[lldb] Introduce ScriptedFrame affordance (#149622)

This patch introduces a new scripting affordance in lldb:
`ScriptedFrame`.

This allows user to produce mock stackframes in scripted threads and
scripted processes from a python script.

With this change, StackFrame can be synthetized from different sources:
- Either from a dictionary containing a load address, and a frame index,
  which is the legacy way.
- Or by creating a ScriptedFrame python object.

One particularity of synthezising stackframes from the ScriptedFrame
python object, is that these frame have an optional PC, meaning that
they don't have a report a valid PC and they can act as shells that just
contain static information, like the frame function name, the list of
variables or registers, etc. It can also provide a symbol context.

rdar://157260006

Signed-off-by: Med Ismail Bennani <ismail@bennani.ma>

Signed-off-by: Med Ismail Bennani <ismail@bennani.ma>

1 files changed, 136 insertions, 0 deletions

diff --git a/lldb/examples/python/templates/scripted_process.py b/lldb/examples/python/templates/scripted_process.py
index b6360b851907..49059d533f38 100644
--- a/lldb/examples/python/templates/scripted_process.py
+++ b/lldb/examples/python/templates/scripted_process.py
@@ -383,6 +383,142 @@ class ScriptedThread(metaclass=ABCMeta):
         """
         return self.extended_info
 
+    def get_scripted_frame_plugin(self):
+        """Get scripted frame plugin name.
+
+        Returns:
+            str: Name of the scripted frame plugin.
+        """
+        return None
+
+
+class ScriptedFrame(metaclass=ABCMeta):
+    """
+    The base class for a scripted frame.
+
+    Most of the base class methods are `@abstractmethod` that need to be
+    overwritten by the inheriting class.
+    """
+
+    @abstractmethod
+    def __init__(self, thread, args):
+        """Construct a scripted frame.
+
+        Args:
+            thread (ScriptedThread): The thread owning this frame.
+            args (lldb.SBStructuredData): A Dictionary holding arbitrary
+                key/value pairs used by the scripted frame.
+        """
+        self.target = None
+        self.originating_thread = None
+        self.thread = None
+        self.args = None
+        self.id = None
+        self.name = None
+        self.register_info = None
+        self.register_ctx = {}
+        self.variables = []
+
+        if (
+            isinstance(thread, ScriptedThread)
+            or isinstance(thread, lldb.SBThread)
+            and thread.IsValid()
+        ):
+            self.target = thread.target
+            self.process = thread.process
+            self.originating_thread = thread
+            self.thread = self.process.GetThreadByIndexID(thread.tid)
+            self.get_register_info()
+
+    @abstractmethod
+    def get_id(self):
+        """Get the scripted frame identifier.
+
+        Returns:
+            int: The identifier of the scripted frame in the scripted thread.
+        """
+        pass
+
+    def get_pc(self):
+        """Get the scripted frame address.
+
+        Returns:
+            int: The optional address of the scripted frame in the scripted thread.
+        """
+        return None
+
+    def get_symbol_context(self):
+        """Get the scripted frame symbol context.
+
+        Returns:
+            lldb.SBSymbolContext: The symbol context of the scripted frame in the scripted thread.
+        """
+        return None
+
+    def is_inlined(self):
+        """Check if the scripted frame is inlined.
+
+        Returns:
+            bool: True if scripted frame is inlined. False otherwise.
+        """
+        return False
+
+    def is_artificial(self):
+        """Check if the scripted frame is artificial.
+
+        Returns:
+            bool: True if scripted frame is artificial. False otherwise.
+        """
+        return True
+
+    def is_hidden(self):
+        """Check if the scripted frame is hidden.
+
+        Returns:
+            bool: True if scripted frame is hidden. False otherwise.
+        """
+        return False
+
+    def get_function_name(self):
+        """Get the scripted frame function name.
+
+        Returns:
+            str: The function name of the scripted frame.
+        """
+        return self.name
+
+    def get_display_function_name(self):
+        """Get the scripted frame display function name.
+
+        Returns:
+            str: The display function name of the scripted frame.
+        """
+        return self.get_function_name()
+
+    def get_variables(self, filters):
+        """Get the scripted thread state type.
+
+        Args:
+            filter (lldb.SBVariablesOptions): The filter used to resolve the variables
+        Returns:
+            lldb.SBValueList: The SBValueList containing the SBValue for each resolved variable.
+                              Returns None by default.
+        """
+        return None
+
+    def get_register_info(self):
+        if self.register_info is None:
+            self.register_info = self.originating_thread.get_register_info()
+        return self.register_info
+
+    @abstractmethod
+    def get_register_context(self):
+        """Get the scripted thread register context
+
+        Returns:
+            str: A byte representing all register's value.
+        """
+        pass
 
 class PassthroughScriptedProcess(ScriptedProcess):
     driving_target = None