From be87822a361ece714b99b89e41d3b64a5cd41402 Mon Sep 17 00:00:00 2001
From: Nikola Kosturski <nikola.kosturski@shelly.com>
Date: Fri, 12 Jul 2024 12:45:44 +0300
Subject: [PATCH] Add CHIP_CONFIG_DYNAMIC_GLOBALS option to enable dynamic
 allocation of Global<T>s

---
 src/app/reporting/ReportSchedulerImpl.h |  6 ++--
 src/lib/core/CHIPConfig.h               | 12 ++++++++
 src/lib/core/Global.h                   | 41 +++++++++++++++++++------
 src/platform/Linux/CHIPPlatformConfig.h |  6 ++++
 4 files changed, 52 insertions(+), 13 deletions(-)

diff --git a/src/app/reporting/ReportSchedulerImpl.h b/src/app/reporting/ReportSchedulerImpl.h
index ff72eecc8c2de6..87a1f7f4faa555 100644
--- a/src/app/reporting/ReportSchedulerImpl.h
+++ b/src/app/reporting/ReportSchedulerImpl.h
@@ -73,7 +73,7 @@ class ReportSchedulerImpl : public ReportScheduler
      *        solely based on its ReadHandler's state. Therefore, no synchronization action on the ICDState is needed in this
      *        implementation.
      */
-    void OnTransitionToIdle() override {};
+    void OnTransitionToIdle() override{};
 
     /**
      * @brief When the ICD transitions to Active mode, this implementation will trigger a report emission on each ReadHandler that
@@ -88,13 +88,13 @@ class ReportSchedulerImpl : public ReportScheduler
      * @brief Similar to the OnTransitionToIdle() method, this implementation does not attempt any synchronization on ICD events,
      *        therefore no action is needed on the ICDModeChange() method.
      */
-    void OnICDModeChange() override {};
+    void OnICDModeChange() override{};
 
     /**
      * @brief This implementation does not attempt any synchronization on this ICD event, therefore no action is needed on
      * ICDEnterIdleMode()
      */
-    void OnEnterIdleMode() override {};
+    void OnEnterIdleMode() override{};
 
     // ReadHandlerObserver
 
diff --git a/src/lib/core/CHIPConfig.h b/src/lib/core/CHIPConfig.h
index e9c317dfc79d5c..c8c8fdc66ebf5e 100644
--- a/src/lib/core/CHIPConfig.h
+++ b/src/lib/core/CHIPConfig.h
@@ -187,6 +187,18 @@
 #define CHIP_CONFIG_GLOBALS_NO_DESTRUCT 0
 #endif // CHIP_CONFIG_GLOBALS_NO_DESTRUCT
 
+/**
+ *  @def CHIP_CONFIG_DYNAMIC_GLOBALS
+ *
+ *  @brief
+ *    Whether to use dynamic allocation for chip::Global objects.
+ *
+ *    The default is to use static allocation.
+ */
+#ifndef CHIP_CONFIG_DYNAMIC_GLOBALS
+#define CHIP_CONFIG_DYNAMIC_GLOBALS 0
+#endif // CHIP_CONFIG_DYNAMIC_GLOBALS
+
 /**
  *  @def CHIP_CONFIG_SHA256_CONTEXT_SIZE
  *
diff --git a/src/lib/core/Global.h b/src/lib/core/Global.h
index c5fe3739b8fec5..3573998ade8d47 100644
--- a/src/lib/core/Global.h
+++ b/src/lib/core/Global.h
@@ -85,13 +85,12 @@ class Global
     /// NOT thread-safe, external synchronization is required.
     T & get() { return _get(); }
     T * operator->() { return &_get(); }
-
-    template <class U = typename std::remove_extent<T>::type>
+    template <class U = std::remove_extent_t<T>>
     U & operator[](std::size_t i)
     {
         return _get()[i];
     }
-    template <std::size_t N = std::extent<T>::value>
+    template <std::size_t N = std::extent_v<T>>
     constexpr std::size_t size() const
     {
         return N;
@@ -110,17 +109,28 @@ class Global
 private:
     // Zero-initialize everything. We should technically leave mStorage uninitialized,
     // but that can sometimes cause clang to be unable to constant-initialize the object.
+#if CHIP_CONFIG_DYNAMIC_GLOBALS
+    unsigned char * mStorage = nullptr;
+#else
     alignas(T) unsigned char mStorage[sizeof(T)] = {};
+#endif // CHIP_CONFIG_DYNAMIC_GLOBALS
     OnceStrategy mOnce;
 
     T & _get()
     {
-        T * value = reinterpret_cast<T *>(mStorage);
-        mOnce.call(&create, value);
-        return *value;
+#if CHIP_CONFIG_DYNAMIC_GLOBALS
+        mOnce.call(&create, &mStorage);
+#else
+        mOnce.call(&create, mStorage);
+#endif // CHIP_CONFIG_DYNAMIC_GLOBALS
+        return *reinterpret_cast<T *>(mStorage);
     }
     static void create(void * value)
     {
+#if CHIP_CONFIG_DYNAMIC_GLOBALS
+        unsigned char ** storage = static_cast<unsigned char **>(value);
+        value = *storage = new unsigned char[sizeof(T)];
+#endif // CHIP_CONFIG_DYNAMIC_GLOBALS
         new (value) T();
 #if !CHIP_CONFIG_GLOBALS_NO_DESTRUCT
         CHIP_CXA_ATEXIT(&destroy, value);
@@ -128,17 +138,28 @@ class Global
     }
 
     template <class U, std::size_t N>
-    static void destroy(U (*value)[N])
+    static void _destroy(U (*value)[N])
+    {
+        _destroy_array(*value, N);
+    }
+    template <class U>
+    static void _destroy_array(U * array, std::size_t N)
     {
         for (std::size_t i = 0; i < N; ++i)
-            destroy(value[i]);
+            array[i].~U();
     }
     template <class U>
-    static void destroy(U * value)
+    static void _destroy(U * value)
     {
         value->~U();
     }
-    static void destroy(void * value) { destroy(static_cast<T *>(value)); }
+    static void destroy(void * value)
+    {
+        _destroy(static_cast<T *>(value));
+#if CHIP_CONFIG_DYNAMIC_GLOBALS
+        delete[] static_cast<unsigned char *>(value);
+#endif // CHIP_CONFIG_DYNAMIC_GLOBALS
+    }
 
 #else // CHIP_CONFIG_GLOBALS_LAZY_INIT
 public:
diff --git a/src/platform/Linux/CHIPPlatformConfig.h b/src/platform/Linux/CHIPPlatformConfig.h
index 9e2832307f27b2..7eb102b1a6c122 100644
--- a/src/platform/Linux/CHIPPlatformConfig.h
+++ b/src/platform/Linux/CHIPPlatformConfig.h
@@ -27,6 +27,12 @@
 
 #define CHIP_CONFIG_ABORT() abort()
 
+extern "C" int __cxa_atexit(void (*func)(void *), void * arg, void * d);
+#define CHIP_CXA_ATEXIT(f, p) __cxa_atexit((f), (p), nullptr)
+
+#define CHIP_CONFIG_DYNAMIC_GLOBALS 1
+#define CHIP_CONFIG_GLOBALS_LAZY_INIT 1
+
 using CHIP_CONFIG_PERSISTED_STORAGE_KEY_TYPE = const char *;
 #define CHIP_CONFIG_PERSISTED_STORAGE_MAX_KEY_LENGTH 16