Implementing the notion of externally-acquirable ScriptInterpreter lock

With this notion, if parties outside the ScriptInterpreter itself need to acquire a lock on script APIs, they can do so by a pattern like this:

{
auto lock = interpeter->AcquireInterpreterLock();
// do whatever you need to do...
} // lock will automatically be released here

This might be useful for classes that use the Python convenience objects (e.g. PythonDictionary) to ensure they keep the underlying interpreter in a safe and controlled condition while they call through the C API functions
Of course, the ScriptInterpreter still manages its internal locking correctly when necessary :-)

llvm-svn: 178189

lldb/include/lldb/Interpreter/ScriptInterpreter.h

@@ -61,6 +61,22 @@ public:
 protected:
     void* m_object;
 };
+    
+class ScriptInterpreterLocker
+{
+public:
+    
+    ScriptInterpreterLocker ()
+    {
+    }
+    
+    virtual ~ScriptInterpreterLocker ()
+    {
+    }
+private:
+    DISALLOW_COPY_AND_ASSIGN (ScriptInterpreterLocker);
+};
+
 
 class ScriptInterpreter
 {
@@ -409,6 +425,9 @@ public:
         return lldb::ScriptInterpreterObjectSP(new ScriptInterpreterObject(object));
     }
     
+    virtual std::auto_ptr<ScriptInterpreterLocker>
+    AcquireInterpreterLock ();
+    
     const char *
     GetScriptInterpreterPtyName ();
 

lldb/include/lldb/Interpreter/ScriptInterpreterPython.h

@@ -181,6 +181,9 @@ public:
     virtual lldb::ScriptInterpreterObjectSP
     MakeScriptObject (void* object);
     
+    virtual std::auto_ptr<ScriptInterpreterLocker>
+    AcquireInterpreterLock ();
+    
     void
     CollectDataForBreakpointCommandCallback (BreakpointOptions *bp_options,
                                              CommandReturnObject &result);
@@ -271,7 +274,7 @@ private:
             DISALLOW_COPY_AND_ASSIGN (ScriptInterpreterPythonObject);
     };
     
-	class Locker
+	class Locker : public ScriptInterpreterLocker
 	{
 	public:
         

lldb/include/lldb/lldb-forward.h

@@ -178,6 +178,7 @@ class   RegisterValue;
 class   RegularExpression;
 class   Scalar;
 class   ScriptInterpreter;
+class   ScriptInterpreterLocker;
 class   ScriptInterpreterObject;
 #ifndef LLDB_DISABLE_PYTHON
 class   ScriptInterpreterPython;

lldb/source/Interpreter/ScriptInterpreter.cpp

@@ -81,6 +81,12 @@ ScriptInterpreter::LanguageToString (lldb::ScriptLanguage language)
     return return_value;
 }
 
+std::auto_ptr<ScriptInterpreterLocker>
+ScriptInterpreter::AcquireInterpreterLock ()
+{
+    return std::auto_ptr<ScriptInterpreterLocker>(new ScriptInterpreterLocker());
+}
+
 void
 ScriptInterpreter::InitializeInterpreter (SWIGInitCallback python_swig_init_callback)
 {

lldb/source/Interpreter/ScriptInterpreterPython.cpp

@@ -135,6 +135,7 @@ ScriptInterpreterPython::Locker::Locker (ScriptInterpreterPython *py_interpreter
                                          uint16_t on_entry,
                                          uint16_t on_leave,
                                          FILE* wait_msg_handle) :
+    ScriptInterpreterLocker (),
     m_teardown_session( (on_leave & TearDownSession) == TearDownSession ),
     m_python_interpreter(py_interpreter),
     m_tmp_fh(wait_msg_handle)
@@ -2806,6 +2807,15 @@ ScriptInterpreterPython::GetDocumentationForItem(const char* item, std::string&
     }
 }
 
+std::auto_ptr<ScriptInterpreterLocker>
+ScriptInterpreterPython::AcquireInterpreterLock ()
+{
+    std::auto_ptr<ScriptInterpreterLocker> py_lock(new Locker(this,
+                                                              Locker::AcquireLock | Locker::InitSession,
+                                                              Locker::FreeLock | Locker::TearDownSession));
+    return py_lock;
+}
+
 void
 ScriptInterpreterPython::InitializeInterpreter (SWIGInitCallback python_swig_init_callback)
 {