CODEWITHSUNDEEP
javacfunctionjava-native-interfaceexternal
Aurelien Montmejat
Aurelien Montmejat

Reputation: 132

JNI calling a C function calling an other function in an other file

I have a problem calling a C function using an other C function from an other .c file from my Java JNI (don't mind some french words in my code, thank you). The code in C works fine.

Here are the two lines I use to compile my libraries. I am compiling my first library with the function that I use in my second library. Tell me if I am doing it wrong to be able to do this :

gcc -fPIC -shared -I"$$JAVA_HOME/include" -I"$$JAVA_HOME/include/linux" -o Libraries/libfilemot.so ../IndexationTexte/fileMot.c gcc -fPIC -shared -I"$$JAVA_HOME/include" -I"$$JAVA_HOME/include/linux" ../IndexationTexte/indexationV1.c -L./Libraries/ -l:libfilemot.so -o Libraries/libindexation.so

In my Java class, I have this :

public class MoteurDeRecherche {

static {
    try {
        System.load("/home/aurelien/Documents/Projects/Projet_fil_rouge/noyau_c/JNI/Libraries/libfilemot.so");
        System.load("/home/aurelien/Documents/Projects/Projet_fil_rouge/noyau_c/JNI/Libraries/libindexation.so");
    }
    catch(UnsatisfiedLinkError e) {
        System.out.println("Erreur de chargement des librairies :\n" + e);
        System.exit(1);
    }
}

public static native void indexationTexte();

public static void main(String args[]) {
    MoteurDeRecherche.indexationTexte();
}

}

But I get this error coming from my library that compiles successfully :

Erreur de chargement des librairies :
java.lang.UnsatisfiedLinkError: /home/aurelien/Documents/Projects/Projet_fil_rouge/noyau_c/JNI/Libraries/libindexation.so: libfilemot.so: cannot open shared object file: No such file or directory

Don't hesitate if you want more information. Thank you again.

Upvotes: 0

Views: 570

Answers (2)

Aurelien Montmejat
Aurelien Montmejat

Reputation: 132

So I finally found why, this is not the way to use multiple functions from multiple files. You simply have to put all of the files you need in the gcc command. I don't know why I tried to make a library for one file dependent from an other library for an other file. Here is the command for my project :

gcc -fPIC -shared -I"$$JAVA_HOME/include" -I"$$JAVA_HOME/include/linux" ../IndexationTexte/indexationV1.c ../IndexationTexte/fileMot.c -o Libraries/libindexation.so

For a more generic approach, if you have :

file1.c :

#include "file2.c"
void function1()
{
    function2();
}

file2.c :

void function2()
{
    printf("hey from an other file");
}

You have to simply compile your project like this :

gcc -fPIC -shared -I"$$JAVA_HOME/include" -I"$$JAVA_HOME/include/linux" file1.C file2.c -o libmylibrary.so

Upvotes: 0

Elliott Frisch
Elliott Frisch

Reputation: 201447

The native linker can't find your shared object. Add the folder with your so to your LD_LIBRARY_PATH.

export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:Libraries/

Alternatively, you can add that to your local libraries folder (usually /usr/local/lib) and rerun ldconfig.

Upvotes: 1

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