move doubleCheckedInit() to a comphelper header file

For further reuse in more source files.

Change-Id: I2fcbb98a81725e14d6d433f62622d2c48d146de1
Reviewed-on: https://gerrit.libreoffice.org/55763
Tested-by: Jenkins
Reviewed-by: Michael Meeks <michael.meeks@collabora.com>

include/comphelper/doublecheckedinit.hxx

+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+/*
+ * This file is part of the LibreOffice project.
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/.
+ *
+ * This file incorporates work covered by the following license notice:
+ *
+ *   Licensed to the Apache Software Foundation (ASF) under one or more
+ *   contributor license agreements. See the NOTICE file distributed
+ *   with this work for additional information regarding copyright
+ *   ownership. The ASF licenses this file to you under the Apache
+ *   License, Version 2.0 (the "License"); you may not use this file
+ *   except in compliance with the License. You may obtain a copy of
+ *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
+ */
+
+#ifndef INCLUDED_COMPHELPER_DOUBLECHECKEDINIT_HXX
+#define INCLUDED_COMPHELPER_DOUBLECHECKEDINIT_HXX
+
+#include <osl/getglobalmutex.hxx>
+
+#include <atomic>
+// HACK: <atomic> includes <stdbool.h>, which in some Clang versions does '#define bool bool',
+// which confuses clang plugins.
+#undef bool
+#include <functional>
+
+namespace comphelper
+{
+/**
+ * Thread-safe singleton creation.
+ *
+ * It is normally sufficient to create singletons using static variables in a function.
+ * This function is only for use cases that have a more complex lifetime of the object,
+ * such as when the object may require specific cleanup or may be created more times
+ * (e.g. when there is a "singleton" per each instance of another object).
+ */
+template <typename Type, typename Function = std::function<Type*()>,
+          typename Guard = osl::MutexGuard, typename GuardCtor = osl::GetGlobalMutex>
+static inline Type* doubleCheckedInit(std::atomic<Type*>& pointer, Function function,
+                                      GuardCtor guardCtor = osl::GetGlobalMutex())
+{
+    Type* p = pointer.load(std::memory_order_acquire);
+    if (!p)
+    {
+        Guard guard(guardCtor());
+        p = pointer.load(std::memory_order_relaxed);
+        if (!p)
+        {
+            p = function();
+            pointer.store(p, std::memory_order_release);
+        }
+    }
+    return p;
+}
+
+} // namespace
+
+#endif // INCLUDED_COMPHELPER_DOUBLECHECKEDINIT_HXX
+
+/* vim:set shiftwidth=4 softtabstop=4 expandtab: */

sc/source/core/data/global.cxx

@@ -47,6 +47,7 @@
 
 #include <i18nlangtag/mslangid.hxx>
 #include <com/sun/star/lang/Locale.hpp>
+#include <comphelper/doublecheckedinit.hxx>
 #include <comphelper/processfactory.hxx>
 #include <comphelper/string.hxx>
 #include <unotools/calendarwrapper.hxx>
@@ -126,28 +127,6 @@ sal_uInt16 nScFillModeMouseModifier = 0; //FIXME: And this
 
 bool ScGlobal::bThreadedGroupCalcInProgress = false;
 
-// Thread-safe singleton creation. Ideally rtl_Instance should be used, but that one doesn't
-// allow accessing the pointer (so ScGlobal::Clear() cannot free the objects). So this function
-// is basically rtl_Instance::create() that uses a given pointer.
-template< typename Type, typename Function = std::function< Type*() >,
-          typename Guard = osl::MutexGuard, typename GuardCtor = osl::GetGlobalMutex >
-static inline
-Type* doubleCheckedInit( std::atomic<Type*>& pointer, Function function, GuardCtor guardCtor = osl::GetGlobalMutex())
-{
-    Type* p = pointer.load( std::memory_order_acquire );
-    if (!p)
-    {
-        Guard guard(guardCtor());
-        p = pointer.load( std::memory_order_relaxed );
-        if (!p)
-        {
-            p = function();
-            pointer.store( p, std::memory_order_release );
-        }
-    }
-    return p;
-}
-
 // Static functions
 
 bool ScGlobal::HasAttrChanged( const SfxItemSet&  rNewAttrs,
@@ -299,12 +278,12 @@ ScAutoFormat* ScGlobal::GetOrCreateAutoFormat()
 
 LegacyFuncCollection* ScGlobal::GetLegacyFuncCollection()
 {
-    return doubleCheckedInit( pLegacyFuncCollection, []() { return new LegacyFuncCollection(); });
+    return comphelper::doubleCheckedInit( pLegacyFuncCollection, []() { return new LegacyFuncCollection(); });
 }
 
 ScUnoAddInCollection* ScGlobal::GetAddInCollection()
 {
-    return doubleCheckedInit( pAddInCollection, []() { return new ScUnoAddInCollection(); });
+    return comphelper::doubleCheckedInit( pAddInCollection, []() { return new ScUnoAddInCollection(); });
 }
 
 ScUserList* ScGlobal::GetUserList()
@@ -999,7 +978,7 @@ void ScGlobal::AddLanguage( SfxItemSet& rSet, const SvNumberFormatter& rFormatte
 
 utl::TransliterationWrapper* ScGlobal::GetpTransliteration()
 {
-    return doubleCheckedInit( pTransliteration,
+    return comphelper::doubleCheckedInit( pTransliteration,
         []()
         {
             const LanguageType eOfficeLanguage = Application::GetSettings().GetLanguageTag().getLanguageType();
@@ -1011,7 +990,7 @@ utl::TransliterationWrapper* ScGlobal::GetpTransliteration()
 }
 ::utl::TransliterationWrapper* ScGlobal::GetCaseTransliteration()
 {
-    return doubleCheckedInit( pCaseTransliteration,
+    return comphelper::doubleCheckedInit( pCaseTransliteration,
         []()
         {
             const LanguageType eOfficeLanguage = Application::GetSettings().GetLanguageTag().getLanguageType();
@@ -1041,7 +1020,7 @@ CalendarWrapper*     ScGlobal::GetCalendar()
 }
 CollatorWrapper*        ScGlobal::GetCollator()
 {
-    return doubleCheckedInit( pCollator,
+    return comphelper::doubleCheckedInit( pCollator,
         []()
         {
             CollatorWrapper* p = new CollatorWrapper( ::comphelper::getProcessComponentContext() );
@@ -1051,7 +1030,7 @@ CollatorWrapper*        ScGlobal::GetCollator()
 }
 CollatorWrapper*        ScGlobal::GetCaseCollator()
 {
-    return doubleCheckedInit( pCaseCollator,
+    return comphelper::doubleCheckedInit( pCaseCollator,
         []()
         {
             CollatorWrapper* p = new CollatorWrapper( ::comphelper::getProcessComponentContext() );
@@ -1061,7 +1040,7 @@ CollatorWrapper*        ScGlobal::GetCaseCollator()
 }
 css::lang::Locale*     ScGlobal::GetLocale()
 {
-    return doubleCheckedInit( pLocale,
+    return comphelper::doubleCheckedInit( pLocale,
         []() { return new css::lang::Locale( Application::GetSettings().GetLanguageTag().getLocale()); });
 }