jni getFields 'repeated allocation of very large block'

I try to get from a C++ program, with JNI, the list of fields of a
class, the goal being to get some reflection information on the C++
side, with this program:

int main( int argC, const char ** argV )
{
    JavaVM *jvm;
    JNIEnv *pEnv;
    JavaVMInitArgs vm_args;
    vm_args.version = JNI_VERSION_1_2;
    vm_args.nOptions = 0;
    vm_args.ignoreUnrecognized = true;

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

    jclass tstClass = pEnv->FindClass("MyClass");

    jmethodID initId = pEnv->GetMethodID(tstClass,"<init>","()V");

    jobject tstObjct = pEnv->NewObject(tstClass, initId );

    jclass jlClss = pEnv->FindClass("java/lang/Class");

    jmethodID getFlds = pEnv->GetMethodID(jlClss, "getFields", "()
[Ljava/lang/reflect/Field;");

/// 'Repeated allocation' starts from here...
    jobjectArray fields = (jobjectArray)pEnv-


  ...
    jvm->DestroyJavaVM();
};

.... and this class :
class MyClass {
    public String Nam = null;
    public int Num = 0;

    public MyClass() {
        this("Alex", 123);
    }
}

.... and I get this output after GetMethodId("getFields"):

GC Warning: Repeated allocation of very large block (appr. size
512000):
        May lead to memory leak and poor performance.
GC Warning: Repeated allocation of very large block (appr. size
512000):
        May lead to memory leak and poor performance.
.... etc ... (Endless)

I checked all returned values of JNI functions, they are fine.
gcj 4.2.2
gcc 4.2.2

Any idea, please ? Thanks.