicated:

import org.opencv.core.Core;
import org.opencv.core.CvType;
import org.opencv.core.Mat;

public class Main {

    public static void main(String[] args) {
        System.out.println("Welcome to OpenCV " + Core.VERSION);
        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);
        Mat m  = Mat.eye(3, 3, CvType.CV_8UC1);
        System.out.println("m = " + m.dump());
    }
}

It all looks that it should be working fine, but when I run the project, I see this exception:

Exception in thread "main" java.lang.UnsatisfiedLinkError: /home/firzen/ownCloud/develop/java/workspace/CVExperiments/lib/libopencv_java400.so: /home/firzen/ownCloud/develop/java/workspace/CVExperiments/lib/libopencv_java400.so: undefined symbol: _ZNK6google8protobuf8internal12MapFieldBase28SpaceUsedExcludingSelfNoLockEv
at java.lang.ClassLoader$NativeLibrary.load(Native Method)
at java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1938)
at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1854)
at java.lang.Runtime.loadLibrary0(Runtime.java:870)
at java.lang.System.loadLibrary(System.java:1122)
at Main.main(Main.java:9)

And this part of exception is really making me worried:

/home/firzen/ownCloud/develop/java/workspace/CVExperiments/lib/libopencv_java400.so: undefined symbol: _ZNK6google8protobuf8internal12MapFieldBase28SpaceUsedExcludingSelfNoLockEv

It almost seems to me that there is something wrong with that libopencv_java400.so file. Am I right? Or do I need some another files to make it work? I have build OpenCV as Debug, so that so file has 135 MiB, but that shouldn't be a problem I think.

I will be thankful for any ideas!

Upvotes: 0

Views: 362

Answers (1)

Florian Echtler
Florian Echtler

Reputation: 2503

That error means that your system does not have a suitable protobuf library installed. You might give sudo apt install libprotobuf10 a try, although I can't guarantee that will help.

Alternatively, you can also run ldd /home/firzen/ownCloud/develop/java/workspace/CVExperiments/lib/libopencv_java400.so, which will show you all libraries OpenCV tries to import - perhaps Protobuf has actually been built along with OpenCV, but is just not installed.

Upvotes: 1

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