[LLDB] Implement interactive command interruption

The core of this change is the new CommandInterpreter::m_command_state, which
models the state transitions for interactive commands, including an
"interrupted" state transition.

In general, command interruption requires cooperation from the code executing
the command, which needs to poll for interruption requests through
CommandInterpreter::WasInterrupted().

CommandInterpreter::PrintCommandOutput() implements an optionally
interruptible printing of the command output, which for large outputs was
likely the longest blocking part.  (ex. target modules dump symtab on a
complex binary could take 10+ minutes)

patch by lemo

Differential Revision: https://reviews.llvm.org/D37923

llvm-svn: 313904

lldb/include/lldb/API/SBCommandInterpreter.h

@@ -165,6 +165,8 @@ public:
                        int match_start_point, int max_return_elements,
                        lldb::SBStringList &matches);
 
+  bool WasInterrupted() const;
+
   // Catch commands before they execute by registering a callback that will
   // get called when the command gets executed. This allows GUI or command
   // line interfaces to intercept a command and stop it from happening

lldb/include/lldb/Core/IOHandler.h

@@ -195,7 +195,7 @@ public:
   enum class Completion { None, LLDBCommand, Expression };
 
   IOHandlerDelegate(Completion completion = Completion::None)
-      : m_completion(completion), m_io_handler_done(false) {}
+      : m_completion(completion) {}
 
   virtual ~IOHandlerDelegate() = default;
 
@@ -296,7 +296,6 @@ public:
 
 protected:
   Completion m_completion; // Support for common builtin completions
-  bool m_io_handler_done;
 };
 
 //----------------------------------------------------------------------

lldb/include/lldb/Interpreter/CommandInterpreter.h

@@ -242,6 +242,8 @@ public:
                      bool repeat_on_empty_command = true,
                      bool no_context_switching = false);
 
+  bool WasInterrupted() const;
+
   //------------------------------------------------------------------
   /// Execute a list of commands in sequence.
   ///
@@ -522,6 +524,24 @@ private:
                               StringList &commands_help,
                               CommandObject::CommandMap &command_map);
 
+  // An interruptible wrapper around the stream output
+  void PrintCommandOutput(Stream &stream, llvm::StringRef str,
+                          bool interruptible);
+
+  // A very simple state machine which models the command handling transitions
+  enum class CommandHandlingState {
+    eIdle,
+    eInProgress,
+    eInterrupted,
+  };
+
+  std::atomic<CommandHandlingState> m_command_state{
+      CommandHandlingState::eIdle};
+
+  void StartHandlingCommand();
+  void FinishHandlingCommand();
+  bool InterruptCommand();
+
   Debugger &m_debugger; // The debugger session that this interpreter is
                         // associated with
   ExecutionContextRef m_exe_ctx_ref; // The current execution context to use

lldb/scripts/interface/SBCommandInterpreter.i

@@ -213,6 +213,8 @@ public:
     bool
     IsActive ();
 
+    bool
+    WasInterrupted () const;
 };
 
 } // namespace lldb

lldb/source/API/SBCommandInterpreter.cpp

@@ -161,6 +161,10 @@ bool SBCommandInterpreter::IsActive() {
   return (IsValid() ? m_opaque_ptr->IsActive() : false);
 }
 
+bool SBCommandInterpreter::WasInterrupted() const {
+  return (IsValid() ? m_opaque_ptr->WasInterrupted() : false);
+}
+
 const char *SBCommandInterpreter::GetIOHandlerControlSequence(char ch) {
   return (IsValid()
               ? m_opaque_ptr->GetDebugger()

lldb/source/Commands/CommandObjectTarget.cpp

@@ -2053,6 +2053,8 @@ protected:
               result.GetOutputStream().EOL();
               result.GetOutputStream().EOL();
             }
+            if (m_interpreter.WasInterrupted())
+              break;
             num_dumped++;
             DumpModuleSymtab(
                 m_interpreter, result.GetOutputStream(),
@@ -2081,6 +2083,8 @@ protected:
                   result.GetOutputStream().EOL();
                   result.GetOutputStream().EOL();
                 }
+                if (m_interpreter.WasInterrupted())
+                  break;
                 num_dumped++;
                 DumpModuleSymtab(m_interpreter, result.GetOutputStream(),
                                  module, m_options.m_sort_order);
@@ -2146,6 +2150,8 @@ protected:
                                           " modules.\n",
                                           (uint64_t)num_modules);
           for (size_t image_idx = 0; image_idx < num_modules; ++image_idx) {
+            if (m_interpreter.WasInterrupted())
+              break;
             num_dumped++;
             DumpModuleSections(
                 m_interpreter, result.GetOutputStream(),
@@ -2167,6 +2173,8 @@ protected:
               FindModulesByName(target, arg_cstr, module_list, true);
           if (num_matches > 0) {
             for (size_t i = 0; i < num_matches; ++i) {
+              if (m_interpreter.WasInterrupted())
+                break;
               Module *module = module_list.GetModulePointerAtIndex(i);
               if (module) {
                 num_dumped++;
@@ -2239,6 +2247,8 @@ protected:
                                           " modules.\n",
                                           (uint64_t)num_modules);
           for (uint32_t image_idx = 0; image_idx < num_modules; ++image_idx) {
+            if (m_interpreter.WasInterrupted())
+              break;
             if (DumpModuleSymbolVendor(
                     result.GetOutputStream(),
                     target_modules.GetModulePointerAtIndexUnlocked(image_idx)))
@@ -2260,6 +2270,8 @@ protected:
               FindModulesByName(target, arg_cstr, module_list, true);
           if (num_matches > 0) {
             for (size_t i = 0; i < num_matches; ++i) {
+              if (m_interpreter.WasInterrupted())
+                break;
               Module *module = module_list.GetModulePointerAtIndex(i);
               if (module) {
                 if (DumpModuleSymbolVendor(result.GetOutputStream(), module))
@@ -2327,6 +2339,8 @@ protected:
         if (num_modules > 0) {
           uint32_t num_dumped = 0;
           for (uint32_t i = 0; i < num_modules; ++i) {
+            if (m_interpreter.WasInterrupted())
+              break;
             if (DumpCompileUnitLineTable(
                     m_interpreter, result.GetOutputStream(),
                     target_modules.GetModulePointerAtIndexUnlocked(i),

lldb/source/Interpreter/CommandInterpreter.cpp

@@ -546,7 +546,7 @@ void CommandInterpreter::LoadCommandDictionary() {
       char buffer[1024];
       int num_printed =
           snprintf(buffer, 1024, "%s %s", break_regexes[i][1], "-o");
-      assert(num_printed < 1024);
+      lldbassert(num_printed < 1024);
       UNUSED_IF_ASSERT_DISABLED(num_printed);
       success =
           tbreak_regex_cmd_ap->AddRegexCommand(break_regexes[i][0], buffer);
@@ -891,8 +891,8 @@ bool CommandInterpreter::AddCommand(llvm::StringRef name,
                                     const lldb::CommandObjectSP &cmd_sp,
                                     bool can_replace) {
   if (cmd_sp.get())
-    assert((this == &cmd_sp->GetCommandInterpreter()) &&
-           "tried to add a CommandObject from a different interpreter");
+    lldbassert((this == &cmd_sp->GetCommandInterpreter()) &&
+               "tried to add a CommandObject from a different interpreter");
 
   if (name.empty())
     return false;
@@ -913,8 +913,8 @@ bool CommandInterpreter::AddUserCommand(llvm::StringRef name,
                                         const lldb::CommandObjectSP &cmd_sp,
                                         bool can_replace) {
   if (cmd_sp.get())
-    assert((this == &cmd_sp->GetCommandInterpreter()) &&
-           "tried to add a CommandObject from a different interpreter");
+    lldbassert((this == &cmd_sp->GetCommandInterpreter()) &&
+               "tried to add a CommandObject from a different interpreter");
 
   if (!name.empty()) {
     // do not allow replacement of internal commands
@@ -1062,8 +1062,8 @@ CommandInterpreter::AddAlias(llvm::StringRef alias_name,
                              lldb::CommandObjectSP &command_obj_sp,
                              llvm::StringRef args_string) {
   if (command_obj_sp.get())
-    assert((this == &command_obj_sp->GetCommandInterpreter()) &&
-           "tried to add a CommandObject from a different interpreter");
+    lldbassert((this == &command_obj_sp->GetCommandInterpreter()) &&
+               "tried to add a CommandObject from a different interpreter");
 
   std::unique_ptr<CommandAlias> command_alias_up(
       new CommandAlias(*this, command_obj_sp, args_string, alias_name));
@@ -1839,7 +1839,7 @@ int CommandInterpreter::HandleCompletion(
   matches.Clear();
 
   // Only max_return_elements == -1 is supported at present:
-  assert(max_return_elements == -1);
+  lldbassert(max_return_elements == -1);
   bool word_complete;
   num_command_matches = HandleCompletionMatches(
       parsed_line, cursor_index, cursor_char_position, match_start_point,
@@ -2677,6 +2677,57 @@ size_t CommandInterpreter::GetProcessOutput() {
   return total_bytes;
 }
 
+void CommandInterpreter::StartHandlingCommand() {
+  auto prev_state = m_command_state.exchange(CommandHandlingState::eInProgress);
+  lldbassert(prev_state == CommandHandlingState::eIdle);
+}
+
+void CommandInterpreter::FinishHandlingCommand() {
+  auto prev_state = m_command_state.exchange(CommandHandlingState::eIdle);
+  lldbassert(prev_state != CommandHandlingState::eIdle);
+}
+
+bool CommandInterpreter::InterruptCommand() {
+  auto in_progress = CommandHandlingState::eInProgress;
+  return m_command_state.compare_exchange_strong(
+      in_progress, CommandHandlingState::eInterrupted);
+}
+
+bool CommandInterpreter::WasInterrupted() const {
+  return m_command_state == CommandHandlingState::eInterrupted;
+}
+
+void CommandInterpreter::PrintCommandOutput(Stream &stream, llvm::StringRef str,
+                                            bool interruptible) {
+  if (str.empty())
+    return;
+
+  if (interruptible) {
+    // Split the output into lines and poll for interrupt requests
+    const char *data = str.data();
+    size_t size = str.size();
+    while (size > 0 && !WasInterrupted()) {
+      size_t chunk_size = 0;
+      for (; chunk_size < size; ++chunk_size) {
+        lldbassert(data[chunk_size] != '\0');
+        if (data[chunk_size] == '\n') {
+          ++chunk_size;
+          break;
+        }
+      }
+      chunk_size = stream.Write(data, chunk_size);
+      lldbassert(size >= chunk_size);
+      data += chunk_size;
+      size -= chunk_size;
+    }
+    if (size > 0) {
+      stream.Printf("\n... Interrupted.\n");
+    }
+  } else {
+    stream.PutCString(str);
+  }
+}
+
 void CommandInterpreter::IOHandlerInputComplete(IOHandler &io_handler,
                                                 std::string &line) {
   const bool is_interactive = io_handler.GetIsInteractive();
@@ -2700,6 +2751,8 @@ void CommandInterpreter::IOHandlerInputComplete(IOHandler &io_handler,
                                                line.c_str());
   }
 
+  StartHandlingCommand();
+
   lldb_private::CommandReturnObject result;
   HandleCommand(line.c_str(), eLazyBoolCalculate, result);
 
@@ -2710,18 +2763,20 @@ void CommandInterpreter::IOHandlerInputComplete(IOHandler &io_handler,
 
     if (!result.GetImmediateOutputStream()) {
       llvm::StringRef output = result.GetOutputData();
-      if (!output.empty())
-        io_handler.GetOutputStreamFile()->PutCString(output);
+      PrintCommandOutput(*io_handler.GetOutputStreamFile(), output,
+                         is_interactive);
     }
 
     // Now emit the command error text from the command we just executed
     if (!result.GetImmediateErrorStream()) {
       llvm::StringRef error = result.GetErrorData();
-      if (!error.empty())
-        io_handler.GetErrorStreamFile()->PutCString(error);
+      PrintCommandOutput(*io_handler.GetErrorStreamFile(), error,
+                         is_interactive);
     }
   }
 
+  FinishHandlingCommand();
+
   switch (result.GetStatus()) {
   case eReturnStatusInvalid:
   case eReturnStatusSuccessFinishNoResult:
@@ -2777,6 +2832,9 @@ bool CommandInterpreter::IOHandlerInterrupt(IOHandler &io_handler) {
   ExecutionContext exe_ctx(GetExecutionContext());
   Process *process = exe_ctx.GetProcessPtr();
 
+  if (InterruptCommand())
+    return true;
+
   if (process) {
     StateType state = process->GetState();
     if (StateIsRunningState(state)) {
@@ -2998,7 +3056,7 @@ CommandInterpreter::ResolveCommandImpl(std::string &command_line,
         result.AppendRawError(error_msg.GetString());
       } else {
         // We didn't have only one match, otherwise we wouldn't get here.
-        assert(num_matches == 0);
+        lldbassert(num_matches == 0);
         result.AppendErrorWithFormat("'%s' is not a valid command.\n",
                                      next_word.c_str());
       }