TQRegExp: fix engine cache destruction ordering

In case there are static TQRegExp instances the regexp engine cash might
be destroyed before them; hence we need some special handling of
construction/destruction of the cache object(s).

Closes: https://mirror.git.trinitydesktop.org/gitea/TDE/tqt3/issues/142
Signed-off-by: Alexander Golubev <fatzer2@gmail.com>

src/tools/qregexp.cpp

@@ -3211,39 +3211,86 @@ struct TQRegExpPrivate
 };
 
 #ifndef TQT_NO_REGEXP_OPTIM
-static TQSingleCleanupHandler<TQCache<TQRegExpEngine> > cleanup_cache;
-#  ifndef TQT_THREAD_SUPPORT
-static TQCache<TQRegExpEngine> *engineCache = 0;
+namespace {
+
+// Due to regexpEngine() is called from destructors (including destructors of static TQRegExp
+// instances) it may cause it to try to resurrect the engine cache after it's been already
+// destroyed, so we should keep an eye on it, hence we have a somewhat peculiar singleton here
+// Yay! Handling destruction of statics is so much fun! >_<
+class EngineCacheKeaper {
+public:
+    static TQCache<TQRegExpEngine> *getCache() {
+	if ( wasDestroyed ) {
+	    return nullptr;
+	}
+
+	static EngineCacheKeaper self;
+	return self.doGetCache();
+    }
+private:
+
+    TQCache<TQRegExpEngine> *doGetCache() {
+#  ifdef TQT_THREAD_SUPPORT
+	TQThreadInstance *currentThread = TQThreadInstance::current();
+	if (!currentThread) {
+	    return nullptr;
+	}
+	TQCache<TQRegExpEngine> *engineCache = engineCaches.localData();
+#  endif // TQT_THREAD_SUPPORT
+
+	if ( engineCache == 0 ) {
+	    engineCache = new TQCache<TQRegExpEngine>;
+	    engineCache->setAutoDelete( TRUE );
+#  ifdef TQT_THREAD_SUPPORT
+	    engineCaches.setLocalData(engineCache);
+#  else
+	    static TQSingleCleanupHandler<TQCache<TQRegExpEngine>> cleanup_cache;
+	    cleanup_cache.set( &engineCache );
+#  endif // !TQT_THREAD_SUPPORT
+	}
+
+	return engineCache;
+    }
+
+#  ifdef TQT_THREAD_SUPPORT
+    TQThreadStorage<TQCache<TQRegExpEngine>*> engineCaches;
+#  else
+    TQCache<TQRegExpEngine> *engineCache;
 #  endif // TQT_THREAD_SUPPORT
+
+    ~EngineCacheKeaper() {
+	wasDestroyed = TRUE;
+#  if !defined(TQT_THREAD_SUPPORT)
+	delete engineCache;
+#  endif // !defined(TQT_THREAD_SUPPORT)
+    }
+    static bool wasDestroyed;
+};
+
+bool EngineCacheKeaper::wasDestroyed = 0;
+
+}
 #endif // TQT_NO_REGEXP_OPTIM
 
+
 static void regexpEngine( TQRegExpEngine *&eng, const TQString &pattern,
 			  bool caseSensitive, bool deref )
 {
-#  ifdef TQT_THREAD_SUPPORT
-    static TQThreadStorage<TQCache<TQRegExpEngine> *> engineCaches;
-    TQCache<TQRegExpEngine> *engineCache = 0;
-    TQThreadInstance *currentThread = TQThreadInstance::current();
-    if (currentThread)
-        engineCache = engineCaches.localData();
-#endif // TQT_THREAD_SUPPORT
+#ifndef TQT_NO_REGEXP_OPTIM
+    TQCache<TQRegExpEngine> *engineCache = EngineCacheKeaper::getCache();
+#endif // TQT_NO_REGEXP_OPTIM
 
     if ( !deref ) {
 #ifndef TQT_NO_REGEXP_OPTIM
-#  ifdef TQT_THREAD_SUPPORT
-        if ( currentThread )
-#  endif
-            {
-                if ( engineCache != 0 ) {
-                    eng = engineCache->take( pattern );
-                    if ( eng == 0 || eng->caseSensitive() != caseSensitive ) {
-                        delete eng;
-                    } else {
-                        eng->ref();
-                        return;
-                    }
-                }
-            }
+        if ( engineCache ) {
+	    eng = engineCache->take( pattern );
+	    if ( eng == 0 || eng->caseSensitive() != caseSensitive ) {
+		delete eng;
+	    } else {
+		eng->ref();
+		return;
+	    }
+	}
 #endif // TQT_NO_REGEXP_OPTIM
 	eng = new TQRegExpEngine( pattern, caseSensitive );
 	return;
@@ -3251,23 +3298,11 @@ static void regexpEngine( TQRegExpEngine *&eng, const TQString &pattern,
 
     if ( eng->deref() ) {
 #ifndef TQT_NO_REGEXP_OPTIM
-#  ifdef TQT_THREAD_SUPPORT
-        if ( currentThread )
-#  endif
-            {
-                if ( engineCache == 0 ) {
-                    engineCache = new TQCache<TQRegExpEngine>;
-                    engineCache->setAutoDelete( TRUE );
-#  ifdef TQT_THREAD_SUPPORT
-                    engineCaches.setLocalData(engineCache);
-#  else
-                    cleanup_cache.set( &engineCache );
-#  endif // !TQT_THREAD_SUPPORT
-                }
-                if ( !pattern.isNull() &&
-                     engineCache->insert(pattern, eng, 4 + pattern.length() / 4) )
-                    return;
-            }
+	if ( engineCache ) {
+	    if ( !pattern.isNull() &&
+	         engineCache->insert(pattern, eng, 4 + pattern.length() / 4) )
+		return;
+	}
 #else
 	Q_UNUSED( pattern );
 #endif // TQT_NO_REGEXP_OPTIM