diff --git a/common/JackActivationCount.h b/common/JackActivationCount.h
index 7efc031c9..a77e6e6db 100644
--- a/common/JackActivationCount.h
+++ b/common/JackActivationCount.h
@@ -33,7 +33,7 @@ struct JackClientControl;
 \brief Client activation counter.
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 class JackActivationCount
 {
 
@@ -74,7 +74,7 @@ class JackActivationCount
             return fValue;
         }
 
-}  POST_PACKED_STRUCTURE;
+};
 
 } // end of namespace
 
diff --git a/common/JackAtomicArrayState.h b/common/JackAtomicArrayState.h
index a2c0139d6..16d2f19c6 100644
--- a/common/JackAtomicArrayState.h
+++ b/common/JackAtomicArrayState.h
@@ -30,7 +30,7 @@ namespace Jack
 /*!
 \brief Counter for CAS
 */
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 struct AtomicArrayCounter
 {
     union {
@@ -68,7 +68,7 @@ struct AtomicArrayCounter
         return *this;
     }
     
-} POST_PACKED_STRUCTURE;
+};
 
 #define Counter1(e) (e).info.fLongVal
 #define GetIndex1(e, state) ((e).info.scounter.fByteVal[state])
@@ -109,7 +109,7 @@ struct AtomicArrayCounter
 
 // CHECK livelock
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 template <class T>
 class JackAtomicArrayState
 {
@@ -249,7 +249,7 @@ class JackAtomicArrayState
             WriteNextStateStopAux(state);
         }
 
-} POST_PACKED_STRUCTURE;
+};
 
 } // end of namespace
 
diff --git a/common/JackAtomicState.h b/common/JackAtomicState.h
index 1eef4e11b..ea166c156 100644
--- a/common/JackAtomicState.h
+++ b/common/JackAtomicState.h
@@ -31,7 +31,7 @@ namespace Jack
 \brief Counter for CAS
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 struct AtomicCounter
 {
     union {
@@ -70,7 +70,7 @@ struct AtomicCounter
         return *this;
     }
 
-} POST_PACKED_STRUCTURE;
+};
 
 #define Counter(e) (e).info.fLongVal
 #define CurIndex(e) (e).info.scounter.fShortVal1
@@ -85,7 +85,7 @@ struct AtomicCounter
 
 // CHECK livelock
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 template <class T>
 class JackAtomicState
 {
@@ -254,7 +254,7 @@ class JackAtomicState
         }
         */
         
-} POST_PACKED_STRUCTURE;
+};
 
 } // end of namespace
 
diff --git a/common/JackClientControl.h b/common/JackClientControl.h
index 23b536afa..7c4b51505 100644
--- a/common/JackClientControl.h
+++ b/common/JackClientControl.h
@@ -34,7 +34,7 @@ namespace Jack
 \brief Client control possibly in shared memory.
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 struct JackClientControl : public JackShmMemAble
 {
     char fName[JACK_CLIENT_NAME_SIZE + 1];
@@ -89,7 +89,7 @@ struct JackClientControl : public JackShmMemAble
         fSessionID = uuid;
     }
 
-} POST_PACKED_STRUCTURE;
+};
 
 } // end of namespace
 
diff --git a/common/JackConnectionManager.h b/common/JackConnectionManager.h
index 5041557a1..23bd0f88a 100644
--- a/common/JackConnectionManager.h
+++ b/common/JackConnectionManager.h
@@ -36,7 +36,7 @@ struct JackClientControl;
 \brief Utility class.
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 template <int SIZE>
 class JackFixedArray
 {
@@ -117,13 +117,13 @@ class JackFixedArray
             return fCounter;
         }
 
-} POST_PACKED_STRUCTURE;
+};
 
 /*!
 \brief Utility class.
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 template <int SIZE>
 class JackFixedArray1 : public JackFixedArray<SIZE>
 {
@@ -154,13 +154,13 @@ class JackFixedArray1 : public JackFixedArray<SIZE>
             }
         }
 
-} POST_PACKED_STRUCTURE;
+};
 
 /*!
 \brief Utility class.
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 template <int SIZE>
 class JackFixedMatrix
 {
@@ -250,13 +250,13 @@ class JackFixedMatrix
         }
 
 
-} POST_PACKED_STRUCTURE;
+};
 
 /*!
 \brief Utility class.
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 template <int SIZE>
 class JackLoopFeedback
 {
@@ -364,13 +364,13 @@ class JackLoopFeedback
             return -1;
         }
 
-} POST_PACKED_STRUCTURE;
+};
 
 /*!
 \brief For client timing measurements.
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 struct JackClientTiming
 {
     jack_time_t fSignaledAt;
@@ -393,7 +393,7 @@ struct JackClientTiming
         fStatus = NotTriggered;
     }
 
-} POST_PACKED_STRUCTURE;
+};
 
 /*!
 \brief Connection manager.
@@ -407,7 +407,7 @@ struct JackClientTiming
 </UL>
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 class SERVER_EXPORT JackConnectionManager
 {
 
@@ -487,7 +487,7 @@ class SERVER_EXPORT JackConnectionManager
         int SuspendRefNum(JackClientControl* control, JackSynchro* table, JackClientTiming* timing, long time_out_usec);
         void TopologicalSort(std::vector<jack_int_t>& sorted);
 
-} POST_PACKED_STRUCTURE;
+};
 
 } // end of namespace
 
diff --git a/common/JackEngineControl.h b/common/JackEngineControl.h
index 2a254b8f1..efb359ca8 100644
--- a/common/JackEngineControl.h
+++ b/common/JackEngineControl.h
@@ -41,11 +41,13 @@ class JackGraphManager;
 #define JACK_ENGINE_ROLLING_COUNT 32
 #define JACK_ENGINE_ROLLING_INTERVAL 1024
 
+typedef JACK_ALIGNED_TYPE(UInt64) jack_UInt64;
+
 /*!
 \brief Engine control in shared memory.
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 struct SERVER_EXPORT JackEngineControl : public JackShmMem
 {
     // Shared state
@@ -81,9 +83,9 @@ struct SERVER_EXPORT JackEngineControl : public JackShmMem
     float fCPULoad;
 
     // For OSX thread
-    UInt64 fPeriod;
-    UInt64 fComputation;
-    UInt64 fConstraint;
+    jack_UInt64 fPeriod;
+    jack_UInt64 fComputation;
+    jack_UInt64 fConstraint;
 
     // Timer
     JackFrameTimer fFrameTimer;
@@ -182,7 +184,7 @@ struct SERVER_EXPORT JackEngineControl : public JackShmMem
     void CalcCPULoad(JackClientInterface** table, JackGraphManager* manager, jack_time_t cur_cycle_begin, jack_time_t prev_cycle_end);
     void ResetRollingUsecs();
 
-} POST_PACKED_STRUCTURE;
+};
 
 } // end of namespace
 
diff --git a/common/JackEngineProfiling.h b/common/JackEngineProfiling.h
index 04fdb953d..88be1cd54 100644
--- a/common/JackEngineProfiling.h
+++ b/common/JackEngineProfiling.h
@@ -37,7 +37,7 @@ namespace Jack
 \brief Timing stucture for a client.
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 struct JackTimingMeasureClient
 {
     int fRefNum;
@@ -54,13 +54,13 @@ struct JackTimingMeasureClient
         fStatus((jack_client_state_t)0)
     {}
     
-} POST_PACKED_STRUCTURE;
+};
 
 /*!
 \brief Timing interval in the global table for a given client
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 struct JackTimingClientInterval
 {
     int fRefNum;
@@ -74,13 +74,13 @@ struct JackTimingClientInterval
          fEndInterval(-1)
     {}
     
-} POST_PACKED_STRUCTURE;
+};
 
 /*!
 \brief Timing stucture for a table of clients.
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 struct JackTimingMeasure
 {
     unsigned int fAudioCycle;
@@ -96,7 +96,7 @@ struct JackTimingMeasure
         fPrevCycleEnd(0)
     {}
     
-} POST_PACKED_STRUCTURE;
+};
 
 /*!
 \brief Client timing monitoring.
@@ -105,7 +105,7 @@ struct JackTimingMeasure
 class JackClientInterface;
 class JackGraphManager;
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 class SERVER_EXPORT JackEngineProfiling
 {
 
@@ -132,7 +132,7 @@ class SERVER_EXPORT JackEngineProfiling
                     
         JackTimingMeasure* GetCurMeasure();
 
-} POST_PACKED_STRUCTURE;
+};
 
 } // end of namespace
 
diff --git a/common/JackFilters.h b/common/JackFilters.h
index e245d58bf..cf990b67e 100644
--- a/common/JackFilters.h
+++ b/common/JackFilters.h
@@ -38,7 +38,7 @@ namespace Jack
 
     #define MAX_SIZE 64
 
-    PRE_PACKED_STRUCTURE
+    /* Note: This class must be kept 32/64 clean! */
     struct JackFilter
     {
 
@@ -66,9 +66,9 @@ namespace Jack
             return mean / MAX_SIZE;
         }
 
-    } POST_PACKED_STRUCTURE;
+    };
 
-    PRE_PACKED_STRUCTURE
+    /* Note: This class must be kept 32/64 clean! */
     class JackDelayLockedLoop
     {
 
@@ -149,9 +149,9 @@ namespace Jack
                 return fCurrentWakeup;
             }
 
-    } POST_PACKED_STRUCTURE;
+    };
 
-    PRE_PACKED_STRUCTURE
+    /* Note: This class must be kept 32/64 clean! */
     class JackAtomicDelayLockedLoop : public JackAtomicState<JackDelayLockedLoop>
     {
          public:
@@ -215,7 +215,7 @@ namespace Jack
 
                 return res;
             }
-    } POST_PACKED_STRUCTURE;
+    };
 
 #endif
 
diff --git a/common/JackFrameTimer.h b/common/JackFrameTimer.h
index a32e7423f..13916e1f3 100644
--- a/common/JackFrameTimer.h
+++ b/common/JackFrameTimer.h
@@ -32,7 +32,7 @@ namespace Jack
 \brief A structure used for time management.
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 class SERVER_EXPORT JackTimer
 {
 
@@ -69,13 +69,13 @@ class SERVER_EXPORT JackTimer
             return fCurrentWakeup;
         }
 
-} POST_PACKED_STRUCTURE;
+};
 
 /*!
 \brief A class using the JackAtomicState to manage jack time.
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 class SERVER_EXPORT JackFrameTimer : public JackAtomicState<JackTimer>
 {
 
@@ -97,7 +97,7 @@ class SERVER_EXPORT JackFrameTimer : public JackAtomicState<JackTimer>
         void IncFrameTime(jack_nframes_t buffer_size, jack_time_t callback_usecs, jack_time_t period_usecs);
         void ReadFrameTime(JackTimer* timer);
 
-} POST_PACKED_STRUCTURE;
+};
 
 
 } // end of namespace
diff --git a/common/JackGraphManager.h b/common/JackGraphManager.h
index 15f0275f2..9c6d8aad0 100644
--- a/common/JackGraphManager.h
+++ b/common/JackGraphManager.h
@@ -36,7 +36,7 @@ namespace Jack
 \brief Graph manager: contains the connection manager and the port array.
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 class SERVER_EXPORT JackGraphManager : public JackShmMem, public JackAtomicState<JackConnectionManager>
 {
 
@@ -137,7 +137,7 @@ class SERVER_EXPORT JackGraphManager : public JackShmMem, public JackAtomicState
         static JackGraphManager* Allocate(int port_max);
         static void Destroy(JackGraphManager* manager);
 
-} POST_PACKED_STRUCTURE;
+};
 
 
 } // end of namespace
diff --git a/common/JackNetTool.h b/common/JackNetTool.h
index 5d4559a1b..dad7d4439 100644
--- a/common/JackNetTool.h
+++ b/common/JackNetTool.h
@@ -84,7 +84,7 @@ namespace Jack
     are kept in LITTLE_ENDIAN format (to avoid 2 conversions in the more common LITTLE_ENDIAN <==> LITTLE_ENDIAN connection case).
     */
 
-    PRE_PACKED_STRUCTURE
+    /* Note: This class must be kept 32/64 clean! */
     struct _session_params
     {
         char fPacketType[8];                //packet type ('param')
@@ -106,7 +106,7 @@ namespace Jack
         uint32_t fKBps;                     //KB per second for CELT encoder
         uint32_t fSlaveSyncMode;            //is the slave in sync mode ?
         uint32_t fNetworkLatency;           //network latency
-    } POST_PACKED_STRUCTURE;
+    };
 
 //net status **********************************************************************************
 
@@ -167,7 +167,7 @@ namespace Jack
 
     */
 
-    PRE_PACKED_STRUCTURE
+    /* Note: This class must be kept 32/64 clean! */
     struct _packet_header
     {
         char fPacketType[8];        //packet type ('headr')
@@ -180,7 +180,7 @@ namespace Jack
         uint32_t fCycle;            //process cycle counter
         uint32_t fSubCycle;         //midi/audio subcycle counter
         uint32_t fIsLastPckt;       //is it the last packet of a given cycle ('y' or 'n')
-    } POST_PACKED_STRUCTURE;
+    };
 
 //net timebase master
 
@@ -205,14 +205,14 @@ namespace Jack
     \Brief This structure contains transport data to be sent over the network
     */
 
-    PRE_PACKED_STRUCTURE
+    /* Note: This class must be kept 32/64 clean! */
     struct _net_transport_data
     {
         uint32_t fNewState;             //is it a state change
         uint32_t fTimebaseMaster;       //is there a new timebase master
         int32_t fState;                 //current cycle state
         jack_position_t fPosition;      //current cycle position
-    } POST_PACKED_STRUCTURE;
+    };
 
  //midi data ***********************************************************************************
 
diff --git a/common/JackPort.h b/common/JackPort.h
index f7a601ed3..4198d83c3 100644
--- a/common/JackPort.h
+++ b/common/JackPort.h
@@ -35,7 +35,7 @@ namespace Jack
 \brief Base class for port.
 */
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 class SERVER_EXPORT JackPort
 {
 
@@ -113,7 +113,7 @@ class SERVER_EXPORT JackPort
 
         int GetRefNum() const;
 
-} POST_PACKED_STRUCTURE;
+};
 
 } // end of namespace
 
diff --git a/common/JackTransportEngine.h b/common/JackTransportEngine.h
index b6a4ddcf8..348467834 100644
--- a/common/JackTransportEngine.h
+++ b/common/JackTransportEngine.h
@@ -89,7 +89,7 @@ We have:
 
 class JackClientInterface;
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 class SERVER_EXPORT JackTransportEngine : public JackAtomicArrayState<jack_position_t>
 {
 
@@ -194,7 +194,7 @@ class SERVER_EXPORT JackTransportEngine : public JackAtomicArrayState<jack_posit
             fNetworkSync = sync;
         }
 
-} POST_PACKED_STRUCTURE;
+};
 
 } // end of namespace
 
diff --git a/common/jack/systemdeps.h b/common/jack/systemdeps.h
index b4a14720c..1bf24e6a0 100644
--- a/common/jack/systemdeps.h
+++ b/common/jack/systemdeps.h
@@ -20,38 +20,29 @@ Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 #ifndef __jack_systemdeps_h__
 #define __jack_systemdeps_h__
 
-#ifndef POST_PACKED_STRUCTURE
+#ifndef JACK_ALIGNED_TYPE
 
     #ifdef __GNUC__
-        /* POST_PACKED_STRUCTURE needs to be a macro which
-           expands into a compiler directive. The directive must
-           tell the compiler to arrange the preceding structure
-           declaration so that it is packed on byte-boundaries rather 
-           than use the natural alignment of the processor and/or
-           compiler.
-        */
 
-        #define PRE_PACKED_STRUCTURE
-        #define POST_PACKED_STRUCTURE __attribute__((__packed__))
+
+        #define JACK_ALIGN(N) __attribute__((__aligned__(N)))
+
+        /* A utility for declaring a type which is aligned to its size. */
+        #define JACK_ALIGNED_TYPE(T) JACK_ALIGN(sizeof(T)) T
 
     #else
     
         #ifdef _MSC_VER
-            #define PRE_PACKED_STRUCTURE1 __pragma(pack(push,1))
-            #define PRE_PACKED_STRUCTURE    PRE_PACKED_STRUCTURE1
-            /* PRE_PACKED_STRUCTURE needs to be a macro which
-            expands into a compiler directive. The directive must
-            tell the compiler to arrange the following structure
-            declaration so that it is packed on byte-boundaries rather
-            than use the natural alignment of the processor and/or
-            compiler.
-            */
-            #define POST_PACKED_STRUCTURE ;__pragma(pack(pop))
-            /* and POST_PACKED_STRUCTURE needs to be a macro which
-            restores the packing to its previous setting */
+
+            #define JACK_ALIGN(N) __declspec(align(N))
+
+            /* A utility for declaring a type which is aligned to its size. */
+            #define JACK_ALIGNED_TYPE(T) JACK_ALIGN(sizeof(T)) T
+
         #else
-            #define PRE_PACKED_STRUCTURE
-            #define POST_PACKED_STRUCTURE
+
+            #define JACK_ALIGN(N)
+            #define JACK_ALIGNED_TYPE(T) T
         #endif /* _MSC_VER */
 
     #endif /* __GNUC__ */
diff --git a/common/jack/types.h b/common/jack/types.h
index fa059159f..eac6aa966 100644
--- a/common/jack/types.h
+++ b/common/jack/types.h
@@ -23,6 +23,14 @@
 
 #include <jack/systemdeps.h>
 
+/* To facilitate direct sharing between 32-bit and 64-bit code, declare
+ * fully-aligned typedefs for types which would otherwise have differing
+ * alignment between the two.
+ */
+typedef JACK_ALIGNED_TYPE(double)   jack_double;
+typedef JACK_ALIGNED_TYPE(int64_t)  jack_int64_t;
+typedef JACK_ALIGNED_TYPE(uint64_t) jack_uint64_t;
+
 typedef int32_t jack_shmsize_t;
 
 /**
@@ -39,7 +47,7 @@ typedef uint32_t        jack_nframes_t;
  * Type used to represent the value of free running
  * monotonic clock with units of microseconds.
  */
-typedef uint64_t jack_time_t;
+typedef jack_uint64_t jack_time_t;
 
 /**
  *  Maximum size of @a load_init string passed to an internal client
@@ -259,7 +267,7 @@ typedef void (*JackLatencyCallback)(jack_latency_callback_mode_t mode, void *arg
 /**
  * the new latency API operates on Ranges.
  */
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 struct _jack_latency_range
 {
     /**
@@ -270,7 +278,7 @@ struct _jack_latency_range
      * maximum latency
      */
     jack_nframes_t max;
-} POST_PACKED_STRUCTURE;
+};
 
 typedef struct _jack_latency_range jack_latency_range_t;
 
@@ -530,7 +538,7 @@ typedef enum {
 
 } jack_transport_state_t;
 
-typedef uint64_t jack_unique_t;         /**< Unique ID (opaque) */
+typedef jack_uint64_t jack_unique_t;    /**< Unique ID (opaque) */
 
 /**
  * Optional struct jack_position_t fields.
@@ -549,7 +557,7 @@ typedef enum {
 #define JACK_POSITION_MASK (JackPositionBBT|JackPositionTimecode)
 #define EXTENDED_TIME_INFO
 
-PRE_PACKED_STRUCTURE
+/* Note: This class must be kept 32/64 clean! */
 struct _jack_position {
 
     /* these four cannot be set from clients: the server sets them */
@@ -564,16 +572,16 @@ struct _jack_position {
     int32_t             bar;            /**< current bar */
     int32_t             beat;           /**< current beat-within-bar */
     int32_t             tick;           /**< current tick-within-beat */
-    double              bar_start_tick;
+    jack_double         bar_start_tick;
 
     float               beats_per_bar;  /**< time signature "numerator" */
     float               beat_type;      /**< time signature "denominator" */
-    double              ticks_per_beat;
-    double              beats_per_minute;
+    jack_double         ticks_per_beat;
+    jack_double         beats_per_minute;
 
     /* JackPositionTimecode fields:     (EXPERIMENTAL: could change) */
-    double              frame_time;     /**< current time in seconds */
-    double              next_time;      /**< next sequential frame_time
+    jack_double         frame_time;     /**< current time in seconds */
+    jack_double         next_time;      /**< next sequential frame_time
                          (unless repositioned) */
 
     /* JackBBTFrameOffset fields: */
@@ -616,7 +624,7 @@ struct _jack_position {
     /* When (unique_1 == unique_2) the contents are consistent. */
     jack_unique_t       unique_2;       /**< unique ID */
 
-} POST_PACKED_STRUCTURE;
+};
 
 typedef struct _jack_position jack_position_t;
 
diff --git a/common/shm.h b/common/shm.h
index c539aa9fb..562de20e1 100644
--- a/common/shm.h
+++ b/common/shm.h
@@ -149,15 +149,15 @@ extern "C"
      * attached to the address space.
      */
 
-    PRE_PACKED_STRUCTURE
+    /* Note: This class must be kept 32/64 clean! */
     struct _jack_shm_info {
         jack_shm_registry_index_t index;       /* offset into the registry */
         uint32_t size;
-        union {
+        JACK_ALIGN(8) union {
             void *attached_at;  /* address where attached */
             char ptr_size[8];
         } ptr;  /* a "pointer" that has the same 8 bytes size when compling in 32 or 64 bits */
-    } POST_PACKED_STRUCTURE;
+    };
     
     typedef struct _jack_shm_info jack_shm_info_t;