Fix alignment of fields for atomic accesses (#761)

* Assert alignment is suitable for atomic accesses

* Move fields and pad to meet alignment constraints

* Add padding to JackEngineControl to account for inherited data

* Parenthesise padding length for clarity

* Revert "Parenthesise padding length for clarity"

This reverts commit 1f757b9ece5e3b032743c6c5ac49e83c3928e3de.

* Revert "Add padding to JackEngineControl to account for inherited data"

This reverts commit 3d8c7d83ad9483280f623171af7e40ccc76cef38.

* Revert "Move fields and pad to meet alignment constraints"

This reverts commit ff631bbbdc2279df05f3a18dd44e8fd68be2e04d.

* Assure alignment by using 'alignas' on fields

11 files changed, 36 insertions, 11 deletions

diff --git a/common/JackActivationCount.h b/common/JackActivationCount.h
index 7efc031c..f9ef8366 100644
--- a/common/JackActivationCount.h
+++ b/common/JackActivationCount.h
@@ -39,13 +39,16 @@ class JackActivationCount
 
     private:
 
-        SInt32 fValue;
+        alignas(SInt32) SInt32 fValue;
         SInt32 fCount;
 
     public:
 
         JackActivationCount(): fValue(0), fCount(0)
-        {}
+        {
+            static_assert(offsetof(JackActivationCount, fValue) % sizeof(fValue) == 0,
+                          "fValue must be aligned within JackActivationCount");
+        }
 
         bool Signal(JackSynchro* synchro, JackClientControl* control);
 
diff --git a/common/JackAtomicArrayState.h b/common/JackAtomicArrayState.h
index 51ec65d9..b664e815 100644
--- a/common/JackAtomicArrayState.h
+++ b/common/JackAtomicArrayState.h
@@ -23,6 +23,7 @@
 #include "JackAtomic.h"
 #include "JackCompilerDeps.h"
 #include <string.h> // for memcpy
+#include <cstddef>
 
 namespace Jack
 {
@@ -121,7 +122,7 @@ class JackAtomicArrayState
         // fState[2] ==> request
 
         T fState[3];
-        volatile AtomicArrayCounter fCounter;
+        alignas(UInt32) volatile AtomicArrayCounter fCounter;
 
         UInt32 WriteNextStateStartAux(int state, bool* result)
         {
@@ -159,6 +160,8 @@ class JackAtomicArrayState
 
         JackAtomicArrayState()
         {
+            static_assert(offsetof(JackAtomicArrayState, fCounter) % sizeof(fCounter) == 0,
+                          "fCounter must be aligned within JackAtomicArrayState");
             Counter1(fCounter) = 0;
         }
 
diff --git a/common/JackAtomicState.h b/common/JackAtomicState.h
index 6f90d66a..26d6a565 100644
--- a/common/JackAtomicState.h
+++ b/common/JackAtomicState.h
@@ -23,6 +23,7 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 #include "JackAtomic.h"
 #include "JackCompilerDeps.h"
 #include <string.h> // for memcpy
+#include <cstddef>
 
 namespace Jack
 {
@@ -93,7 +94,7 @@ class JackAtomicState
     protected:
 
         T fState[2];
-        volatile AtomicCounter fCounter;
+        alignas(UInt32) volatile AtomicCounter fCounter;
         SInt32 fCallWriteCounter;
 
         UInt32 WriteNextStateStartAux()
@@ -131,6 +132,8 @@ class JackAtomicState
 
         JackAtomicState()
         {
+            static_assert(offsetof(JackAtomicState, fCounter) % sizeof(fCounter) == 0,
+                          "fCounter must be aligned within JackAtomicState");
             Counter(fCounter) = 0;
             fCallWriteCounter = 0;
         }
diff --git a/common/JackConnectionManager.cpp b/common/JackConnectionManager.cpp
index a0cc0439..db240d22 100644
--- a/common/JackConnectionManager.cpp
+++ b/common/JackConnectionManager.cpp
@@ -32,6 +32,9 @@ namespace Jack
 JackConnectionManager::JackConnectionManager()
 {
     int i;
+    static_assert(offsetof(JackConnectionManager, fInputCounter) % sizeof(UInt32) == 0,
+                  "fInputCounter must be aligned within JackConnectionManager");
+
     jack_log("JackConnectionManager::InitConnections size = %ld ", sizeof(JackConnectionManager));
 
     for (i = 0; i < PORT_NUM_MAX; i++) {
diff --git a/common/JackConnectionManager.h b/common/JackConnectionManager.h
index ead32092..bd071685 100644
--- a/common/JackConnectionManager.h
+++ b/common/JackConnectionManager.h
@@ -417,7 +417,7 @@ class SERVER_EXPORT JackConnectionManager
         JackFixedArray1<PORT_NUM_FOR_CLIENT> fInputPort[CLIENT_NUM];	/*! Table of input port per refnum : to find a refnum for a given port */
         JackFixedArray<PORT_NUM_FOR_CLIENT> fOutputPort[CLIENT_NUM];	/*! Table of output port per refnum : to find a refnum for a given port */
         JackFixedMatrix<CLIENT_NUM> fConnectionRef;						/*! Table of port connections by (refnum , refnum) */
-        JackActivationCount fInputCounter[CLIENT_NUM];					/*! Activation counter per refnum */
+        alignas(UInt32) JackActivationCount fInputCounter[CLIENT_NUM];	/*! Activation counter per refnum */
         JackLoopFeedback<CONNECTION_NUM_FOR_PORT> fLoopFeedback;		/*! Loop feedback connections */
 
         bool IsLoopPathAux(int ref1, int ref2) const;
diff --git a/common/JackEngineControl.h b/common/JackEngineControl.h
index 8626a161..a2bb7b11 100644
--- a/common/JackEngineControl.h
+++ b/common/JackEngineControl.h
@@ -64,7 +64,7 @@ struct SERVER_EXPORT JackEngineControl : public JackShmMem
     int fClientPriority;
     int fMaxClientPriority;
     char fServerName[JACK_SERVER_NAME_SIZE+1];
-    JackTransportEngine fTransport;
+    alignas(UInt32) JackTransportEngine fTransport;
     jack_timer_type_t fClockSource;
     int fDriverNum;
     bool fVerbose;
@@ -86,14 +86,18 @@ struct SERVER_EXPORT JackEngineControl : public JackShmMem
     UInt64 fConstraint;
 
     // Timer
-    JackFrameTimer fFrameTimer;
+    alignas(UInt32) JackFrameTimer fFrameTimer;
 
 #ifdef JACK_MONITOR
     JackEngineProfiling fProfiler;
 #endif
 
     JackEngineControl(bool sync, bool temporary, long timeout, bool rt, long priority, bool verbose, jack_timer_type_t clock, const char* server_name)
-    {
+      {
+        static_assert(offsetof(JackEngineControl, fTransport) % sizeof(UInt32) == 0,
+                      "fTransport must be aligned within JackEngineControl");
+        static_assert(offsetof(JackEngineControl, fFrameTimer) % sizeof(UInt32) == 0,
+                      "fFrameTimer must be aligned within JackEngineControl");
         fBufferSize = 512;
         fSampleRate = 48000;
         fPeriodUsecs = jack_time_t(1000000.f / fSampleRate * fBufferSize);
diff --git a/common/JackMessageBuffer.cpp b/common/JackMessageBuffer.cpp
index cd197993..f821cf4f 100644
--- a/common/JackMessageBuffer.cpp
+++ b/common/JackMessageBuffer.cpp
@@ -38,7 +38,10 @@ JackMessageBuffer::JackMessageBuffer()
     fOutBuffer(0),
     fOverruns(0),
     fRunning(false)
-{}
+{
+    static_assert(offsetof(JackMessageBuffer, fOverruns) % sizeof(fOverruns) == 0,
+                  "fOverruns must be aligned within JackMessageBuffer");
+}
 
 JackMessageBuffer::~JackMessageBuffer()
 {}
diff --git a/common/JackMessageBuffer.h b/common/JackMessageBuffer.h
index fc0d7177..3c796bde 100644
--- a/common/JackMessageBuffer.h
+++ b/common/JackMessageBuffer.h
@@ -64,7 +64,7 @@ class JackMessageBuffer : public JackRunnableInterface
         JackProcessSync fGuard;
         volatile unsigned int fInBuffer;
         volatile unsigned int fOutBuffer;
-        SInt32 fOverruns;
+        alignas(SInt32) SInt32 fOverruns;
         bool fRunning;
 
         void Flush();
diff --git a/common/JackTransportEngine.cpp b/common/JackTransportEngine.cpp
index 5c0fa8d0..09bf44d7 100644
--- a/common/JackTransportEngine.cpp
+++ b/common/JackTransportEngine.cpp
@@ -36,6 +36,8 @@ namespace Jack
 
 JackTransportEngine::JackTransportEngine(): JackAtomicArrayState<jack_position_t>()
 {
+    static_assert(offsetof(JackTransportEngine, fWriteCounter) % sizeof(fWriteCounter) == 0,
+                  "fWriteCounter must be first member of JackTransportEngine to ensure its alignment");
     fTransportState = JackTransportStopped;
     fTransportCmd = fPreviousCmd = TransportCommandStop;
     fSyncTimeout = 10000000;	/* 10 seconds default...
diff --git a/common/JackTransportEngine.h b/common/JackTransportEngine.h
index e00a3138..afdfcf17 100644
--- a/common/JackTransportEngine.h
+++ b/common/JackTransportEngine.h
@@ -104,7 +104,7 @@ class SERVER_EXPORT JackTransportEngine : public JackAtomicArrayState<jack_posit
         bool fPendingPos;
         bool fNetworkSync;
         bool fConditionnal;
-        SInt32 fWriteCounter;
+        alignas(SInt32) SInt32 fWriteCounter;
 
         bool CheckAllRolling(JackClientInterface** table);
         void MakeAllStartingLocating(JackClientInterface** table);
diff --git a/macosx/JackAtomic_os.h b/macosx/JackAtomic_os.h
index de635dee..5b2715a4 100644
--- a/macosx/JackAtomic_os.h
+++ b/macosx/JackAtomic_os.h
@@ -21,6 +21,7 @@ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 #define __JackAtomic_APPLE__
 
 #include "JackTypes.h"
+#include <cassert>
 
 #if defined(__ppc__) || defined(__ppc64__)
 
@@ -67,8 +68,11 @@ static inline char CAS(volatile UInt32 value, UInt32 newvalue, volatile void* ad
 
 #else
 
+#include <stdio.h>
 static inline char CAS(volatile UInt32 value, UInt32 newvalue, volatile void* addr)
 {
+    // Assert pointer is 32-bit aligned
+    assert(((long)addr & (sizeof(int)-1)) == 0);
     return __sync_bool_compare_and_swap ((UInt32*)addr, value, newvalue);
 }