diff --git a/lldb/include/lldb/Core/Debugger.h b/lldb/include/lldb/Core/Debugger.h
--- a/lldb/include/lldb/Core/Debugger.h
+++ b/lldb/include/lldb/Core/Debugger.h
@@ -229,7 +229,7 @@
 
   void PrintAsync(const char *s, size_t len, bool is_stdout);
 
-  ConstString GetTopIOHandlerControlSequence(char ch);
+  llvm::StringRef GetTopIOHandlerControlSequence(char ch);
 
   const char *GetIOHandlerCommandPrefix();
 
diff --git a/lldb/include/lldb/Core/IOHandler.h b/lldb/include/lldb/Core/IOHandler.h
--- a/lldb/include/lldb/Core/IOHandler.h
+++ b/lldb/include/lldb/Core/IOHandler.h
@@ -12,7 +12,6 @@
 #include "lldb/Core/ValueObjectList.h"
 #include "lldb/Host/Config.h"
 #include "lldb/Utility/CompletionRequest.h"
-#include "lldb/Utility/ConstString.h"
 #include "lldb/Utility/Flags.h"
 #include "lldb/Utility/Predicate.h"
 #include "lldb/Utility/Stream.h"
@@ -107,7 +106,9 @@
   }
   bool SetPrompt(const char *) = delete;
 
-  virtual ConstString GetControlSequence(char ch) { return ConstString(); }
+  virtual llvm::StringRef GetControlSequence(char ch) {
+    return llvm::StringRef();
+  }
 
   virtual const char *GetCommandPrefix() { return nullptr; }
 
@@ -271,8 +272,8 @@
     return true;
   }
 
-  virtual ConstString IOHandlerGetControlSequence(char ch) {
-    return ConstString();
+  virtual llvm::StringRef IOHandlerGetControlSequence(char ch) {
+    return llvm::StringRef();
   }
 
   virtual const char *IOHandlerGetCommandPrefix() { return nullptr; }
@@ -298,21 +299,24 @@
   IOHandlerDelegateMultiline(const char *end_line,
                              Completion completion = Completion::None)
       : IOHandlerDelegate(completion),
-        m_end_line((end_line && end_line[0]) ? end_line : "") {}
+        m_end_line((end_line && end_line[0]) ? std::string(end_line) + "\n"
+                                             : "\n") {}
 
   ~IOHandlerDelegateMultiline() override = default;
 
-  ConstString IOHandlerGetControlSequence(char ch) override {
+  llvm::StringRef IOHandlerGetControlSequence(char ch) override {
     if (ch == 'd')
-      return ConstString(m_end_line + "\n");
-    return ConstString();
+      return m_end_line;
+    return llvm::StringRef();
   }
 
   bool IOHandlerIsInputComplete(IOHandler &io_handler,
                                 StringList &lines) override {
     // Determine whether the end of input signal has been entered
     const size_t num_lines = lines.GetSize();
-    if (num_lines > 0 && lines[num_lines - 1] == m_end_line) {
+    const llvm::StringRef end_line =
+        llvm::StringRef(m_end_line).drop_back(1); // Drop '\n'
+    if (num_lines > 0 && llvm::StringRef(lines[num_lines - 1]) == end_line) {
       // Remove the terminal line from "lines" so it doesn't appear in the
       // resulting input and return true to indicate we are done getting lines
       lines.PopBack();
@@ -373,7 +377,7 @@
 
   void TerminalSizeChanged() override;
 
-  ConstString GetControlSequence(char ch) override {
+  llvm::StringRef GetControlSequence(char ch) override {
     return m_delegate.IOHandlerGetControlSequence(ch);
   }
 
@@ -522,8 +526,9 @@
             m_stack[num_io_handlers - 2]->GetType() == second_top_type);
   }
 
-  ConstString GetTopIOHandlerControlSequence(char ch) {
-    return ((m_top != nullptr) ? m_top->GetControlSequence(ch) : ConstString());
+  llvm::StringRef GetTopIOHandlerControlSequence(char ch) {
+    return ((m_top != nullptr) ? m_top->GetControlSequence(ch)
+                               : llvm::StringRef());
   }
 
   const char *GetTopIOHandlerCommandPrefix() {
diff --git a/lldb/include/lldb/Expression/REPL.h b/lldb/include/lldb/Expression/REPL.h
--- a/lldb/include/lldb/Expression/REPL.h
+++ b/lldb/include/lldb/Expression/REPL.h
@@ -88,7 +88,7 @@
 
   const char *IOHandlerGetFixIndentationCharacters() override;
 
-  ConstString IOHandlerGetControlSequence(char ch) override;
+  llvm::StringRef IOHandlerGetControlSequence(char ch) override;
 
   const char *IOHandlerGetCommandPrefix() override;
 
diff --git a/lldb/include/lldb/Interpreter/CommandInterpreter.h b/lldb/include/lldb/Interpreter/CommandInterpreter.h
--- a/lldb/include/lldb/Interpreter/CommandInterpreter.h
+++ b/lldb/include/lldb/Interpreter/CommandInterpreter.h
@@ -652,10 +652,11 @@
   void IOHandlerInputComplete(IOHandler &io_handler,
                               std::string &line) override;
 
-  ConstString IOHandlerGetControlSequence(char ch) override {
+  llvm::StringRef IOHandlerGetControlSequence(char ch) override {
+    static constexpr llvm::StringLiteral control_sequence("quit\n");
     if (ch == 'd')
-      return ConstString("quit\n");
-    return ConstString();
+      return control_sequence;
+    return llvm::StringRef();
   }
 
   void GetProcessOutput();
diff --git a/lldb/source/API/SBCommandInterpreter.cpp b/lldb/source/API/SBCommandInterpreter.cpp
--- a/lldb/source/API/SBCommandInterpreter.cpp
+++ b/lldb/source/API/SBCommandInterpreter.cpp
@@ -155,11 +155,12 @@
 const char *SBCommandInterpreter::GetIOHandlerControlSequence(char ch) {
   LLDB_INSTRUMENT_VA(this, ch);
 
-  return (IsValid()
-              ? m_opaque_ptr->GetDebugger()
-                    .GetTopIOHandlerControlSequence(ch)
-                    .GetCString()
-              : nullptr);
+  if (!IsValid())
+    return nullptr;
+
+  return ConstString(
+             m_opaque_ptr->GetDebugger().GetTopIOHandlerControlSequence(ch))
+      .GetCString();
 }
 
 lldb::ReturnStatus
diff --git a/lldb/source/Core/Debugger.cpp b/lldb/source/Core/Debugger.cpp
--- a/lldb/source/Core/Debugger.cpp
+++ b/lldb/source/Core/Debugger.cpp
@@ -1126,7 +1126,7 @@
   }
 }
 
-ConstString Debugger::GetTopIOHandlerControlSequence(char ch) {
+llvm::StringRef Debugger::GetTopIOHandlerControlSequence(char ch) {
   return m_io_handler_stack.GetTopIOHandlerControlSequence(ch);
 }
 
diff --git a/lldb/source/Expression/REPL.cpp b/lldb/source/Expression/REPL.cpp
--- a/lldb/source/Expression/REPL.cpp
+++ b/lldb/source/Expression/REPL.cpp
@@ -117,10 +117,11 @@
   return (m_enable_auto_indent ? GetAutoIndentCharacters() : nullptr);
 }
 
-ConstString REPL::IOHandlerGetControlSequence(char ch) {
+llvm::StringRef REPL::IOHandlerGetControlSequence(char ch) {
+  static constexpr llvm::StringLiteral control_sequence(":quit\n");
   if (ch == 'd')
-    return ConstString(":quit\n");
-  return ConstString();
+    return control_sequence;
+  return llvm::StringRef();
 }
 
 const char *REPL::IOHandlerGetCommandPrefix() { return ":"; }
diff --git a/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h b/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
--- a/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
+++ b/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPythonImpl.h
@@ -434,10 +434,11 @@
 
   ~IOHandlerPythonInterpreter() override = default;
 
-  ConstString GetControlSequence(char ch) override {
+  llvm::StringRef GetControlSequence(char ch) override {
+    static constexpr llvm::StringLiteral control_sequence("quit()\n");
     if (ch == 'd')
-      return ConstString("quit()\n");
-    return ConstString();
+      return control_sequence;
+    return llvm::StringRef();
   }
 
   void Run() override {