8.4

1 files changed, 57 insertions, 0 deletions

diff --git a/zen/globals.h b/zen/globals.h
new file mode 100644
index 00000000..5f3dd64a
--- /dev/null
+++ b/zen/globals.h
@@ -0,0 +1,57 @@
+// *****************************************************************************
+// * This file is part of the FreeFileSync project. It is distributed under    *
+// * GNU General Public License: http://www.gnu.org/licenses/gpl-3.0           *
+// * Copyright (C) Zenju (zenju AT freefilesync DOT org) - All Rights Reserved *
+// *****************************************************************************
+
+#ifndef GLOBALS_H_8013740213748021573485
+#define GLOBALS_H_8013740213748021573485
+
+#include <atomic>
+#include <memory>
+#include "scope_guard.h"
+
+namespace zen
+{
+//solve static destruction order fiasco by providing scoped ownership and serialized access to global variables
+template <class T>
+class Global
+{
+public:
+	Global() {}
+	explicit Global(std::unique_ptr<T>&& newInst) { set(std::move(newInst)); }
+	~Global() { set(nullptr); }
+	
+    std::shared_ptr<T> get() //=> return std::shared_ptr to let instance life time be handled by caller (MT usage!)
+    {
+        while (spinLock.exchange(true)) ;
+        ZEN_ON_SCOPE_EXIT(spinLock = false);
+        if (inst)
+            return *inst;
+        return nullptr;
+    }
+
+    void set(std::unique_ptr<T>&& newInst)
+    {
+        std::shared_ptr<T>* tmpInst = nullptr;
+        if (newInst)
+            tmpInst = new std::shared_ptr<T>(std::move(newInst));
+        {
+            while (spinLock.exchange(true)) ;
+            ZEN_ON_SCOPE_EXIT(spinLock = false);
+            std::swap(inst, tmpInst);
+        }
+        delete tmpInst;
+    }
+
+private:
+    //avoid static destruction order fiasco: there may be accesses to "Global<T>::get()" during process shutdown
+    //e.g. show message in debug_minidump.cpp or some detached thread assembling an error message!
+    //=> use trivially-destructible POD only!!!
+    std::shared_ptr<T>* inst = nullptr;
+    //serialize access: can't use std::mutex because of non-trival destructor
+    std::atomic<bool> spinLock { false };
+};
+}
+
+#endif //GLOBALS_H_8013740213748021573485