Fix destruction ordering on shutdown.

cling is currently tearing down the text input before the Interpreter is destroyed.
Leading to problems with pipes and file handles being close in the text input layer.

Author: marsupial

include/cling/UserInterface/UserInterface.h

@@ -20,17 +20,24 @@ namespace cling {
   ///
   class UserInterface {
   private:
+    class TextInputHolder;
+    std::unique_ptr<TextInputHolder> m_TextInput;
     std::unique_ptr<MetaProcessor> m_MetaProcessor;
 
     ///\brief Prints cling's startup logo
     ///
     void PrintLogo();
   public:
-    UserInterface(Interpreter& interp);
+    UserInterface();
     ~UserInterface();
 
     MetaProcessor* getMetaProcessor() { return m_MetaProcessor.get(); }
 
+    ///\brief Attach this instance to the given Interpreter.
+    /// @param[in] Interp - The interpreter to attach to.
+    ///
+    void attach(Interpreter& Interp);
+
     ///\brief Drives the interactive prompt talking to the user.
     /// @param[in] nologo - whether to show cling's welcome logo or not
     ///

lib/UserInterface/UserInterface.cpp

@@ -46,57 +46,67 @@ namespace {
       return true;
     }
   };
+}
+
+namespace cling {
 
   ///\brief Delays ~TextInput until after ~StreamReader and ~TerminalDisplay
   ///
-  class TextInputHolder {
+  class UserInterface::TextInputHolder {
     textinput::StreamReader* m_Reader;
     textinput::TerminalDisplay* m_Display;
     textinput::TextInput m_Input;
 
+    class HistoryFile {
+      llvm::SmallString<512> Path;
+
+    public:
+      HistoryFile(const char* Env = "CLING_NOHISTORY",
+                  const char* Name = ".cling_history") {
+        if (getenv(Env)) return;
+        // History file is $HOME/.cling_history
+        if (llvm::sys::path::home_directory(Path))
+          llvm::sys::path::append(Path, Name);
+      }
+      const char* c_str() { return Path.empty() ? nullptr : Path.c_str(); }
+    };
+
   public:
-    TextInputHolder(llvm::SmallString<512>& Hist)
+    TextInputHolder(HistoryFile HistFile = HistoryFile())
         : m_Reader(textinput::StreamReader::Create()),
           m_Display(textinput::TerminalDisplay::Create()),
-          m_Input(*m_Reader, *m_Display, Hist.empty() ? 0 : Hist.c_str()) {}
+          m_Input(*m_Reader, *m_Display, HistFile.c_str()) {
+    }
 
     ~TextInputHolder() {
       delete m_Reader;
       delete m_Display;
     }
 
-    textinput::TextInput* operator -> () { return &m_Input; }
+    operator textinput::TextInput& () { return m_Input; }
   };
-}
 
-namespace cling {
-
-  UserInterface::UserInterface(Interpreter& interp) {
-    m_MetaProcessor.reset(new MetaProcessor(interp, cling::outs()));
+  UserInterface::UserInterface() {
     llvm::install_fatal_error_handler(&CompilationException::throwingHandler);
   }
 
-  UserInterface::~UserInterface() {}
+  UserInterface::~UserInterface() { llvm::remove_fatal_error_handler(); }
+
+  void UserInterface::attach(Interpreter& Interp) {
+    m_MetaProcessor.reset(new MetaProcessor(Interp, cling::outs()));
+  }
 
   void UserInterface::runInteractively(bool nologo /* = false */) {
-    if (!nologo) {
+    assert(m_MetaProcessor.get() && "Not attached to an Interpreter.");
+    if (!nologo)
       PrintLogo();
-    }
-
-    llvm::SmallString<512> histfilePath;
-    if (!getenv("CLING_NOHISTORY")) {
-      // History file is $HOME/.cling_history
-      if (llvm::sys::path::home_directory(histfilePath))
-        llvm::sys::path::append(histfilePath, ".cling_history");
-    }
 
-    TextInputHolder TI(histfilePath);
+    m_TextInput.reset(new TextInputHolder);
+    textinput::TextInput& TI = *m_TextInput;
 
     // Inform text input about the code complete consumer
     // TextInput owns the TabCompletion.
-    UITabCompletion* Completion =
-                      new UITabCompletion(m_MetaProcessor->getInterpreter());
-    TI->SetCompletion(Completion);
+    TI.SetCompletion(new UITabCompletion(m_MetaProcessor->getInterpreter()));
 
     bool Done = false;
     std::string Line;
@@ -107,9 +117,9 @@ namespace cling {
         m_MetaProcessor->getOuts().flush();
         {
           MetaProcessor::MaybeRedirectOutputRAII RAII(*m_MetaProcessor);
-          TI->SetPrompt(Prompt.c_str());
-          Done = TI->ReadInput() == textinput::TextInput::kRREOF;
-          TI->TakeInput(Line);
+          TI.SetPrompt(Prompt.c_str());
+          Done = TI.ReadInput() == textinput::TextInput::kRREOF;
+          TI.TakeInput(Line);
           if (Done && Line.empty())
             break;
         }

tools/driver/cling.cpp

@@ -53,6 +53,9 @@ static int checkDiagErrors(clang::CompilerInstance* CI, unsigned* OutErrs = 0) {
 
 
 int main( int argc, char **argv ) {
+  // Force the UserInterface to be destroyed last, so any file manipulation,
+  // pipes, or dups are active for the entire process.
+  cling::UserInterface Ui;
 
   llvm::llvm_shutdown_obj shutdownTrigger;
 
@@ -105,7 +108,7 @@ int main( int argc, char **argv ) {
   for (const std::string& Lib : Opts.LibsToLoad)
     Interp.loadFile(Lib);
 
-  cling::UserInterface Ui(Interp);
+  Ui.attach(Interp);
   // If we are not interactive we're supposed to parse files
   if (!Opts.IsInteractive()) {
     for (const std::string &Input : Opts.Inputs) {