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2391 :: Calling Nim compiled to dll from Java programs?

• alexsad (orginal) [2016-07-19T14:01:36+02:00] view original

  Tried anybody do like here: Java programming with JNI

  But compiled a dll from Nim? Does exist an example?

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• yglukhov (orginal) [2016-07-19T14:22:02+02:00] view original

  Not sure if I can answer your question, but jnim allows bridging to java in a nice automagical way.

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• alexsad (orginal) [2016-07-19T14:29:31+02:00] view original

  Thanks, but I think jnim using as run Java programm on JVM from Nim

  but I need run C code (wrote on Nim and compled to dll) from Java.

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• jangko (orginal) [2016-07-20T08:36:41+02:00] view original

  You can get the source code here. There are 5 files.

  how to build sample code:

  
  javac Sample1.java
  
  javah -classpath . Sample1
  
  nim c --app:lib --passL:"-static-libgcc" --passL:"-Wl,--kill-at" Sample1
  Run

  You can omit -static-libgcc part, but you must use "-Wl,--kill-at" to remove '@' from exported symbol name.

  don't forget to include jni_export in all your project files that uses jni.nim(don't import it, use include)

  and finally, run the java vm:

  
  java Sample1
  Run

  EDIT: beware: if there exist more than one dll plugin written in Nim, please use compiler switch "-d:useNimRtl", (I never tested it before, but the documentation says like that)

  EDIT: The Sample code provided are written in C style. if you want to try C++ style, please read Playing with CPP VTABLE from Nim

  avoid using proc with va_list too, Nim don't have proper support for this C feature(I don't have time to explore/experiment with va_list in Nim yet)

  tested with:

  javac 1.7.0_79

  java version "1.7.0_79" Java(TM) SE Runtime Environment (build 1.7.0_79-b15) Java HotSpot(TM) 64-Bit Server VM (build 24.79-b02, mixed mode)

  gcc version 5.3.0 (GCC) Target: x86_64-w64-mingw32 Thread model: win32

  Nim Compiler Version 0.14.3 (2016-06-15) [Windows: amd64]

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• vega (orginal) [2016-07-20T09:42:10+02:00] view original

  @alexsad, you can do it using low level bindings (jnim.private.jni_wrapper) from jnim library for now, but it's no good. I'll make high level API for that ASAP.

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• alexsad (orginal) [2016-07-20T13:06:45+02:00] view original

  Thanks all!

  @jangko, I tried your code. It works.

  But it exist one issue if I manipulate with 'cap' variable in proc Java_Sample1_stringMethod: for example cap.add("test")

  and in JAVA for(int i=0; i<1000; i++){ text = sample.stringMethod("JAVA"+i); }

  then I get:

  A fatal error has been detected by the Java Runtime Environment:

  EXCEPTION_ACCESS_VIOLATION (0xc0000005)

  Because nim's GC does it.

  ---

  I found a solution: in the Sample1.nim at start

  GC_disable()
  Run

  and later somewhere run proc with:

  GC_enable()
  GC_fullCollect()
  GC_disable()
  Run

  or does exist better solution?

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• jangko (orginal) [2016-07-21T07:29:29+02:00] view original

  I didn't encounter the problem you've mentioned. I also increase the upper limit of for loop to 100.000 and everything still fine. I manipulate the cap variable here and there and still ok. What exactly you've done?

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• alexsad (orginal) [2016-07-21T10:20:56+02:00] view original

  What have I changed: in Sample1.java main function now is:

  public static void main(String[] args) {
      System.loadLibrary("Sample1");
      Sample1 sample = new Sample1();
      int     square = sample.intMethod(5);
      boolean bool   = sample.booleanMethod(true);
      String text	   = "";
          
          for(int i=0; i<1000; i++){
                  text   = sample.stringMethod("JAVA"+i);
          }
      
      int     sum    = sample.intArrayMethod(new int[]{1,1,2,3,5,8,13} );
      
      System.out.println("intMethod: " + square);
      System.out.println("booleanMethod: " + bool);
      System.out.println("stringMethod: " + text);
      System.out.println("intArrayMethod: " + sum);
    }
  Run

  in Sample1.nim proc Java_Sample1_stringMethod now is:

  proc Java_Sample1_stringMethod(env: ptr JNIEnv, obj: jobject, input: jstring): jstring {.JNIEXPORT.} =
    
    var isCopy: jboolean
    var str = env[].GetStringUTFChars(env, input, isCopy)
    var cap = $str
    
    cap.add("test")
    
    
    env[].ReleaseStringUTFChars(env, input, str)
    result = env[].NewStringUTF(env, cap)
  Run

  Then I get EXCEPTION_ACCESS_VIOLATION (0xc0000005)

  tested with:

  javac 1.8.0_20

  java version "1.8.0_25" Java(TM) SE Runtime Environment (build 1.8.0_25-b18) Java HotSpot(TM) 64-Bit Server VM (build 25.25-b02, mixed mode)

  gcc (x86_64-posix-seh-rev0, Built by MinGW-W64 project) 5.3.0

  Nim Compiler Version 0.14.3 (2016-07-13) [Windows: amd64]

  Thanks...

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• jangko (orginal) [2016-07-21T13:48:37+02:00] view original

  Now I can reproduce the error too. Very interesting, this code below works, maybe someone else can explain this phenomenon

  
  cap.add("test")
  var tmp = cap
  env[].ReleaseStringUTFChars(env, input, str)
  result = env[].NewStringUTF(env, tmp)
  Run

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