diff --git a/RedPandaIDE/parser/cppparser.cpp b/RedPandaIDE/parser/cppparser.cpp
index cdad7f89..813fcc69 100644
--- a/RedPandaIDE/parser/cppparser.cpp
+++ b/RedPandaIDE/parser/cppparser.cpp
@@ -976,7 +976,7 @@ void CppParser::resetParser()
         mInlineNamespaces.clear();
 
         mPreprocessor.clear();
-        mTokenizer.reset();
+        mTokenizer.clear();
 
     }
 }
@@ -3260,8 +3260,7 @@ void CppParser::internalParse(const QString &fileName)
     // Preprocess the file...
     {
         auto action = finally([this]{
-            mPreprocessor.reset();
-            mTokenizer.reset();
+            mTokenizer.clear();
         });
         // Let the preprocessor augment the include records
 //        mPreprocessor.setIncludesList(mIncludesList);
@@ -3273,7 +3272,7 @@ void CppParser::internalParse(const QString &fileName)
 
         QStringList preprocessResult = mPreprocessor.result();
         //reduce memory usage
-        mPreprocessor.clearResult();
+        mPreprocessor.clearTempResults();
 #ifdef QT_DEBUG
 //        stringsToFile(mPreprocessor.result(),"r:\\preprocess.txt");
 //        mPreprocessor.dumpDefinesTo("r:\\defines.txt");
@@ -3301,7 +3300,7 @@ void CppParser::internalParse(const QString &fileName)
 //      mStatementList.dumpAll("r:\\all-stats.txt");
 #endif
         //reduce memory usage
-        mTokenizer.reset();
+        mTokenizer.clear();
     }
 }
 
diff --git a/RedPandaIDE/parser/cpppreprocessor.cpp b/RedPandaIDE/parser/cpppreprocessor.cpp
index a08d2bdb..59f36d9b 100644
--- a/RedPandaIDE/parser/cpppreprocessor.cpp
+++ b/RedPandaIDE/parser/cpppreprocessor.cpp
@@ -29,7 +29,7 @@ CppPreprocessor::CppPreprocessor()
 void CppPreprocessor::clear()
 {
     //don't use reset(), it will reset(add) defines.
-    clearResult();
+    clearTempResults();
 
     //Result across processings.
     //used by parser even preprocess finished
@@ -48,7 +48,7 @@ void CppPreprocessor::clear()
     mIncludePaths.clear();
 }
 
-void CppPreprocessor::clearResult()
+void CppPreprocessor::clearTempResults()
 {    
     //temporary data when preprocessing single file
     mFileName="";
@@ -159,13 +159,6 @@ PDefine CppPreprocessor::getHardDefine(const QString &name)
     return mHardDefines.value(name,PDefine());
 }
 
-void CppPreprocessor::reset()
-{
-    clearResult();
-    // Clear extracted data
-    resetDefines(); // do not throw away hardcoded
-}
-
 void CppPreprocessor::resetDefines()
 {
     mDefines = mHardDefines;
@@ -182,8 +175,9 @@ void CppPreprocessor::setScanOptions(bool parseSystem, bool parseLocal)
 
 void CppPreprocessor::preprocess(const QString &fileName, QStringList buffer)
 {
+    clearTempResults();
     mFileName = fileName;
-    reset();
+    mDefines = mHardDefines;
     openInclude(fileName, buffer);
     //    StringsToFile(mBuffer,"f:\\buffer.txt");
     preprocessBuffer();
@@ -340,14 +334,11 @@ void CppPreprocessor::clearProjectIncludePaths()
     mProjectIncludePathList.clear();
 }
 
-void CppPreprocessor::clearScannedFiles()
+void CppPreprocessor::removeScannedFile(const QString &filename)
 {
-    mScannedFiles.clear();
-}
-
-void CppPreprocessor::clearIncludeList()
-{
-    mIncludesList.clear();
+    mScannedFiles.remove(filename);
+    mIncludesList.remove(filename);
+    mFileDefines.remove(filename);
 }
 
 QString CppPreprocessor::getNextPreprocessor()
diff --git a/RedPandaIDE/parser/cpppreprocessor.h b/RedPandaIDE/parser/cpppreprocessor.h
index 21dd3e36..46ec5e81 100644
--- a/RedPandaIDE/parser/cpppreprocessor.h
+++ b/RedPandaIDE/parser/cpppreprocessor.h
@@ -62,10 +62,10 @@ public:
 
     explicit CppPreprocessor();
     void clear();
-    void clearResult();
+
+    void clearTempResults();
     void getDefineParts(const QString& input, QString &name, QString &args, QString &value);
     void addHardDefineByLine(const QString& line);
-    void reset(); //reset but don't clear generated defines
     void setScanOptions(bool parseSystem, bool parseLocal);
     void preprocess(const QString& fileName, QStringList buffer = QStringList());
 
@@ -75,8 +75,7 @@ public:
     void addProjectIncludePath(const QString& fileName);
     void clearIncludePaths();
     void clearProjectIncludePaths();
-    void clearScannedFiles();
-    void clearIncludeList();
+
     QStringList result() const;
 
     QHash<QString, PFileIncludes> &includesList();
diff --git a/RedPandaIDE/parser/cpptokenizer.cpp b/RedPandaIDE/parser/cpptokenizer.cpp
index 5830c663..39c6262a 100644
--- a/RedPandaIDE/parser/cpptokenizer.cpp
+++ b/RedPandaIDE/parser/cpptokenizer.cpp
@@ -24,7 +24,7 @@ CppTokenizer::CppTokenizer()
 
 }
 
-void CppTokenizer::reset()
+void CppTokenizer::clear()
 {
     mTokenList.clear();
     mBuffer.clear();
@@ -34,7 +34,7 @@ void CppTokenizer::reset()
 
 void CppTokenizer::tokenize(const QStringList &buffer)
 {
-    reset();
+    clear();
 
     mBuffer = buffer;
     if (mBuffer.isEmpty())
diff --git a/RedPandaIDE/parser/cpptokenizer.h b/RedPandaIDE/parser/cpptokenizer.h
index ec8a0426..56080034 100644
--- a/RedPandaIDE/parser/cpptokenizer.h
+++ b/RedPandaIDE/parser/cpptokenizer.h
@@ -31,7 +31,7 @@ public:
     using TokenList = QVector<PToken>;
     explicit CppTokenizer();
 
-    void reset();
+    void clear();
     void tokenize(const QStringList& buffer);
     void dumpTokens(const QString& fileName);
     const TokenList& tokens();
diff --git a/RedPandaIDE/project.cpp b/RedPandaIDE/project.cpp
index baa5913a..1aa2226a 100644
--- a/RedPandaIDE/project.cpp
+++ b/RedPandaIDE/project.cpp
@@ -585,7 +585,7 @@ void Project::resetParserProjectFiles()
     mParser->clearProjectFiles();
     mParser->clearProjectIncludePaths();
     foreach (const PProjectUnit& unit, mUnits) {
-        mParser->addFileToScan(unit->fileName());
+        mParser->addFileToScan(unit->fileName(),true);
     }
     foreach (const QString& s, mOptions.includeDirs) {
         mParser->addProjectIncludePath(s);