java.lang.Error: Invalid memory access while using JNA call

[Sanjeev]

I am using jna.jar to call native API(dll) that is written in c/c++.
One of the call is throwing 'Invalid memory access'.

A structre written in C is
typedef struct {
void *instance;
const mcd_core_con_info_st *core_con_info;
} mcd_core_st;


The equivalent structre in java I have written is.

public class MCDCore extends Structure {
public static class ByValue extends MCDCore implements Structure.ByValue {}

public static class ByReference extends MCDCore implements Structure.ByReference {}

public Pointer instance = new Pointer(-1);

public MCDCoreConnectionInfo.ByReference coreConInfo = null;
}

Where MCDCoreConnectionInfo is another structure and I guess this structure is correct because I am successfully able to make calls using this structure.

C methods definition
mcd_open_core_f(const mcd_core_con_info_st *core_con_info, mcd_core_st **core);

equivalent java method.

public mcd_open_core_f(MCDCoreConnectionInfo core_con_info, Pointer core);

Another C method

mcd_qry_reg_map_f(const mcd_core_st *core, int reg_group_id, int start_index, int *num_regs, mcd_register_info_st *reg_info);

equvalent Java method

public void mcd_qry_reg_map_f(MCDCore core, int regGroupId, int i,IntByReference numRegs, MCDRegisterInfo regInfo);

Now working C code.
mcd_core_st *core;
mcd->mcd_open_core_f(&core_con_info_core, &core);

mcd_register_info_st core_ip_reg;
int reg_group_id = 0;
int num_regs = 0;
mcd->mcd_qry_reg_map_f(core, reg_group_id, 0, &num_regs, 0);

equvalent code written in java







Now when I make call in C++.

mcd_core_st *core;
mcd->mcd_open_core_f(&core_con_info_core, &core);

Equvalent code in java

MCDCore core = new MCDCore();
mcdAPI.mcd_open_core_f(coreInfo, core.getPointer());
// this is successfull call.
MCDRegisterInfo regInfo = new MCDRegisterInfo();
IntByReference num_regs = new IntByReference(0);
int reg_group_id = 0;
mcdAPI.mcd_qry_reg_map_f(core, reg_group_id, reg_group_id,num_regs, null);
// this line gives following error.

Exception in thread "main" java.lang.Error: Invalid memory access
at com.sun.jna.Function.invokeInt(Native Method)
at com.sun.jna.Function.invoke(Function.java:344)
at com.sun.jna.Function.invoke(Function.java:276)
at com.sun.jna.Library$Handler.invoke(Library.java:21 6)
at $Proxy0.mcd_qry_reg_map_f(Unknown Source)
at com.kpit.mcd.jna.Main.main(Main.java:104)

Please suggest me the probable reason and solution for error 'Invalid memory access'.

-Sanjeev

[Sanjeev]

I got the solution correct mapping of C method
mcd_open_core_f(const mcd_core_con_info_st *core_con_info, mcd_core_st **core);
in java
mcd_open_core_f(MCDCoreConnectionInfo core_con_info, PointerByReference cores);