Invalid memory access when using JNA in JAVA

Question

I am trying to use JNA to call the function in mySMS.DLL to read SMS from a device. The sms details will be read into sMessage, sFrom and sTime. However, I get the below error.

No idea on what causing the error. Please help. Many thanks.

C:\Users\Chi\Desktop\SMS_Pool\install\sms.dll\Mysms.dll>set classpath=.;C:\Program Files (x86)\Java\jre7\lib\*
C:\Users\Chi\Desktop\SMS_Pool\install\sms.dll\Mysms.dll>"C:\Program Files (x86)\Java\jre7\bin\java" SMSTest
Exception in thread "main" java.lang.Error: Invalid memory access
    at com.sun.jna.Native.invokeInt(Native Method)
    at com.sun.jna.Function.invoke(Function.java:371)
    at com.sun.jna.Function.invoke(Function.java:315)
    at com.sun.jna.Library$Handler.invoke(Library.java:212)
    at com.sun.proxy.$Proxy0.ReadSms(Unknown Source)
    at SMSTest.main(SMSTest.java:35)

API file for the DLL:

_declspec(dllexport) BOOL _stdcall ReadSms(int comport, int baud, int nIndex, char* sMessage, char* sFrom, char* sTime, BOOL bDel);

Java Code:

import com.sun.jna.Library;  
import com.sun.jna.Native;  
import com.sun.jna.Platform;  

public class SMSTest {  
    public interface CLibrary extends Library {  
        CLibrary INSTANCE = (CLibrary) Native.loadLibrary(  Platform.isWindows() ? "Mysms" : "c", CLibrary.class);  
        boolean ReadSms(int comport, int baud, int nIndex, String sMessage, String sFrom, String sTime, boolean bDel);
    }  

public static void main(String[] args) {  
try{
  String a= new String();
  String b= new String();
  String c = new String();
  System.out.println(CLibrary.INSTANCE.ReadSms(6,115200, 1, a,b,c,false));

}catch (Exception e){
}
}   
}

Check the native code, such issues generally stem out of them — mprabhat
– mprabhat, Commented Nov 27, 2014 at 9:49

technomage · Accepted Answer · 2016-04-07 21:15:58Z

2

Notice the _stdcall in your native declaration? That's an indication that your JNA interface needs to implement the StdCallLibrary interface to ensure that it uses the proper calling convention.

edited Apr 7, 2016 at 21:15

answered Nov 28, 2014 at 13:32

technomage

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