From 199d1667ff1d0558f631fb21774bda9f8eace368 Mon Sep 17 00:00:00 2001
From: Kevin Bracey <kevin.bracey@arm.com>
Date: Mon, 10 Sep 2018 11:00:08 +0300
Subject: [PATCH 1/2] Make SingletonPtr methods const

Make get() and operators * and -> of SingletonPtr const - they are
logically const and thread-safe, despite the construction on first call.
This construction is "invisible" to the caller of those methods.
---
 platform/SingletonPtr.h | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/platform/SingletonPtr.h b/platform/SingletonPtr.h
index fd3112e590..57fc76b154 100644
--- a/platform/SingletonPtr.h
+++ b/platform/SingletonPtr.h
@@ -88,7 +88,7 @@ struct SingletonPtr {
      * @returns
      *   A pointer to the singleton
      */
-    T *get()
+    T *get() const
     {
         if (NULL == _ptr) {
             singleton_lock();
@@ -108,7 +108,7 @@ struct SingletonPtr {
      * @returns
      *   A pointer to the singleton
      */
-    T *operator->()
+    T *operator->() const
     {
         return get();
     }
@@ -118,15 +118,15 @@ struct SingletonPtr {
      * @returns
      *   A reference to the singleton
      */
-    T &operator*()
+    T &operator*() const
     {
         return *get();
     }
 
     // This is zero initialized when in global scope
-    T *_ptr;
+    mutable T *_ptr;
     // Force data to be 4 byte aligned
-    uint32_t _data[(sizeof(T) + sizeof(uint32_t) - 1) / sizeof(uint32_t)];
+    mutable uint32_t _data[(sizeof(T) + sizeof(uint32_t) - 1) / sizeof(uint32_t)];
 };
 
 #endif

From e7815c64ad8878dad3bf4db425b59c3f466a6bc5 Mon Sep 17 00:00:00 2001
From: Kevin Bracey <kevin.bracey@arm.com>
Date: Mon, 10 Sep 2018 11:10:41 +0300
Subject: [PATCH 2/2] Align SingletonPtr data to 8 bytes, or use C++11

Be more cautious about alignment - align the data within a SingletonPtr
to 8 bytes rather than 4. This could increase padding overhead by up
to 8 bytes, sadly, but we may need this alignment for correct operation.

Conditional check added for C++11 - if in use we can get correct minimal
alignment by using alignas(T).
---
 platform/SingletonPtr.h | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/platform/SingletonPtr.h b/platform/SingletonPtr.h
index 57fc76b154..595d9807ca 100644
--- a/platform/SingletonPtr.h
+++ b/platform/SingletonPtr.h
@@ -125,8 +125,13 @@ struct SingletonPtr {
 
     // This is zero initialized when in global scope
     mutable T *_ptr;
-    // Force data to be 4 byte aligned
-    mutable uint32_t _data[(sizeof(T) + sizeof(uint32_t) - 1) / sizeof(uint32_t)];
+#if __cplusplus >= 201103L
+    // Align data appropriately
+    alignas(T) mutable char _data[sizeof(T)];
+#else
+    // Force data to be 8 byte aligned
+    mutable uint64_t _data[(sizeof(T) + sizeof(uint64_t) - 1) / sizeof(uint64_t)];
+#endif
 };
 
 #endif