[Linker error] undefined reference to `_imp__JNI_CreateJavaVM@12'

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Hi,

I am new to JNI and I have been trying to write a simple program to call Java code from C++.

I am facing problem in creating the JavaVM from C and am getting the Linker error. I have tried changing the GNU library files in dev C++ (I am using Dev c++ compiler) but no luck so far.
The JDK version is 1.6.27.

Can anybody help me and point out the error or recommend a step-by-step approach to write this program?

Here is the C code file I am trying to compile.

C++

#include <jni.h>
#include <windows.h>
 
#define PATH_SEPARATOR ';' /* define it to be ':' on Solaris */
#define USER_CLASSPATH "." /* where Prog.class is */
 
main() {
    JNIEnv *env;
    JavaVM *jvm;
    jint res;
    jclass cls;
    jmethodID mid;
    jstring jstr;
    jclass stringClass;
    jobjectArray args;
 
#ifdef JNI_VERSION_1_2
    JavaVMInitArgs vm_args;
    JavaVMOption options[1];
    options[0].optionString =
        "-Djava.class.path=" USER_CLASSPATH;
    vm_args.version = 0x00010002;
    vm_args.options = options;
    vm_args.nOptions = 1;
    vm_args.ignoreUnrecognized = JNI_TRUE;
    /* Create the Java VM */
    // this should contain the path to the JVM DLL file
    HINSTANCE hVM = LoadLibrary("C:\\Program Files\\Java\\jdk1.6.0_27\\jre6\\bin\\client\\jvm.dll");
if (hVM == NULL)
{
    DWORD dwe = GetLastError();
    return -1;
}
typedef jint	
(CALLBACK *fpCJV)(JavaVM**, void**, JavaVMInitArgs*);

fpCJV CreateJavaVM = (fpCJV)::GetProcAddress(hVM, "JNI_CreateJavaVM");
res = CreateJavaVM(&jvm, (void**)&env, &vm_args);
#else
    JDK1_1InitArgs vm_args;
    char classpath[1024];
    vm_args.version = 0x00010001;
    JNI_GetDefaultJavaVMInitArgs(&vm_args);
    /* Append USER_CLASSPATH to the default system class path */
    sprintf(classpath, "%s%c%s",
            vm_args.classpath, PATH_SEPARATOR, USER_CLASSPATH);
    vm_args.classpath = classpath;
    /* Create the Java VM */
    res = JNI_CreateJavaVM(&jvm, &env, &vm_args);
#endif /* JNI_VERSION_1_2 */

    if (res < 0) {
        fprintf(stderr, "Can't create Java VM\n");
        exit(1);
    }
    cls = (*env)->FindClass(env, "Prog");
    if (cls == NULL) {
        goto destroy;
    }

    mid = (*env)->GetStaticMethodID(env, cls, "main",
                                    "([Ljava/lang/String;)V");
    if (mid == NULL) {
        goto destroy;
    }
    jstr = (*env)->NewStringUTF(env, " from C!");
    if (jstr == NULL) {
        goto destroy;
    }
    stringClass = (*env)->FindClass(env, "java/lang/String");
    args = (*env)->NewObjectArray(env, 1, stringClass, jstr);
    if (args == NULL) {
        goto destroy;
    }
    (*env)->CallStaticVoidMethod(env, cls, mid, args);

destroy:
    if ((*env)->ExceptionOccurred(env)) {
        (*env)->ExceptionDescribe(env);
    }
    (*jvm)->DestroyJavaVM(jvm);
}

Could you please check if it gives any compilation error to you?

Posted 3-Oct-11 20:11pm

anktrive

Updated 4-Oct-11 22:50pm

Richard MacCutchan

v4

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Comments

Dalek Dave 4-Oct-11 4:54am

Edited for Readability.

4 solutions

Solution 1

See here[^] to check your code is following the correct rules. Also, make sure you have defined your JNI calls within extern "C" {} blocks, to prevent name mangling by the compiler.

Posted 3-Oct-11 22:11pm

Richard MacCutchan

Comments

Dalek Dave 4-Oct-11 4:54am

Good Link

anktrive 4-Oct-11 5:51am

Hi Richard, Thanks for the quick response.... I have used the exact same code given in the link and used Dev c++ to compile it, so it should follow the rules. In this code only I have received Linker error. I suspect it is not able to locate the java executables on my system.The environment variables on my system are:
PATH: C:\Program Files\Java\jdk1.6.0_27\bin;C:\Program Files\Java\jdk1.6.0_27\jre\bin\client
JAVA_HOME: C:\Program Files\Java\jdk1.6.0_27\bin
LD_LIBRARY_PATH= C:\Program Files\Java\jdk1.6.0_27\jre\bin\client
CLASSPATH= C:\data

Could you please let me know if any of these system variables should be defined differently?

Richard MacCutchan 4-Oct-11 7:18am

That looks OK, you should also check that the jvm.dll file is accessible in C:\Program Files\Java\jdk1.6.0_27\jre\bin\client.

anktrive 4-Oct-11 7:32am

I have already checked it since i found it as one of the possible reasons why JVM could not be created. JVM.dll is there. Is there a possibility that it is not accesible at runtime even if it is at the correct location?

Richard MacCutchan 4-Oct-11 8:04am

Not that I can think of; if you have linked it with the correct .lib file, and the dll is in the Windows path then it should all work. Unfortunately I don't have a ready made test program to try this on my system at the moment. If I get time later I may give it a go.

anktrive 5-Oct-11 1:26am

When you say linking with the correct .lib file, does it mean giving the library path for jvm.lib to C compiler or setting it as LD_LIBRARY_PATH in the environment variables?

Richard MacCutchan 5-Oct-11 3:23am

Please ignore this, see my 'proper' solution below.

Solution 2

It's customary to locate the java runtime trough settings from the registry, and then load the dll dynamically.

Have look at:
Jace[^]
Jace offers some additional features you might find interesting too.

[Update]
The _imp__ prefix indicates that you have a problem with your library - I assume you are using MinGW with Dev c++, it's been a while since I played around with it - but if I remember correctly there is a tool provided with MinGW that allows you to create *.a files for dll's based on def files ...

If you're unfamiliar with def files take a look at:
Visual C++ 2010 Express [^] - it's free too.

[Update 2]
Have you read The Java™ Native Interface[^]?

MinGW dlltool[^]

Stdcall and DLL tools of MSVC and MinGW[^]

Best regards
Espen Harlinn

Posted 3-Oct-11 22:37pm

Espen Harlinn

Updated 5-Oct-11 2:39am

v3

Comments

Richard MacCutchan 4-Oct-11 7:16am

I've used JNI quite a bit and never had to do that.

Espen Harlinn 4-Oct-11 10:24am

It's how the java.exe, Eclipse, and many other tools load the java runtime - and you don't need to have the %JAVA_HOME%\bin directory in your path.

Solution 3

I don't know why this happens BUT:
In your C code, if you replace the line:

C++

res = JNI_CreateJavaVM(&jvm, (void**)&env, &vm_args);

with

C++

// this should contain the path to the JVM DLL file
HINSTANCE hVM = LoadLibrary("C:\\Program Files (x86)\\Java\\jre6\\bin\\client\\jvm.dll");
if (hVM == NULL)
{
    DWORD dwe = GetLastError();
    return -1;
}
typedef jint	(CALLBACK *fpCJV)(JavaVM**, void**, JavaVMInitArgs*);
fpCJV CreateJavaVM = (fpCJV)::GetProcAddress(hVM, "JNI_CreateJavaVM");
res = CreateJavaVM(&jvm, (void**)&env, &vm_args);

it should work; at least it does on my system. I will continue to investigate further as time permits.

Posted 4-Oct-11 3:55am

Richard MacCutchan

Comments

Espen Harlinn 4-Oct-11 11:35am

5'ed - "HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment" contains a value called "CurrentVersion" = 1.6 - indicating that one should look at the RuntimeLib value under HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Runtime Environment\1.6 - it contains the full path to the jvm.dll, like "C:\Program Files (x86)\Java\jre6\bin\client\jvm.dll"

Richard MacCutchan 4-Oct-11 12:02pm

You are correct, of course, it's just that I have always done it like this, without recourse to the registry.

anktrive 5-Oct-11 3:41am

The following line gives a compilation error as "syntax error before ':' token "
fpCJV CreateJavaVM = (fpCJV)::GetProcAddress(hVM, "JNI_CreateJavaVM");
Am I missing any import header file?
Sorry for the dumb question but i am new to C programming as well.

Richard MacCutchan 5-Oct-11 4:11am

Did you put the typedef line before it?

anktrive 5-Oct-11 4:14am

Here is the C code file I am trying to compile.

#include <jni.h>
#include <windows.h>

#define PATH_SEPARATOR ';' /* define it to be ':' on Solaris */
#define USER_CLASSPATH "." /* where Prog.class is */

main() {
JNIEnv *env;
JavaVM *jvm;
jint res;
jclass cls;
jmethodID mid;
jstring jstr;
jclass stringClass;
jobjectArray args;

#ifdef JNI_VERSION_1_2
JavaVMInitArgs vm_args;
JavaVMOption options[1];
options[0].optionString =
"-Djava.class.path=" USER_CLASSPATH;
vm_args.version = 0x00010002;
vm_args.options = options;
vm_args.nOptions = 1;
vm_args.ignoreUnrecognized = JNI_TRUE;
/* Create the Java VM */
// this should contain the path to the JVM DLL file
HINSTANCE hVM = LoadLibrary("C:\\Program Files\\Java\\jdk1.6.0_27\\jre6\\bin\\client\\jvm.dll");
if (hVM == NULL)
{
DWORD dwe = GetLastError();
return -1;
}
typedef jint
(CALLBACK *fpCJV)(JavaVM**, void**, JavaVMInitArgs*);

fpCJV CreateJavaVM = (fpCJV)::GetProcAddress(hVM, "JNI_CreateJavaVM");
res = CreateJavaVM(&jvm, (void**)&env, &vm_args);
#else
JDK1_1InitArgs vm_args;
char classpath[1024];
vm_args.version = 0x00010001;
JNI_GetDefaultJavaVMInitArgs(&vm_args);
/* Append USER_CLASSPATH to the default system class path */
sprintf(classpath, "%s%c%s",
vm_args.classpath, PATH_SEPARATOR, USER_CLASSPATH);
vm_args.classpath = classpath;
/* Create the Java VM */
res = JNI_CreateJavaVM(&jvm, &env, &vm_args);
#endif /* JNI_VERSION_1_2 */

if (res < 0) {
fprintf(stderr, "Can't create Java VM\n");
exit(1);
}
cls = (*env)->FindClass(env, "Prog");
if (cls == NULL) {
goto destroy;
}

mid = (*env)->GetStaticMethodID(env, cls, "main",
"([Ljava/lang/String;)V");
if (mid == NULL) {
goto destroy;
}
jstr = (*env)->NewStringUTF(env, " from C!");
if (jstr == NULL) {
goto destroy;
}
stringClass = (*env)->FindClass(env, "java/lang/String");
args = (*env)->NewObjectArray(env, 1, stringClass, jstr);
if (args == NULL) {
goto destroy;
}
(*env)->CallStaticVoidMethod(env, cls, mid, args);

destroy:
if ((*env)->ExceptionOccurred(env)) {
(*env)->ExceptionDescribe(env);
}
(*jvm)->DestroyJavaVM(jvm);
}
Could you please check if it gives any compilation error to you?

anktrive 5-Oct-11 4:16am

The include directives that are missing in the above code
#include jni.h
#include windows.h

[no name] 24-Sep-12 14:17pm

Hey hi. This is sandeep.
I am also trying to do the similar kind of work you are doing, like calling a java method inside c. I have lot of errors. Can you please correct me where i am wrong.

Errors mainly in the lines
(CALLBACK *fpCJV)(JavaVM**, void**, JavaVMInitArgs*);
HINSTANCE hVM;
fpCJV CreateJavaVM;
hVM= LoadLibrary("C:\\Program Files (x86)\\Java\\jre7\\bin\\client\\jvm.dll");

This is whole code. Please somebody help me.

#include
#include
#include
#ifdef _WIN32
#define PATH_SEPARATOR ';'
#else
#define PATH_SEPARATOR ':'
#endif

int _stdcall DLLHeader (void)
{
return 1;
}
int main()
{
JavaVMOption options[1];
JNIEnv *env;
JavaVM *jvm;
JavaVMInitArgs vm_args;
long status;
jclass cls;
jmethodID mid;
jint square;
jboolean not;

options[0].optionString = "-Djava.class.path=.";
memset(&vm_args, 0, sizeof(vm_args));
vm_args.version = 0x00010002;
vm_args.options = options;
vm_args.nOptions = 1;
vm_args.ignoreUnrecognized = JNI_TRUE;
#include
#include "jni.h"
#include "jni_md.h"

typedef jint
(CALLBACK *fpCJV)(JavaVM**, void**, JavaVMInitArgs*);
// this should contain the path to the JVM DLL file
HINSTANCE hVM;
fpCJV CreateJavaVM;
hVM= LoadLibrary("C:\\Program Files (x86)\\Java\\jre7\\bin\\client\\jvm.dll");
if (hVM == NULL)
{
DWORD dwe = GetLastError();
return -1;
}

CreateJavaVM = (fpCJV)GetProcAddress(hVM, "JNI_CreateJavaVM");
status = CreateJavaVM(&jvm, (void**)&env, &vm_args);

//status = JNI_CreateJavaVM(&jvm, (void**)&env, &vm_args);

if (status != JNI_ERR)
{
cls = (*env)->FindClass(env, "TestClass");
if(cls !=0)
{ mid = (*env)->GetStaticMethodID(env, cls, "intMethod", "(I)I");
if(mid !=0)
{ square = (*env)->CallStaticIntMethod(env, cls, mid, 5);
printf("Result of intMethod: %d\n", square);
}
}

(*jvm)->DestroyJavaVM(jvm);
return 0;
}
else
return -1;
}

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Richard MacCutchan · Accepted Answer · 2011-10-04T23:28:00

My apologies but I was compiling as C++, which does not work for standard C. Modify the code between the lines #ifdef JNI_VERSION_1_2 and #else as follows:

C++

#ifdef JNI_VERSION_1_2
// definitions required to get the proc address
	HINSTANCE hVM;
	typedef jint	(CALLBACK *fpCJV)(JavaVM**, void**, JavaVMInitArgs*);

	fpCJV CreateJavaVM;
	JavaVMInitArgs vm_args;
	JavaVMOption options[1];
	options[0].optionString =
		"-Djava.class.path=" USER_CLASSPATH;
	vm_args.version = 0x00010002;
	vm_args.options = options;
	vm_args.nOptions = 1;
	vm_args.ignoreUnrecognized = JNI_TRUE;
	/* Create the Java VM */
// load the Java VM dll
	hVM = LoadLibrary("C:\\Program Files (x86)\\Java\\jre6\\bin\\client\\jvm.dll");
	if (hVM == NULL)
	{
		DWORD dwe = GetLastError();
		return -1;
	}
// get the address of the first JNI call and create the VM
	CreateJavaVM = (fpCJV)GetProcAddress(hVM, "JNI_CreateJavaVM");
	res = CreateJavaVM(&jvm, (void**)&env, &vm_args);
#else

I have added some extra comment lines preceding the code that requires changing. You may also like to consider moving to C++ which offers lots of benefits over pure C.

~~We still have the issue of why the linker cannot find the JNI_CreateJavaVM call, which I may return to as time permits, but at least this solution should allow you to continue working with JNI.~~

I finally found the time to go and look at this properly, and realised that I have mixed mode libraries on my Windows 7 system. I downloaded the 32bit JDK and now I can link and run successfully. Please check that you are using all 32 bit (from C:\Program Files (x86)\Java) or all 64bit (from C:\Program Files\Java) for your projects.

[Linker error] undefined reference to `_imp__JNI_CreateJavaVM@12'

4 solutions

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Solution 2

Solution 3

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