mlogagent_Breakpoint.c

// Called when a breakpoint is hit.
void JNICALL BreakpointCallback(jvmtiEnv *jvmti_env, JNIEnv *jni, jthread thread, jmethodID method, jlocation location) {
  // Get hold of the parameter. In this example, we just get the first parameter.
  // Which parameter is first depends on whether this is a static or instance method. 
  // For instance methods, the first parameter is a synthetic parameter representing
  // the current instance of the class. So here, we get the first "real" parameter.
  int parameterPos = 1;
  
  jobject the_parameter;
  assert(JVMTI_ERROR_NONE == (*jvmti_env)->GetLocalObject(jvmti_env, thread, 0, parameterPos, &the_parameter));
  
  // TODO: something that displays the parameter... See the full code for details.
  
  // Show a simplified stack trace.
  jvmtiFrameInfo frames[8];
  jint count;
  jvmtiError err;

  err = (*jvmti_env)->GetStackTrace(jvmti_env, thread, 0, 8, frames, &count);
  if (err == JVMTI_ERROR_NONE && count >= 1) {
    char *methodName;
    // fout is the output log file
    fprintf(fout, "  trace: ");
    for (int i = 0; i < count; i++) {
      err = (*jvmti_env)->GetMethodName(jvmti_env, frames[i].method, &methodName, NULL, NULL);
      if (err == JVMTI_ERROR_NONE) {
        fprintf(fout, "<- %s", methodName);
      }
    }
    fprintf(fout, "\n");
  }

  fflush(fout);
}