Calling a C++ dll method from Java using JNA and avoiding Method Name Mangling

Question

I have been going through links on StackOverflow on how to resolve the Method name mangling but did not find any solution with a real time example.

Scenario-A C++ Ex.dll file is provided by client. I need to access the Ex.dll and call the methods in the same through Java.

Restrictions- Cannot modify the Ex.dll, i can only access the same.

Issue Faced- Getting the below exception when i access the Ex.dll through JNA

Exception in thread "main" java.lang.UnsatisfiedLinkError: Error looking up function 'getCPUSpeed': The specified procedure could not be found.
at com.sun.jna.Function.<init>(Function.java:134)
at com.sun.jna.NativeLibrary.getFunction(NativeLibrary.java:336)
at com.sun.jna.NativeLibrary.getFunction(NativeLibrary.java:316)
at com.sun.jna.Library$Handler.invoke(Library.java:203)
at $Proxy0.getCPUSpeed(Unknown Source)
at cpp.java.JnaTest.main(JnaTest.java:16)

Googled a lot and found that its due to method name Mangling, but again could not find any good sample code with the solution.

This is code i used-

import com.sun.jna.Native;
class JnaTest
{

public static void main(String args[])
{
    try 
    {
        JnaInterface jInterface = (JnaInterface) Native.loadLibrary("Ex", JnaInterface.class);

        System.out.println("Calling C++ DLL method");
        System.out.println("========================");
        System.out.println("getCPUSpeed() -- "+jInterface.getCPUSpeed());

    } catch (Exception e) {
        e.printStackTrace();
    }
}
}



package cpp.java;
import com.sun.jna.Library;
public interface JnaInterface extends Library{  
public int getCPUSpeed();
}

Update 1: **************************************

Below mentioned is the actual functions i get when i browse the DBMM.dll through dependency walker-

DBMM DLL functions-

??0cDbmmInterfaceCache@@QAE@ABV0@@Z

??0cDbmmInterfaceCache@@QAE@XZ

??0cDbmmInterfaceControl@@QAE@ABV0@@Z

??0cDbmmInterfaceControl@@QAE@XZ

??0cDbmmInterfaceEcon@@QAE@ABV0@@Z

??0cDbmmInterfaceEcon@@QAE@XZ

??0cDbmmInterfaceKnob@@QAE@XZ

??0cDbmmInterfaceOutput@@QAE@ABV0@@Z

??0cDbmmInterfaceOutput@@QAE@H@Z

??0cDbmmInterfacePoolLoan@@QAE@ABV0@@Z

??0cDbmmInterfacePoolLoan@@QAE@V?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z

??0cDbmmMacroEcon@@QAE@ABV0@@Z

??0cDbmmMacroEcon@@QAE@ABVcDbmmInterfaceEcon@@_N@Z

??0cDbmmMtgBasisConstSpreadModel@@IAE@XZ

??0cDbmmMtgBasisConstSpreadModel@@QAE@ABV0@@Z

??0cDbmmMtgBasisConstSpreadModel@@QAE@PBD@Z

??0cDbmmMtgBasisModel@@QAE@ABV0@@Z

??0cDbmmMtgBasisModel@@QAE@XZ

??0cScaleFieldsSubSum@@QAE@NN@Z

??1cDbmmInterfaceCache@@QAE@XZ

??1cDbmmInterfaceControl@@QAE@XZ

??1cDbmmInterfaceEcon@@QAE@XZ

??1cDbmmInterfaceKnob@@QAE@XZ

??1cDbmmInterfaceOutput@@QAE@XZ

??1cDbmmInterfacePoolLoan@@QAE@XZ

??1cDbmmMacroEcon@@QAE@XZ

??1cDbmmMtgBasisConstSpreadModel@@UAE@XZ

??1cDbmmMtgBasisModel@@UAE@XZ

??1cScaleFieldsSubSum@@QAE@XZ

??4cDbmmInterface@@QAEAAV0@ABV0@@Z

??4cDbmmInterfaceCache@@QAEAAV0@ABV0@@Z

??4cDbmmInterfaceControl@@QAEAAV0@ABV0@@Z

??4cDbmmInterfaceEcon@@QAEAAV0@ABV0@@Z

??4cDbmmInterfaceKnob@@QAEAAV0@ABV0@@Z

??4cDbmmInterfaceOutput@@QAEAAV0@ABV0@@Z

??4cDbmmInterfacePoolLoan@@QAEAAV0@ABV0@@Z

??4cDbmmMacroEcon@@QAEAAV0@ABV0@@Z

??4cDbmmMtgBasisConstSpreadModel@@QAEAAV0@ABV0@@Z

??4cDbmmMtgBasisModel@@QAEAAV0@ABV0@@Z

??4cScaleFieldsSubSum@@QAEAAV0@ABV0@@Z

??_7cDbmmMtgBasisConstSpreadModel@@6B@

??_7cDbmmMtgBasisModel@@6B@

??_FcDbmmInterfaceOutput@@QAEXXZ

??_FcDbmmInterfacePoolLoan@@QAEXXZ

??_FcScaleFieldsSubSum@@QAEXXZ

?Add@cScaleFieldsSubSum@@QAEXNN@Z

?InitSubsum@cScaleFieldsSubSum@@QAEXNN@Z

?ReInit@cDbmmMacroEcon@@QAEX_N@Z

Not sure how can i call these functions through Java.

Appreciate if somebody could provide me a solution from Java end, with a sample code please :)

The Method Name when verified through Dependency Walker is _Java_sysInfo_getCPUSpeed@8 how can this be resolved from the Java end, i.e class JnaTest what are the changes that needs to be done to map the method name as the one shown through dependency walker. — P.D, Apr 12 '13 at 07:36

score 0 · Answer 1 · edited May 23 '17 at 12:22

0

Your function is decorated with JNI and stdcall conventions; it is not C++-mangled.

It looks like the library is a JNI library, given the Java_sysInfo_ prefix. If that is the case, you need only declare the equivalent Java-side, e.g.

// default package
public class sysInfo {
    static { System.loadLibrary("Ex"); }
    public static native int getCPUSpeed();
}

I think you'll probably find that this mapping is the correct one and that you don't need JNA.

EDIT

Given a C++ class with an arbitrary ctor input argument and method getCount():

extern "C" int getCountForName(const char* name) {
    MyCPPClass mycpp(name);
    return mycpp.getCount();
}

Compile that into a shared library, and load via JNA.

edited May 23 '17 at 12:22

Community

1
1

answered Apr 12 '13 at 12:12

technomage

9,861
2
26
40

Hi Technomage,Thanks for the reply.The above mentioned is an example i'm trying to find a solution. Updated the question with the actual methods i find when i browse the dll through Dependency walker. – P.D Apr 16 '13 at 06:20
Those *are* C++-mangled names. If they are static methods, you can call them directly, but if they are member methods you'll need to either write a wrapper which exposes simple (extern "C") functions, or use a tool like [JNAerator](http://code.google.com/p/jnaerator/) to generate more complex mappings. – technomage Apr 16 '13 at 11:05
Thanks for the reply Technomage, Can you please provide a sample code or any reference site on how to write the wrapper which exposes simple(extern "C") functions? As i'm new to C++ java integration.Meanwhile i'm looking into JNAerator. – P.D Apr 17 '13 at 06:02
@technomage Is it enough to just consider the function declarations and not their contents, when calling non- extern "C" C++ functions? – mavavilj Dec 24 '22 at 11:23
What do you mean by "contents"? For static functions, as long as you know the parameter types that should be enough, but for member functions you'll need to somehow provide a `this` pointer. – technomage Feb 13 '23 at 18:57

score 0 · Answer 2 · answered Sep 10 '13 at 18:05

0

If your building the DLL through Visual studio, you should be able to build it as a release instead of debug to fix the function names if you are not already doing this.

answered Sep 10 '13 at 18:05

Adam

186
1
6

Calling a C++ dll method from Java using JNA and avoiding Method Name Mangling

2 Answers2