Revert "Revert "Add the ability to write target stop-hooks using the ScriptInterpreter.""

This reverts commit f775fe5.

I fixed a return type error in the original patch that was causing a test failure.
Also added a REQUIRES: python to the shell test so we'll skip this for
people who build lldb w/o Python.
Also added another test for the error printing.

Author: jimingham

lldb/bindings/python/python-swigsafecast.swig

@@ -152,3 +152,10 @@ SBTypeToSWIGWrapper (lldb::SBSymbolContext* sym_ctx_sb)
 {
     return SWIG_NewPointerObj((void *) sym_ctx_sb, SWIGTYPE_p_lldb__SBSymbolContext, 0);
 }
+
+template <>
+PyObject*
+SBTypeToSWIGWrapper (lldb::SBStream* stream_sb)
+{
+    return SWIG_NewPointerObj((void *) stream_sb, SWIGTYPE_p_lldb__SBStream, 0);
+}

lldb/bindings/python/python-wrapper.swig

@@ -468,6 +468,127 @@ LLDBSwigPythonCallBreakpointResolver
     return ret_val;
 }
 
+SWIGEXPORT void *
+LLDBSwigPythonCreateScriptedStopHook
+(
+    lldb::TargetSP target_sp,
+    const char *python_class_name,
+    const char *session_dictionary_name,
+    lldb_private::StructuredDataImpl *args_impl,
+    Status &error
+)
+{
+    if (python_class_name == NULL || python_class_name[0] == '\0') {
+        error.SetErrorString("Empty class name.");
+        Py_RETURN_NONE;
+    }
+    if (!session_dictionary_name) {
+      error.SetErrorString("No session dictionary");
+      Py_RETURN_NONE;
+    }
+    
+    PyErr_Cleaner py_err_cleaner(true);
+
+    auto dict = 
+        PythonModule::MainModule().ResolveName<PythonDictionary>(
+            session_dictionary_name);
+    auto pfunc = 
+        PythonObject::ResolveNameWithDictionary<PythonCallable>(
+            python_class_name, dict);
+
+    if (!pfunc.IsAllocated()) {
+        error.SetErrorStringWithFormat("Could not find class: %s.", 
+                                       python_class_name);
+        return nullptr;
+    }
+
+    lldb::SBTarget *target_val 
+        = new lldb::SBTarget(target_sp);
+
+    PythonObject target_arg(PyRefType::Owned, SBTypeToSWIGWrapper(target_val));
+
+    lldb::SBStructuredData *args_value = new lldb::SBStructuredData(args_impl);
+    PythonObject args_arg(PyRefType::Owned, SBTypeToSWIGWrapper(args_value));
+
+    PythonObject result = pfunc(target_arg, args_arg, dict);
+
+    if (result.IsAllocated())
+    {
+        // Check that the handle_stop callback is defined:
+        auto callback_func = result.ResolveName<PythonCallable>("handle_stop");
+        if (callback_func.IsAllocated()) {
+          if (auto args_info = callback_func.GetArgInfo()) {
+            size_t num_args = (*args_info).max_positional_args; 
+            if (num_args != 2) {
+              error.SetErrorStringWithFormat("Wrong number of args for "
+              "handle_stop callback, should be 2 (excluding self), got: %d", 
+              num_args);
+              Py_RETURN_NONE;
+            } else
+              return result.release();
+          } else {
+            error.SetErrorString("Couldn't get num arguments for handle_stop "
+                                 "callback.");
+            Py_RETURN_NONE;
+          }
+          return result.release();
+        }
+        else {
+          error.SetErrorStringWithFormat("Class \"%s\" is missing the required "
+                                         "handle_stop callback.",
+                                         python_class_name);
+          result.release();
+        }
+    }
+    Py_RETURN_NONE;
+}
+
+SWIGEXPORT bool
+LLDBSwigPythonStopHookCallHandleStop
+(
+    void *implementor,
+    lldb::ExecutionContextRefSP exc_ctx_sp,
+    lldb::StreamSP stream
+)
+{
+    // handle_stop will return a bool with the meaning "should_stop"...
+    // If you return nothing we'll assume we are going to stop.
+    // Also any errors should return true, since we should stop on error.
+
+    PyErr_Cleaner py_err_cleaner(false);
+    PythonObject self(PyRefType::Borrowed, static_cast<PyObject*>(implementor));
+    auto pfunc = self.ResolveName<PythonCallable>("handle_stop");
+
+    if (!pfunc.IsAllocated())
+        return true;
+
+    PythonObject result;
+    lldb::SBExecutionContext sb_exc_ctx(exc_ctx_sp);
+    PythonObject exc_ctx_arg(PyRefType::Owned, SBTypeToSWIGWrapper(sb_exc_ctx));
+    lldb::SBStream sb_stream;
+    PythonObject sb_stream_arg(PyRefType::Owned, 
+                               SBTypeToSWIGWrapper(sb_stream));
+    result = pfunc(exc_ctx_arg, sb_stream_arg);
+
+    if (PyErr_Occurred())
+    {
+        stream->PutCString("Python error occurred handling stop-hook.");
+        PyErr_Print();
+        PyErr_Clear();
+        return true;
+    }
+    
+    // Now add the result to the output stream.  SBStream only
+    // makes an internally help StreamString which I can't interpose, so I 
+    // have to copy it over here.
+    stream->PutCString(sb_stream.GetData());
+    
+    if (result.get() == Py_False)
+      return false;
+    else
+      return true;
+}
+
 // wrapper that calls an optional instance member of an object taking no arguments
 static PyObject*
 LLDBSwigPython_CallOptionalMember

lldb/docs/use/python-reference.rst

@@ -819,3 +819,49 @@ When the program is stopped at the beginning of the 'read' function in libc, we
       frame #0: 0x00007fff06013ca0 libsystem_kernel.dylib`read
   (lldb) frame variable
   (int) fd = 3
+
+ Writing Target Stop-Hooks in Python:
+ ------------------------------------
+
+ Stop hooks fire whenever the process stops just before control is returned to the
+ user.  Stop hooks can either be a set of lldb command-line commands, or can
+ be implemented by a suitably defined Python class.  The Python based stop-hooks
+ can also be passed as set of -key -value pairs when they are added, and those
+ will get packaged up into a SBStructuredData Dictionary and passed to the
+ constructor of the Python object managing the stop hook.  This allows for
+ parametrization of the stop hooks.
+
+ To add a Python-based stop hook, first define a class with the following methods:
+
++--------------------+---------------------------------------+------------------------------------------------------------------------------------------------------------------+
+| Name               | Arguments                             | Description                                                                                                      |
++--------------------+---------------------------------------+------------------------------------------------------------------------------------------------------------------+
+| **__init__**       | **target: lldb.SBTarget**             | This is the constructor for the new stop-hook.                                                                   |
+|                    | **extra_args: lldb.SBStructuredData** |                                                                                                                  |
+|                    |                                       |                                                                                                                  |
+|                    |                                       | **target** is the SBTarget to which the stop hook is added.                                                      |
+|                    |                                       |                                                                                                                  |
+|                    |                                       | **extra_args** is an SBStructuredData object that the user can pass in when creating instances of this           |
+|                    |                                       | breakpoint.  It is not required, but allows for reuse of stop-hook classes.                                      |
++--------------------+---------------------------------------+------------------------------------------------------------------------------------------------------------------+
+| **handle_stop**    | **exe_ctx: lldb.SBExecutionContext**  | This is the called when the target stops.                                                                        |
+|                    | **stream: lldb.SBStream**             |                                                                                                                  |
+|                    |                                       | **exe_ctx** argument will be filled with the current stop point for which the stop hook is                       |
+|                    |                                       | being evaluated.                                                                                                 |
+|                    |                                       |                                                                                                                  |
+|                    |                                       | **stream** an lldb.SBStream, anything written to this stream will be written to the debugger console.            |
+|                    |                                       |                                                                                                                  |
+|                    |                                       | The return value is a "Should Stop" vote from this thread.  If the method returns either True or no return       |
+|                    |                                       | this thread votes to stop.  If it returns False, then the thread votes to continue after all the stop-hooks      |
+|                    |                                       | are evaluated.                                                                                                   |
+|                    |                                       | Note, the --auto-continue flag to 'target stop-hook add' overrides a True return value from the method.          |
++--------------------+---------------------------------------+------------------------------------------------------------------------------------------------------------------+
+
+To use this class in lldb, run the command:
+
+::
+
+   (lldb) command script import MyModule.py
+   (lldb) target stop-hook add -P MyModule.MyStopHook -k first -v 1 -k second -v 2
+
+where MyModule.py is the file containing the class definition MyStopHook.

lldb/include/lldb/Interpreter/ScriptInterpreter.h

@@ -298,6 +298,23 @@ class ScriptInterpreter : public PluginInterface {
     return lldb::eSearchDepthModule;
   }
 
+  virtual StructuredData::GenericSP
+  CreateScriptedStopHook(lldb::TargetSP target_sp, const char *class_name,
+                         StructuredDataImpl *args_data, Status &error) {
+    error.SetErrorString("Creating scripted stop-hooks with the current "
+                         "script interpreter is not supported.");
+    return StructuredData::GenericSP();
+  }
+
+  // This dispatches to the handle_stop method of the stop-hook class.  It
+  // returns a "should_stop" bool.
+  virtual bool
+  ScriptedStopHookHandleStop(StructuredData::GenericSP implementor_sp,
+                             ExecutionContext &exc_ctx,
+                             lldb::StreamSP stream_sp) {
+    return true;
+  }
+
   virtual StructuredData::ObjectSP
   LoadPluginModule(const FileSpec &file_spec, lldb_private::Status &error) {
     return StructuredData::ObjectSP();

lldb/include/lldb/Symbol/SymbolContext.h

@@ -340,7 +340,7 @@ class SymbolContextSpecifier {
 
   void Clear();
 
-  bool SymbolContextMatches(SymbolContext &sc);
+  bool SymbolContextMatches(const SymbolContext &sc);
 
   bool AddressMatches(lldb::addr_t addr);
 

lldb/include/lldb/Target/Target.h

@@ -28,6 +28,7 @@
 #include "lldb/Target/ExecutionContextScope.h"
 #include "lldb/Target/PathMappingList.h"
 #include "lldb/Target/SectionLoadHistory.h"
+#include "lldb/Target/ThreadSpec.h"
 #include "lldb/Utility/ArchSpec.h"
 #include "lldb/Utility/Broadcaster.h"
 #include "lldb/Utility/LLDBAssert.h"
@@ -508,6 +509,8 @@ class Target : public std::enable_shared_from_this<Target>,
 
   static void SetDefaultArchitecture(const ArchSpec &arch);
 
+  bool IsDummyTarget() const { return m_is_dummy_target; }
+
   /// Find a binary on the system and return its Module,
   /// or return an existing Module that is already in the Target.
   ///
@@ -1139,23 +1142,27 @@ class Target : public std::enable_shared_from_this<Target>,
   class StopHook : public UserID {
   public:
     StopHook(const StopHook &rhs);
+    virtual ~StopHook() = default;
 
-    ~StopHook();
-
-    StringList *GetCommandPointer() { return &m_commands; }
-
-    const StringList &GetCommands() { return m_commands; }
+    enum class StopHookKind  : uint32_t { CommandBased = 0, ScriptBased };
 
     lldb::TargetSP &GetTarget() { return m_target_sp; }
 
-    void SetCommands(StringList &in_commands) { m_commands = in_commands; }
-
     // Set the specifier.  The stop hook will own the specifier, and is
     // responsible for deleting it when we're done.
     void SetSpecifier(SymbolContextSpecifier *specifier);
 
     SymbolContextSpecifier *GetSpecifier() { return m_specifier_sp.get(); }
 
+    bool ExecutionContextPasses(const ExecutionContext &exe_ctx);
+
+    // Called on stop, this gets passed the ExecutionContext for each "stop
+    // with a reason" thread.  It should add to the stream whatever text it
+    // wants to show the user, and return False to indicate it wants the target
+    // not to stop.
+    virtual bool HandleStop(ExecutionContext &exe_ctx,
+                            lldb::StreamSP output) = 0;
+
     // Set the Thread Specifier.  The stop hook will own the thread specifier,
     // and is responsible for deleting it when we're done.
     void SetThreadSpecifier(ThreadSpec *specifier);
@@ -1173,26 +1180,79 @@ class Target : public std::enable_shared_from_this<Target>,
     bool GetAutoContinue() const { return m_auto_continue; }
 
     void GetDescription(Stream *s, lldb::DescriptionLevel level) const;
+    virtual void GetSubclassDescription(Stream *s,
+                                        lldb::DescriptionLevel level) const = 0;
 
-  private:
+  protected:
     lldb::TargetSP m_target_sp;
-    StringList m_commands;
     lldb::SymbolContextSpecifierSP m_specifier_sp;
     std::unique_ptr<ThreadSpec> m_thread_spec_up;
     bool m_active = true;
     bool m_auto_continue = false;
 
+    StopHook(lldb::TargetSP target_sp, lldb::user_id_t uid);
+  };
+
+  class StopHookCommandLine : public StopHook {
+  public:
+    virtual ~StopHookCommandLine() = default;
+
+    StringList &GetCommands() { return m_commands; }
+    void SetActionFromString(const std::string &strings);
+    void SetActionFromStrings(const std::vector<std::string> &strings);
+
+    bool HandleStop(ExecutionContext &exc_ctx,
+                    lldb::StreamSP output_sp) override;
+    void GetSubclassDescription(Stream *s,
+                                lldb::DescriptionLevel level) const override;
+
+  private:
+    StringList m_commands;
     // Use CreateStopHook to make a new empty stop hook. The GetCommandPointer
     // and fill it with commands, and SetSpecifier to set the specifier shared
     // pointer (can be null, that will match anything.)
-    StopHook(lldb::TargetSP target_sp, lldb::user_id_t uid);
+    StopHookCommandLine(lldb::TargetSP target_sp, lldb::user_id_t uid)
+        : StopHook(target_sp, uid) {}
+    friend class Target;
+  };
+
+  class StopHookScripted : public StopHook {
+  public:
+    virtual ~StopHookScripted() = default;
+    bool HandleStop(ExecutionContext &exc_ctx, lldb::StreamSP output) override;
+
+    Status SetScriptCallback(std::string class_name,
+                             StructuredData::ObjectSP extra_args_sp);
+
+    void GetSubclassDescription(Stream *s,
+                                lldb::DescriptionLevel level) const override;
+
+  private:
+    std::string m_class_name;
+    /// This holds the dictionary of keys & values that can be used to
+    /// parametrize any given callback's behavior.
+    StructuredDataImpl *m_extra_args; // We own this structured data,
+                                      // but the SD itself manages the UP.
+    /// This holds the python callback object.
+    StructuredData::GenericSP m_implementation_sp; 
+
+    /// Use CreateStopHook to make a new empty stop hook. The GetCommandPointer
+    /// and fill it with commands, and SetSpecifier to set the specifier shared
+    /// pointer (can be null, that will match anything.)
+    StopHookScripted(lldb::TargetSP target_sp, lldb::user_id_t uid)
+        : StopHook(target_sp, uid) {}
     friend class Target;
   };
+
   typedef std::shared_ptr<StopHook> StopHookSP;
 
-  // Add an empty stop hook to the Target's stop hook list, and returns a
-  // shared pointer to it in new_hook. Returns the id of the new hook.
-  StopHookSP CreateStopHook();
+  /// Add an empty stop hook to the Target's stop hook list, and returns a
+  /// shared pointer to it in new_hook. Returns the id of the new hook.
+  StopHookSP CreateStopHook(StopHook::StopHookKind kind);
+
+  /// If you tried to create a stop hook, and that failed, call this to
+  /// remove the stop hook, as it will also reset the stop hook counter.
+  void UndoCreateStopHook(lldb::user_id_t uid);
 
   void RunStopHooks();