If you pass 0 to printTrace, it will print the stack trace of a null

pointer exception.  This dramatically simplifies debugging in GDB:

p vm::printTrace(t, 0)

makefile

@@ -225,7 +225,7 @@ $(jni-objects): $(bld)/%.o: $(classpath)/%.cpp
 
 $(jni-library): $(jni-objects)
 	@echo "linking $(@)"
-	$(cc) $(lflags) $(shared) $(^) -o $(@)
+	$(cc) $(lflags) $(shared) $(^) -o $(@) -lssl -lcrypto
 
 $(executable): $(interpreter-objects) $(stdcpp-objects)
 	@echo "linking $(@)"

src/machine.cpp

@@ -2605,6 +2605,11 @@ collect(Thread* t, Heap::CollectionType type)
 void
 printTrace(Thread* t, object exception)
 {
+  if (exception == 0) {
+    exception = makeNullPointerException(t, 0,
+					 makeTrace(t, t->m->processor->frameStart(t)),
+					 0);
+  }
   for (object e = exception; e; e = throwableCauseUnsafe(t, e)) {
     if (e != exception) {
       fprintf(stderr, "caused by: ");