progress towards thread support

This includes support for using the least significant bits of the class
pointer to indicate object state, which we'll use to indicate the
presence of a monitor pointer, among other things.

classpath/TestExceptions.java

@@ -5,7 +5,9 @@ public class TestExceptions {
   }
 
   private static void moreDangerous() {
-    evenMoreDangerous();
+    //    synchronized (TestExceptions.class) {
+      evenMoreDangerous();
+      //    }
   }
 
   private static void dangerous() {

classpath/TestGC.java

@@ -1,4 +1,4 @@
-public class Test {
+public class TestGC {
 
   private static void small() {
     for (int i = 0; i < 1024; ++i) {

makefile

@@ -127,7 +127,7 @@ fast-cflags = $(fast) $(cflags)
 classpath-sources = $(shell find $(classpath)/java -name '*.java')
 classpath-classes = $(call java-classes,$(classpath-sources),$(classpath))
 
-input = $(bld)/classes/TestExceptions.class
+input = $(bld)/classes/Test.class
 input-depends = \
 	$(classpath-classes) \
 	$(jni-library)

src/common.h

@@ -26,6 +26,9 @@ typedef void* object;
 const unsigned BytesPerWord = sizeof(uintptr_t);
 const unsigned BitsPerWord = BytesPerWord * 8;
 
+const uintptr_t PointerMask
+= ((~static_cast<uintptr_t>(0)) / BytesPerWord) * BytesPerWord;
+
 const unsigned LikelyPageSizeInBytes = 4 * 1024;
 
 inline unsigned
@@ -109,6 +112,13 @@ cast(object p, unsigned offset)
   return *reinterpret_cast<T*>(static_cast<uint8_t*>(p) + offset);
 }
 
+template <class T>
+inline T*
+mask(T* p)
+{
+  return reinterpret_cast<T*>(reinterpret_cast<uintptr_t>(p) & PointerMask);
+}
+
 }
 
 #endif//COMMON_H

src/heap.cpp

@@ -26,6 +26,32 @@ System* system(Context*);
 void NO_RETURN abort(Context*);
 void assert(Context*, bool);
 
+inline object
+get(object o, unsigned offsetInWords)
+{
+  return mask(cast<object>(o, offsetInWords * BytesPerWord));
+}
+
+inline object*
+getp(object o, unsigned offsetInWords)
+{
+  return &cast<object>(o, offsetInWords * BytesPerWord);
+}
+
+inline void
+set(object* o, object value)
+{
+  *o = reinterpret_cast<object>
+    (reinterpret_cast<uintptr_t>(value)
+     | reinterpret_cast<uintptr_t>(*o) & (~PointerMask));
+}
+
+inline void
+set(object o, unsigned offsetInWords, object value)
+{
+  set(getp(o, offsetInWords), value);
+}
+
 class Segment {
  public:
   class Map {
@@ -662,7 +688,7 @@ fresh(Context* c, object o)
 inline bool
 wasCollected(Context* c, object o)
 {
-  return o and (not fresh(c, o)) and fresh(c, cast<object>(o, 0));
+  return o and (not fresh(c, o)) and fresh(c, get(o, 0));
 }
 
 inline object
@@ -779,55 +805,55 @@ copy(Context* c, object o)
 }
 
 object
-update3(Context* c, object* p, bool* needsVisit)
+update3(Context* c, object o, bool* needsVisit)
 {
-  if (wasCollected(c, *p)) {
+  if (wasCollected(c, o)) {
     *needsVisit = false;
-    return follow(c, *p);
+    return follow(c, o);
   } else {
     *needsVisit = true;
-    return copy(c, *p);
+    return copy(c, o);
   }
 }
 
 object
-update2(Context* c, object* p, bool* needsVisit)
+update2(Context* c, object o, bool* needsVisit)
 {
   switch (c->mode) {
   case MinorCollection:
   case OverflowCollection:
-    if (c->gen2.contains(*p)) {
+    if (c->gen2.contains(o)) {
       *needsVisit = false;
-      return *p;
+      return o;
     }
     break;
     
   case Gen2Collection:
-    if (c->gen2.contains(*p)) {
+    if (c->gen2.contains(o)) {
-      return update3(c, p, needsVisit);
+      return update3(c, o, needsVisit);
     } else {
-      assert(c, c->nextGen1.contains(*p) or c->nextGen2.contains(*p));
+      assert(c, c->nextGen1.contains(o) or c->nextGen2.contains(o));
 
       *needsVisit = false;
-      return *p;
+      return o;
     }
     break;
 
   default: break;
   }
 
-  return update3(c, p, needsVisit);
+  return update3(c, o, needsVisit);
 }
 
 object
 update(Context* c, object* p, bool* needsVisit)
 {
-  if (*p == 0) {
+  if (mask(*p) == 0) {
     *needsVisit = false;
-    return *p;
+    return 0;
   }
 
-  object r = update2(c, p, needsVisit);
+  object r = update2(c, mask(*p), needsVisit);
 
   // update heap map.
   if (r) {
@@ -956,22 +982,22 @@ bitsetNext(Context* c, uintptr_t* p)
 }
 
 void
-collect(Context* c, void** p)
+collect(Context* c, object* p)
 {
-  object original = *p;
+  object original = mask(*p);
   object parent = 0;
   
   if (Debug) {
     fprintf(stderr, "update %p (%s) at %p (%s)\n",
-            *p, segment(c, *p), p, segment(c, p));
+            mask(*p), segment(c, *p), p, segment(c, p));
   }
 
   bool needsVisit;
-  *p = update(c, p, &needsVisit);
+  set(p, update(c, mask(p), &needsVisit));
 
   if (Debug) {
     fprintf(stderr, "  result: %p (%s) (visit? %d)\n",
-           *p,  segment(c, *p), needsVisit);
+            mask(*p), segment(c, *p), needsVisit);
   }
 
   if (not needsVisit) return;
@@ -995,17 +1021,16 @@ collect(Context* c, void** p)
       virtual bool visit(unsigned offset) {
         if (Debug) {
           fprintf(stderr, "  update %p (%s) at %p - offset %d from %p (%s)\n",
-                  cast<object>(copy, offset * BytesPerWord),
+                  get(copy, offset),
-                  segment(c, cast<object>(copy, offset * BytesPerWord)),
+                  segment(c, get(copy, offset)),
-                  &cast<object>(copy, offset * BytesPerWord),
+                  getp(copy, offset),
                   offset,
                   copy,
                   segment(c, copy));
         }
 
         bool needsVisit;
-        object childCopy = update
+        object childCopy = update(c, getp(copy, offset), &needsVisit);
-          (c, &cast<object>(copy, offset * BytesPerWord), &needsVisit);
         
         if (Debug) {
           fprintf(stderr, "    result: %p (%s) (visit? %d)\n",
@@ -1027,7 +1052,7 @@ collect(Context* c, void** p)
             second = offset;
           }
         } else {
-          cast<object>(copy, offset * BytesPerWord) = childCopy;
+          set(copy, offset, childCopy);
         }
 
         if (visits > 1 and total > 2 and (second or needsVisit)) {
@@ -1070,8 +1095,8 @@ collect(Context* c, void** p)
         parent = original;
       }
 
-      original = cast<object>(copy, walker.first * BytesPerWord);
+      original = get(copy, walker.first);
-      cast<object>(copy, walker.first * BytesPerWord) = follow(c, original);
+      set(copy, walker.first, follow(c, original));
       goto visit;
     } else {
       // ascend
@@ -1131,16 +1156,16 @@ collect(Context* c, void** p)
 
     if (Debug) {
       fprintf(stderr, "  next is %p (%s) at %p - offset %d from %p (%s)\n",
-              cast<object>(copy, walker.next * BytesPerWord),
+              get(copy, walker.next),
-              segment(c, cast<object>(copy, walker.next * BytesPerWord)),
+              segment(c, get(copy, walker.next)),
-              &cast<object>(copy, walker.next * BytesPerWord),
+              getp(copy, walker.next),
               walker.next,
               copy,
               segment(c, copy));
     }
 
-    original = cast<object>(copy, walker.next * BytesPerWord);
+    original = get(copy, walker.next);
-    cast<object>(copy, walker.next * BytesPerWord) = follow(c, original);
+    set(copy, walker.next, follow(c, original));
     goto visit;
   } else {
     return;
@@ -1236,7 +1261,7 @@ collect(Context* c, Segment* s, unsigned limit)
       Walker(Context* c, object p): c(c), p(p) { }
 
       virtual bool visit(unsigned offset) {
-        collect(c, &cast<object>(p, offset * BytesPerWord));
+        collect(c, getp(p, offset));
         return true;
       }
 

src/main.cpp

@@ -1,8 +1,12 @@
 #include "sys/mman.h"
 #include "sys/types.h"
 #include "sys/stat.h"
+#include <sys/time.h>
+#include <time.h>
 #include "fcntl.h"
 #include "dlfcn.h"
+#include "errno.h"
+#include "pthread.h"
 #include "common.h"
 #include "system.h"
 #include "heap.h"
@@ -86,6 +90,22 @@ dynamicCall(void* function, uint64_t* arguments, uint8_t* argumentTypes,
 
 namespace {
 
+void*
+run(void* t)
+{
+  static_cast<vm::System::Thread*>(t)->run();
+  return 0;
+}
+
+int64_t
+now()
+{
+  timeval tv = { 0, 0 };
+  gettimeofday(&tv, 0);
+  return (static_cast<int64_t>(tv.tv_sec) * 1000) +
+    (static_cast<int64_t>(tv.tv_usec) / 1000);
+}
+
 const char*
 append(vm::System* s, const char* a, const char* b, const char* c,
        const char* d)
@@ -108,17 +128,95 @@ class System: public vm::System {
  public:
   class Monitor: public vm::System::Monitor {
    public:
-    Monitor(vm::System* s): s(s) { }
+    Monitor(vm::System* s): s(s), context(0), depth(0) {
+      pthread_mutex_init(&mutex, 0);
+      pthread_cond_init(&condition, 0);      
+    }
 
-    virtual bool tryAcquire(void*) { return true; }
+    virtual bool tryAcquire(void* context) {
-    virtual void acquire(void*) { }
+      if (this->context == context) {
-    virtual void release(void*) { }
+        ++ depth;
-    virtual void wait(void*) { }
+        return true;
-    virtual void notify(void*) { }
+      } else {
-    virtual void notifyAll(void*) { }
+        switch (pthread_mutex_trylock(&mutex)) {
-    virtual void dispose() { s->free(this);  }
+        case EBUSY:
+          return false;
+
+        case 0:
+          this->context = context;
+          ++ depth;
+          return true;
+
+        default:
+          vm::abort(s);
+        }
+      }
+    }
+
+    virtual void acquire(void* context) {
+      if (this->context != context) {
+        pthread_mutex_lock(&mutex);
+        this->context = context;
+      }
+      ++ depth;
+    }
+
+    virtual void release(void* context) {
+      if (this->context == context) {
+        if (-- depth == 0) {
+          this->context = 0;
+          pthread_mutex_unlock(&mutex);
+        }
+      } else {
+        vm::abort(s);
+      }
+    }
+
+    virtual void wait(void* context, int64_t time) {
+      if (this->context == context) {
+        if (time) {
+          int64_t then = now() + time;
+          timespec ts = { then / 1000, (then % 1000) * 1000 * 1000 };
+          int rv = pthread_cond_timedwait(&condition, &mutex, &ts);
+          assert(s, rv == 0);
+        } else {
+          int rv = pthread_cond_wait(&condition, &mutex);
+          assert(s, rv == 0);
+        }
+      } else {
+        vm::abort(s);
+      }
+    }
+
+    virtual void notify(void* context) {
+      if (this->context == context) {
+        int rv = pthread_cond_signal(&condition);
+        assert(s, rv == 0);
+      } else {
+        vm::abort(s);
+      }
+    }
+
+    virtual void notifyAll(void* context) {
+      if (this->context == context) {
+        int rv = pthread_cond_broadcast(&condition);
+        assert(s, rv == 0);
+      } else {
+        vm::abort(s);
+      }
+    }
+
+    virtual void dispose() {
+      pthread_mutex_destroy(&mutex);
+      pthread_cond_destroy(&condition);
+      s->free(this);
+    }
 
     vm::System* s;
+    pthread_mutex_t mutex;
+    pthread_cond_t condition;
+    void* context;
+    unsigned depth;
   };
 
   class Library: public vm::System::Library {
@@ -149,14 +247,20 @@ class System: public vm::System {
     vm::System::Library* next_;
   };
 
-  System(unsigned limit): limit(limit), count(0) { }
+  System(unsigned limit): limit(limit), count(0) {
+    pthread_mutex_init(&mutex, 0);
+  }
+
+  ~System() {
+    pthread_mutex_destroy(&mutex);
+  }
 
   virtual bool success(Status s) {
     return s == 0;
   }
 
   virtual void* tryAllocate(unsigned size) {
-    // todo: synchronize access
+    pthread_mutex_lock(&mutex);
 
     if (Verbose) {
       fprintf(stderr, "try %d; count: %d; limit: %d\n",
@@ -164,20 +268,26 @@ class System: public vm::System {
     }
 
     if (count + size > limit) {
+      pthread_mutex_unlock(&mutex);
       return 0;
+    } else {
+      uintptr_t* up = static_cast<uintptr_t*>
+        (malloc(size + sizeof(uintptr_t)));
+      if (up == 0) {
+        pthread_mutex_unlock(&mutex);
+        vm::abort(this);
+      } else {
+        *up = size;
+        count += *up;
+      
+        pthread_mutex_unlock(&mutex);
+        return up + 1;
+      }
     }
-
-    uintptr_t* up = static_cast<uintptr_t*>(malloc(size + sizeof(uintptr_t)));
-    if (up == 0) abort();
-
-    *up = size;
-    count += *up;
-
-    return up + 1;
   }
 
   virtual void free(const void* p) {
-    // todo: synchronize access
+    pthread_mutex_lock(&mutex);
 
     if (p) {
       const uintptr_t* up = static_cast<const uintptr_t*>(p) - 1;
@@ -193,10 +303,15 @@ class System: public vm::System {
 
       ::free(const_cast<uintptr_t*>(up));
     }
+
+    pthread_mutex_unlock(&mutex);
   }
 
-  virtual Status start(Thread*) {
+  virtual Status start(Thread* t) {
-    return 1;
+    pthread_t thread;
+    int rv = pthread_create(&thread, 0, run, t);
+    assert(this, rv == 0);
+    return 0;
   }
 
   virtual Status make(vm::System::Monitor** m) {
@@ -232,6 +347,7 @@ class System: public vm::System {
     ::abort();
   }
 
+  pthread_mutex_t mutex;
   unsigned limit;
   unsigned count;
 };

src/system.h

@@ -21,7 +21,7 @@ class System {
     virtual bool tryAcquire(void* id) = 0;
     virtual void acquire(void* id) = 0;
     virtual void release(void* id) = 0;
-    virtual void wait(void* id) = 0;
+    virtual void wait(void* id, int64_t time) = 0;
     virtual void notify(void* id) = 0;
     virtual void notifyAll(void* id) = 0;
     virtual void dispose() = 0;

src/type-generator.cpp

@@ -995,7 +995,7 @@ writeSubtypeAssertions(Output* out, Object* o)
 {
   for (Object* p = typeSubtypes(o); p; p = cdr(p)) {
     Object* st = car(p);
-    out->write(" or objectClass(o) == arrayBodyUnsafe");
+    out->write(" or objectClass(t, o) == arrayBodyUnsafe");
     out->write("(t, t->vm->types, Machine::");
     out->write(capitalize(typeName(st)));
     out->write("Type)");
@@ -1035,8 +1035,8 @@ writeAccessor(Output* out, Object* member, Object* offset, bool unsafe = false)
     if (unsafe) {
       out->write("  assert(t, true);");
     } else {
-      out->write("  assert(t, t->vm->unsafe or objectClass(o) == 0 or ");
+      out->write("  assert(t, t->vm->unsafe or ");
-      out->write("objectClass(o) == arrayBodyUnsafe");
+      out->write("objectClass(t, o) == arrayBodyUnsafe");
       out->write("(t, t->vm->types, Machine::");
       out->write(capitalize(::typeName(memberOwner(member))));
       out->write("Type)");
@@ -1320,7 +1320,8 @@ writeConstructors(Output* out, Object* declarations)
       writeOffset(out, typeOffset(o), true);
       out->write(");\n");
 
-      out->write("  objectClass(o) = arrayBody(t, t->vm->types, Machine::");
+      out->write("  cast<object>(o, 0) ");
+      out->write("= arrayBody(t, t->vm->types, Machine::");
       out->write(capitalize(typeName(o)));
       out->write("Type);\n");
 
@@ -1538,7 +1539,7 @@ writeInitializations(Output* out, Object* declarations)
   out->write("t->vm->types = allocate(t, pad((");
   out->write(count);
   out->write(" * sizeof(void*)) + 4 + sizeof(void*)));\n");
-  out->write("objectClass(t->vm->types) = 0;\n");
+  out->write("cast<object>(t->vm->types, 0) = 0;\n");
   out->write("arrayLength(t, t->vm->types) = ");
   out->write(count);
   out->write(";\n");

src/vm.cpp

@@ -33,12 +33,6 @@ void set(Thread*, object&, object);
 object makeString(Thread*, const char*, ...);
 object makeByteArray(Thread*, const char*, ...);
 
-object&
-objectClass(object o)
-{
-  return cast<object>(o, 0);
-}
-
 enum FieldCode {
   VoidField,
   ByteField,
@@ -163,6 +157,12 @@ class Thread : public JNIEnv {
   object heap[HeapSizeInWords];
 };
 
+inline object
+objectClass(Thread*, object o)
+{
+  return mask(cast<object>(o, 0));
+}
+
 #include "type-declarations.cpp"
 #include "type-constructors.cpp"
 
@@ -489,8 +489,8 @@ collect(Machine* m, Heap::CollectionType type)
     virtual unsigned sizeInWords(void* p) {
       Thread* t = m->rootThread;
 
-      p = m->heap->follow(p);
+      p = m->heap->follow(mask(p));
-      object class_ = m->heap->follow(objectClass(p));
+      object class_ = m->heap->follow(objectClass(t, p));
 
       unsigned n = divide(classFixedSize(t, class_), BytesPerWord);
 
@@ -505,8 +505,8 @@ collect(Machine* m, Heap::CollectionType type)
     virtual void walk(void* p, Heap::Walker* w) {
       Thread* t = m->rootThread;
 
-      p = m->heap->follow(p);
+      p = m->heap->follow(mask(p));
-      object class_ = m->heap->follow(objectClass(p));
+      object class_ = m->heap->follow(objectClass(t, p));
       object objectMask = m->heap->follow(classObjectMask(t, class_));
 
       if (objectMask) {
@@ -599,7 +599,7 @@ enter(Thread* t, Thread::State s)
     t->vm->exclusive = t;
       
     while (t->vm->activeCount > 1) {
-      t->vm->stateLock->wait(t);
+      t->vm->stateLock->wait(t, 0);
     }
   } break;
 
@@ -639,7 +639,7 @@ enter(Thread* t, Thread::State s)
     case Thread::NoState:
     case Thread::IdleState: {
       while (t->vm->exclusive) {
-        t->vm->stateLock->wait(t);
+        t->vm->stateLock->wait(t, 0);
       }
 
       ++ t->vm->activeCount;
@@ -669,7 +669,7 @@ enter(Thread* t, Thread::State s)
     t->state = s;
 
     while (t->vm->liveCount > 1) {
-      t->vm->stateLock->wait(t);
+      t->vm->stateLock->wait(t, 0);
     }
   } break;
 
@@ -762,7 +762,7 @@ make(Thread* t, object class_)
 unsigned
 objectSize(Thread* t, object o)
 {
-  object class_ = objectClass(o);
+  object class_ = objectClass(t, o);
 
   unsigned n = divide(classFixedSize(t, class_), BytesPerWord);
 
@@ -921,8 +921,8 @@ makeUnsatisfiedLinkError(Thread* t, object message)
 inline bool
 isLongOrDouble(Thread* t, object o)
 {
-  return objectClass(o) == arrayBody(t, t->vm->types, Machine::LongType)
+  return objectClass(t, o) == arrayBody(t, t->vm->types, Machine::LongType)
-    or objectClass(o) == arrayBody(t, t->vm->types, Machine::DoubleType);
+    or objectClass(t, o) == arrayBody(t, t->vm->types, Machine::DoubleType);
 }
 
 unsigned
@@ -1139,10 +1139,10 @@ instanceOf(Thread* t, object class_, object o)
     return false;
   }
 
-  if (objectClass(class_)
+  if (objectClass(t, class_)
       == arrayBody(t, t->vm->types, Machine::InterfaceType))
   {
-    for (object oc = objectClass(o); oc; oc = classSuper(t, oc)) {
+    for (object oc = objectClass(t, o); oc; oc = classSuper(t, oc)) {
       object itable = classInterfaceTable(t, oc);
       for (unsigned i = 0; i < arrayLength(t, itable); i += 2) {
         if (arrayBody(t, itable, i) == class_) {
@@ -1151,7 +1151,7 @@ instanceOf(Thread* t, object class_, object o)
       }
     }
   } else {
-    for (object oc = objectClass(o); oc; oc = classSuper(t, oc)) {
+    for (object oc = objectClass(t, o); oc; oc = classSuper(t, oc)) {
       if (oc == class_) {
         return true;
       }
@@ -1165,7 +1165,7 @@ object
 findInterfaceMethod(Thread* t, object method, object o)
 {
   object interface = methodClass(t, method);
-  object itable = classInterfaceTable(t, objectClass(o));
+  object itable = classInterfaceTable(t, objectClass(t, o));
   for (unsigned i = 0; i < arrayLength(t, itable); i += 2) {
     if (arrayBody(t, itable, i) == interface) {
       return arrayBody(t, arrayBody(t, itable, i + 1),
@@ -1185,7 +1185,7 @@ findMethod(Thread* t, object method, object class_)
 inline object
 findVirtualMethod(Thread* t, object method, object o)
 {
-  return findMethod(t, method, objectClass(o));
+  return findMethod(t, method, objectClass(t, o));
 }
 
 bool
@@ -1336,7 +1336,8 @@ parsePool(Thread* t, Stream& s)
 
   for (unsigned i = 0; i < poolCount; ++i) {
     object o = arrayBody(t, pool, i);
-    if (objectClass(o) == arrayBody(t, t->vm->types, Machine::IntArrayType)) {
+    if (objectClass(t, o) == arrayBody(t, t->vm->types, Machine::IntArrayType))
+    {
       switch (intArrayBody(t, o, 0)) {
       case CONSTANT_Class: {
         set(t, arrayBody(t, pool, i),
@@ -1361,7 +1362,8 @@ parsePool(Thread* t, Stream& s)
 
   for (unsigned i = 0; i < poolCount; ++i) {
     object o = arrayBody(t, pool, i);
-    if (objectClass(o) == arrayBody(t, t->vm->types, Machine::IntArrayType)) {
+    if (objectClass(t, o) == arrayBody(t, t->vm->types, Machine::IntArrayType))
+    {
       switch (intArrayBody(t, o, 0)) {
       case CONSTANT_Fieldref:
       case CONSTANT_Methodref:
@@ -2064,7 +2066,8 @@ inline object
 resolveClass(Thread* t, object pool, unsigned index)
 {
   object o = arrayBody(t, pool, index);
-  if (objectClass(o) == arrayBody(t, t->vm->types, Machine::ByteArrayType)) {
+  if (objectClass(t, o) == arrayBody(t, t->vm->types, Machine::ByteArrayType))
+  {
     PROTECT(t, pool);
 
     o = resolveClass(t, o);
@@ -2079,7 +2082,8 @@ inline object
 resolveClass(Thread* t, object container, object& (*class_)(Thread*, object))
 {
   object o = class_(t, container);
-  if (objectClass(o) == arrayBody(t, t->vm->types, Machine::ByteArrayType)) {
+  if (objectClass(t, o) == arrayBody(t, t->vm->types, Machine::ByteArrayType))
+  {
     PROTECT(t, container);
 
     o = resolveClass(t, o);
@@ -2095,7 +2099,8 @@ resolve(Thread* t, object pool, unsigned index,
         object (*find)(Thread*, object, object))
 {
   object o = arrayBody(t, pool, index);
-  if (objectClass(o) == arrayBody(t, t->vm->types, Machine::ReferenceType)) {
+  if (objectClass(t, o) == arrayBody(t, t->vm->types, Machine::ReferenceType))
+  {
     PROTECT(t, pool);
 
     object class_ = resolveClass(t, o, referenceClass);
@@ -2179,7 +2184,7 @@ makeNativeMethodData(Thread* t, object method, void* function, bool builtin)
 inline object
 resolveNativeMethodData(Thread* t, object method)
 {
-  if (objectClass(methodCode(t, method))
+  if (objectClass(t, methodCode(t, method))
       == arrayBody(t, t->vm->types, Machine::ByteArrayType))
   {
     object data = 0;
@@ -2333,7 +2338,7 @@ toString(JNIEnv* e, jobject this_)
 
   object s = makeString
     (t, "%s@%p",
-     &byteArrayBody(t, className(t, objectClass(*this_)), 0),
+     &byteArrayBody(t, className(t, objectClass(t, *this_)), 0),
      *this_);
 
   pushSafe(t, s);
@@ -2493,13 +2498,13 @@ Thread::Thread(Machine* m):
 #include "type-initializations.cpp"
 
     object arrayClass = arrayBody(t, t->vm->types, Machine::ArrayType);
-    set(t, objectClass(t->vm->types), arrayClass);
+    set(t, cast<object>(t->vm->types, 0), arrayClass);
 
     object classClass = arrayBody(t, m->types, Machine::ClassType);
-    set(t, objectClass(classClass), classClass);
+    set(t, cast<object>(classClass, 0), classClass);
 
     object intArrayClass = arrayBody(t, m->types, Machine::IntArrayType);
-    set(t, objectClass(intArrayClass), classClass);
+    set(t, cast<object>(intArrayClass, 0), classClass);
 
     m->unsafe = false;
 
@@ -2668,7 +2673,7 @@ run(Thread* t)
   case arraylength: {
     object array = pop(t);
     if (LIKELY(array)) {
-      if (objectClass(array)
+      if (objectClass(t, array)
           == arrayBody(t, t->vm->types, Machine::ObjectArrayType))
       {
         push(t, makeInt(t, objectArrayLength(t, array)));
@@ -2832,7 +2837,7 @@ run(Thread* t)
       if (not instanceOf(t, class_, stack[sp - 1])) {
         object message = makeString
           (t, "%s as %s",
-           &byteArrayBody(t, className(t, objectClass(stack[sp - 1])), 0),
+           &byteArrayBody(t, className(t, objectClass(t, stack[sp - 1])), 0),
            &byteArrayBody(t, className(t, class_), 0));
         exception = makeClassCastException(t, message);
         goto throw_;
@@ -3639,6 +3644,26 @@ run(Thread* t)
     push(t, makeLong(t, longValue(t, a) ^ longValue(t, b)));
   } goto loop;
 
+//   case monitorenter: {
+//     object o = pop(t);
+//     if (LIKELY(o)) {
+//       objectMonitor(t, o)->acquire(t);
+//     } else {
+//       exception = makeNullPointerException(t);
+//       goto throw_;
+//     }
+//   } goto loop;
+
+//   case monitorexit: {
+//     object o = pop(t);
+//     if (LIKELY(o)) {
+//       objectMonitor(t, o)->release(t);
+//     } else {
+//       exception = makeNullPointerException(t);
+//       goto throw_;
+//     }
+//   } goto loop;
+
   case new_: {
     uint8_t index1 = codeBody(t, code, ip++);
     uint8_t index2 = codeBody(t, code, ip++);
@@ -3948,7 +3973,7 @@ run(Thread* t)
           arrayBody(t, codePool(t, code), exceptionHandlerCatchType(eh) - 1);
 
         if (catchType == 0 or
-            (objectClass(catchType)
+            (objectClass(t, catchType)
              == arrayBody(t, t->vm->types, Machine::ClassType) and
              instanceOf(t, catchType, exception)))
         {
@@ -3970,7 +3995,7 @@ run(Thread* t)
     }
 
     fprintf(stderr, "%s", &byteArrayBody
-            (t, className(t, objectClass(exception)), 0));
+            (t, className(t, objectClass(t, exception)), 0));
   
     if (throwableMessage(t, exception)) {
       object m = throwableMessage(t, exception);
@@ -3994,17 +4019,17 @@ run(Thread* t)
       int line = lineNumber
         (t, stackTraceElementMethod(t, e), stackTraceElementIp(t, e));
 
-      fprintf(stderr, "  at %s.%s", class_, method);
+      fprintf(stderr, "  at %s.%s ", class_, method);
 
       switch (line) {
       case NativeLine:
         fprintf(stderr, "(native)\n");
         break;
       case UnknownLine:
-        fprintf(stderr, "(unknown)\n");
+        fprintf(stderr, "(unknown line)\n");
         break;
       default:
-        fprintf(stderr, "(%d)\n", line);
+        fprintf(stderr, "(line %d)\n", line);
       }
     }
   }