[LyX/master] Make theWordList() thread safe.

[Georg Baum]

commit cf89851374163be2e8a390dd917d7ef435978979
Author: Georg Baum <b...@lyx.org>
Date:   Fri Jul 4 22:19:43 2014 +0200

    Make theWordList() thread safe.
    
    Without this, you get crashes in a few second when you set the autosave
    interval to one second and edit quickly (typing new words etc). The reason
    is that the cloned buffer wants to insert words into the word list and
    remove them again, but it lives in a different thread.

diff --git a/src/WordList.cpp b/src/WordList.cpp
index 3a095af..16f3b92 100644
--- a/src/WordList.cpp
+++ b/src/WordList.cpp
@@ -18,6 +18,8 @@
 #include "support/lassert.h"
 #include "support/weighted_btree.h"
 
+#include <QThreadStorage>
+
 #include <map>
 
 using namespace std;
@@ -26,26 +28,37 @@ namespace lyx {
 
 ///
 typedef map<string, WordList *> GlobalWordList;
-GlobalWordList theGlobalWordList;
+// Each thread uses its own word list, but only the one of the GUI thread is
+// used to do real work. The others are only neded to prevent simultanous
+// write access e.g. from a cloned buffer and a true document buffer.
+QThreadStorage<GlobalWordList *> theGlobalWordList;
 
 
 WordList * theWordList(string const & lang)
 {
-       GlobalWordList::iterator it = theGlobalWordList.find(lang);
-       if (it != theGlobalWordList.end())
+       if (!theGlobalWordList.hasLocalData())
+               theGlobalWordList.setLocalData(new GlobalWordList);
+       GlobalWordList * globalWordList = theGlobalWordList.localData();
+       GlobalWordList::iterator it = globalWordList->find(lang);
+       if (it != globalWordList->end())
                return it->second;
-       else
-               theGlobalWordList[lang] = new WordList;
-       return theGlobalWordList[lang];
+       else {
+               WordList * wl = new WordList;
+               (*globalWordList)[lang] = wl;
+               return wl;
+       }
 }
 
 
 void WordList::cleanupWordLists()
 {
-       GlobalWordList::const_iterator it = theGlobalWordList.begin();
-       for (; it != theGlobalWordList.end(); ++it)
+       if (!theGlobalWordList.hasLocalData())
+               return;
+       GlobalWordList * globalWordList = theGlobalWordList.localData();
+       GlobalWordList::const_iterator it = globalWordList->begin();
+       for (; it != globalWordList->end(); ++it)
                delete it->second;
-       theGlobalWordList.clear();
+       globalWordList->clear();
 }