diff --git a/shell/languagecontroller.cpp b/shell/languagecontroller.cpp
index 817c1ceac4..0dec98614a 100644
--- a/shell/languagecontroller.cpp
+++ b/shell/languagecontroller.cpp
@@ -1,385 +1,389 @@
 /***************************************************************************
  *   Copyright 2006 Adam Treat <treat@kde.org>                             *
  *   Copyright 2007 Alexander Dymo <adymo@kdevelop.org>                    *
  *                                                                         *
  *   This program is free software; you can redistribute it and/or modify  *
  *   it under the terms of the GNU Library General Public License as       *
  *   published by the Free Software Foundation; either version 2 of the    *
  *   License, or (at your option) any later version.                       *
  *                                                                         *
  *   This program is distributed in the hope that it will be useful,       *
  *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
  *   GNU General Public License for more details.                          *
  *                                                                         *
  *   You should have received a copy of the GNU Library General Public     *
  *   License along with this program; if not, write to the                 *
  *   Free Software Foundation, Inc.,                                       *
  *   51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.         *
  ***************************************************************************/
 #include "languagecontroller.h"
 
 #include <QHash>
 #include <QMutexLocker>
 
 #include <kmimetype.h>
 
 #include <interfaces/idocument.h>
 #include <interfaces/idocumentcontroller.h>
 #include <interfaces/iplugin.h>
 #include <interfaces/iplugincontroller.h>
 #include <language/assistant/staticassistantsmanager.h>
 #include <language/interfaces/ilanguagesupport.h>
 #include <language/backgroundparser/backgroundparser.h>
 #include <language/duchain/duchain.h>
 
 #include "core.h"
 #include "language.h"
 #include "settings/ccpreferences.h"
 #include "completionsettings.h"
 #include <QThread>
 
 namespace {
 // Maximum length of a string to still consider it as a file extension which we cache
 // This has to be a slow value, so that we don't fill our file extension cache with crap
 const int maximumCacheExtensionLength = 3;
 
 // TODO: kf5, use QStringLiteral
 const QString KEY_SupportedMimeTypes = "X-KDevelop-SupportedMimeTypes";
 const QString KEY_ILanguageSupport = "ILanguageSupport";
 }
 
 namespace KDevelop {
 
 
 typedef QHash<QString, ILanguage*> LanguageHash;
 typedef QHash<QString, QList<ILanguage*> > LanguageCache;
 
 struct LanguageControllerPrivate {
     LanguageControllerPrivate(LanguageController *controller)
         : dataMutex(QMutex::Recursive)
         , backgroundParser(new BackgroundParser(controller))
         , staticAssistantsManager(new StaticAssistantsManager(controller))
         , m_cleanedUp(false)
         , m_controller(controller)
     {}
 
     void documentActivated(KDevelop::IDocument *document)
     {
         KUrl url = document->url();
         if (!url.isValid()) {
             return;
         }
 
         foreach (ILanguage *lang, activeLanguages) {
             lang->deactivate();
         }
 
         activeLanguages.clear();
 
         QList<ILanguage*> languages = m_controller->languagesForUrl(url);
         foreach (ILanguage *lang, languages) {
             lang->activate();
             activeLanguages << lang;
         }
     }
 
     QList<ILanguage*> activeLanguages;
 
     mutable QMutex dataMutex;
     
     LanguageHash languages; //Maps language-names to languages
     LanguageCache languageCache; //Maps mimetype-names to languages
     typedef QMultiMap<KMimeType::Ptr, ILanguage*> MimeTypeCache;
     MimeTypeCache mimeTypeCache; //Maps mimetypes to languages
     // fallback cache for file extensions not handled by any pattern
     typedef QMap<QString, QList<ILanguage*> > FileExtensionCache;
     FileExtensionCache fileExtensionCache;
 
     BackgroundParser *backgroundParser;
     StaticAssistantsManager* staticAssistantsManager;
     bool m_cleanedUp;
     
     ILanguage* addLanguageForSupport(ILanguageSupport* support, const QStringList& mimetypes);
     ILanguage* addLanguageForSupport(ILanguageSupport* support);
 
 private:
     LanguageController *m_controller;
 };
 
 ILanguage* LanguageControllerPrivate::addLanguageForSupport(ILanguageSupport* languageSupport,
                                                             const QStringList& mimetypes)
 {
     Q_ASSERT(!languages.contains(languageSupport->name()));
 
     ILanguage* ret = new Language(languageSupport, m_controller);
     languages.insert(languageSupport->name(), ret);
 
     foreach(const QString& mimeTypeName, mimetypes) {
         kDebug(9505) << "adding supported mimetype:" << mimeTypeName << "language:" << languageSupport->name();
         languageCache[mimeTypeName] << ret;
         KMimeType::Ptr mime = KMimeType::mimeType(mimeTypeName);
         if(mime) {
             mimeTypeCache.insert(mime, ret);
         } else {
             kWarning() << "could not create mime-type" << mimeTypeName;
         }
     }
 
     return ret;
 }
 
 ILanguage* LanguageControllerPrivate::addLanguageForSupport(KDevelop::ILanguageSupport* languageSupport)
 {
     if(languages.contains(languageSupport->name()))
         return languages[languageSupport->name()];
 
     Q_ASSERT(dynamic_cast<IPlugin*>(languageSupport));
 
     QVariant mimetypes = Core::self()->pluginController()->pluginInfo(dynamic_cast<IPlugin*>(languageSupport)).property(KEY_SupportedMimeTypes);
 
     return addLanguageForSupport(languageSupport, mimetypes.toStringList());
 }
 
 LanguageController::LanguageController(QObject *parent)
     : ILanguageController(parent)
 {
     setObjectName("LanguageController");
     d = new LanguageControllerPrivate(this);
 }
 
 LanguageController::~LanguageController()
 {
     delete d;
 }
 
 void LanguageController::initialize()
 {
     d->backgroundParser->loadSettings();
 
     // make sure the DUChain is setup before we try to access it from different threads at the same time
     DUChain::self();
 
     connect(Core::self()->documentController(), SIGNAL(documentActivated(KDevelop::IDocument*)),
             SLOT(documentActivated(KDevelop::IDocument*)));
 }
 
 void LanguageController::cleanup()
 {
     QMutexLocker lock(&d->dataMutex);
     d->m_cleanedUp = true;
 }
 
 QList<ILanguage*> LanguageController::activeLanguages()
 {
     QMutexLocker lock(&d->dataMutex);
     
     return d->activeLanguages;
 }
 
 StaticAssistantsManager* LanguageController::staticAssistantsManager() const
 {
     return d->staticAssistantsManager;
 }
 
 ICompletionSettings *LanguageController::completionSettings() const {
     return &CompletionSettings::self();
 }
 
 QList<ILanguage*> LanguageController::loadedLanguages() const
 {
     QMutexLocker lock(&d->dataMutex);
     QList<ILanguage*> ret;
     
     if(d->m_cleanedUp)
         return ret;
     
     foreach(ILanguage* lang, d->languages)
         ret << lang;
     return ret;
 }
 
 ILanguage *LanguageController::language(const QString &name) const
 {
     QMutexLocker lock(&d->dataMutex);
     
     if(d->m_cleanedUp)
         return 0;
     
     if(d->languages.contains(name))
         return d->languages[name];
     else{
         ILanguage* ret = 0;
         QVariantMap constraints;
         constraints.insert("X-KDevelop-Language", name);
         QList<IPlugin*> supports = Core::self()->pluginController()->allPluginsForExtension(KEY_ILanguageSupport, constraints);
         if(!supports.isEmpty()) {
             ILanguageSupport *languageSupport = supports[0]->extension<ILanguageSupport>();
             if(supports[0])
                 ret = d->addLanguageForSupport(languageSupport);
         }
         return ret;
     }
 }
 
 bool isNumeric(const QString& str)
 {
     int len = str.length();
     if(len == 0)
         return false;
     for(int a = 0; a < len; ++a)
         if(!str[a].isNumber())
             return false;
     return true;
 }
 
 QList<ILanguage*> LanguageController::languagesForUrl(const KUrl &url)
 {
     QMutexLocker lock(&d->dataMutex);
     
     QList<ILanguage*> languages;
     
     if(d->m_cleanedUp)
         return languages;
     
     const QString fileName = url.fileName();
 
     ///TODO: cache regexp or simple string pattern for endsWith matching
     QRegExp exp("", Qt::CaseInsensitive, QRegExp::Wildcard);
     ///non-crashy part: Use the mime-types of known languages
     for(LanguageControllerPrivate::MimeTypeCache::const_iterator it = d->mimeTypeCache.constBegin();
         it != d->mimeTypeCache.constEnd(); ++it)
     {
         foreach(const QString& pattern, it.key()->patterns()) {
             if(pattern.startsWith('*')) {
                 const QStringRef subPattern = pattern.midRef(1);
                 if (!subPattern.contains('*')) {
                     //optimize: we can skip the expensive QRegExp in this case
                     //and do a simple string compare (much faster)
                     if (fileName.endsWith(subPattern)) {
                         languages << *it;
                     }
                     continue;
                 }
             }
 
             exp.setPattern(pattern);
             if(int position = exp.indexIn(fileName)) {
                 if(position != -1 && exp.matchedLength() + position == fileName.length())
                     languages << *it;
             }
         }
     }
 
     if(!languages.isEmpty())
         return languages;
 
     // no pattern found, try the file extension cache
     int extensionStart = fileName.lastIndexOf(QLatin1Char('.'));
     QString extension;
     if(extensionStart != -1)
     {
         extension = fileName.mid(extensionStart+1);
         if(extension.size() > maximumCacheExtensionLength || isNumeric(extension))
             extension = QString();
     }
 
     if(!extension.isEmpty())
     {
         languages = d->fileExtensionCache.value(extension);
         if(languages.isEmpty() && d->fileExtensionCache.contains(extension))
             return languages; // Nothing found, but was in the cache
     }
 
     //Never use findByUrl from within a background thread, and never load a language support
     //from within the backgruond thread. Both is unsafe, and can lead to crashes
     if(!languages.isEmpty() || QThread::currentThread() != thread())
         return languages;
 
     KMimeType::Ptr mimeType;
-    
+
+    int accuracy = 0;
     if(!extension.isEmpty()) {
         // If we have recognized a file extension, allow using the file-contents
         // to look up the type. We will cache it after all.
-        mimeType = KMimeType::findByUrl(url);
+        mimeType = KMimeType::findByUrl(url, 0, false, false, &accuracy);
     } else {
         // If we have not recognized a file extension, do not allow using the file-contents
         // to look up the type. We cannot cache the result, and thus we might end up reading
         // the contents of every single file, which can make the application very unresponsive.
         mimeType = KMimeType::findByUrl(url, 0, false, true);
 
         if (mimeType->isDefault()) {
             // ask the document controller about a more concrete mimetype
             IDocument* doc = ICore::self()->documentController()->documentForUrl(url);
             if (doc) {
                 mimeType = doc->mimeType();
             }
         }
     }
 
     languages = languagesForMimetype(mimeType->name());
 
-    if(!extension.isEmpty())
+    // E.g. because  of some txt file that begins with /* and considered as c++ file
+    // we don't want the c++ language support to parse all txt files.
+    if(!extension.isEmpty() && accuracy > 80) {
         d->fileExtensionCache.insert(extension, languages);
+    }
 
     return languages;
 }
 
 QList<ILanguage*> LanguageController::languagesForMimetype(const QString& mimetype)
 {
     QMutexLocker lock(&d->dataMutex);
 
     QList<ILanguage*> languages;
     LanguageCache::ConstIterator it = d->languageCache.constFind(mimetype);
     if (it != d->languageCache.constEnd()) {
         languages = it.value();
     } else {
         QVariantMap constraints;
         constraints.insert(KEY_SupportedMimeTypes, mimetype);
         QList<IPlugin*> supports = Core::self()->pluginController()->allPluginsForExtension(KEY_ILanguageSupport, constraints);
 
         if (supports.isEmpty()) {
             kDebug(9505) << "no languages for mimetype:" << mimetype;
             d->languageCache.insert(mimetype, QList<ILanguage*>());
         } else {
             foreach (IPlugin *support, supports) {
                 ILanguageSupport* languageSupport = support->extension<ILanguageSupport>();
                 kDebug(9505) << "language-support:" << languageSupport;
                 if(languageSupport)
                     languages << d->addLanguageForSupport(languageSupport);
             }
         }
     }
     return languages;
 }
 
 QList<QString> LanguageController::mimetypesForLanguageName(const QString& languageName)
 {
     QMutexLocker lock(&d->dataMutex);
 
     QList<QString> mimetypes;
     for (LanguageCache::ConstIterator iter = d->languageCache.constBegin(); iter != d->languageCache.constEnd(); ++iter) {
         foreach (ILanguage* language, iter.value()) {
             if (language->name() == languageName) {
                 mimetypes << iter.key();
                 break;
             }
         }
     }
     return mimetypes;
 }
 
 BackgroundParser *LanguageController::backgroundParser() const
 {
     return d->backgroundParser;
 }
 
 void LanguageController::addLanguageSupport(ILanguageSupport* languageSupport, const QStringList& mimetypes)
 {
     d->addLanguageForSupport(languageSupport, mimetypes);
 }
 
 }
 
 #include "languagecontroller.moc"