Add more handy interface that takes a number of transactions to be rolled back.

include/cling/Interpreter/Interpreter.h

@@ -249,9 +249,6 @@ namespace cling {
     void ignoreFakeDiagnostics() const;
 
   public:
-
-    void unload();
-
     Interpreter(int argc, const char* const *argv, const char* llvmdir = 0);
     virtual ~Interpreter();
 
@@ -481,6 +478,13 @@ namespace cling {
     CompilationResult loadFile(const std::string& filename,
                                bool allowSharedLib = true);
 
+    ///\brief Unloads (forgets) given number of transactions.
+    ///
+    ///\param[in] numberOfTransactions - how many transactions to revert 
+    ///                                  starting from the last.
+    ///
+    void unload(unsigned numberOfTransactions);
+
     bool isPrintingAST() const { return m_PrintAST; }
     void enablePrintAST(bool print = true) { m_PrintAST = print; }
 

lib/Interpreter/IncrementalParser.cpp

@@ -615,6 +615,17 @@ namespace cling {
     return IncrementalParser::kSuccess;
   }
 
+  void IncrementalParser::unloadLastNTransactions(unsigned N) {
+    assert(N <= m_Transactions.size() && "Unloading more than ever seen.");
+    
+    while(true) {
+      unloadTransaction(m_Transactions.back());
+      m_Transactions.pop_back();
+      if (!N--)
+        break;
+    } 
+  }
+  
   void IncrementalParser::unloadTransaction(Transaction* T) {
     if (!T)
       T = getLastTransaction();

lib/Interpreter/IncrementalParser.h

@@ -191,7 +191,18 @@ namespace cling {
     ///
     Transaction* Parse(llvm::StringRef input, const CompilationOptions& Opts);
 
+    ///\brief Unloads last N transactions.
+    ///
+    ///\param[in] N - how many starting from the last seen.
+    ///
+    void unloadLastNTransactions(unsigned N);
+
+    ///\brief Unloads a given transaction.
+    ///
+    ///\param[in] T - The transaction to unload.
+    ///
     void unloadTransaction(Transaction* T);
+
     void printTransactionStructure() const;
 
     ///\brief Adds a UsedAttr to all decls in the transaction.

lib/Interpreter/Interpreter.cpp

@@ -148,10 +148,6 @@ namespace cling {
     return m_IncrParser->getCodeGenerator();
   }
 
-  void Interpreter::unload() {
-    m_IncrParser->unloadTransaction(0);
-  }
-
   Interpreter::Interpreter(int argc, const char* const *argv,
                            const char* llvmdir /*= 0*/) :
     m_UniqueCounter(0), m_PrintAST(false), m_PrintIR(false), 
@@ -772,6 +768,10 @@ namespace cling {
     return res;
   }
 
+  void Interpreter::unload(unsigned numberOfTransactions) {
+    m_IncrParser->unloadLastNTransactions(numberOfTransactions);
+  }
+
   void Interpreter::installLazyFunctionCreator(void* (*fp)(const std::string&)) {
     m_ExecutionContext->installLazyFunctionCreator(fp);
   }