ScriptedFrameProvider#

class lldb.plugins.scripted_frame_provider.ScriptedFrameProvider(input_frames, args)#

The base class for a scripted frame provider.

A scripted frame provider allows you to provide custom stack frames for a thread, which can be used to augment or replace the standard unwinding mechanism. This is useful for:

Providing frames for custom calling conventions or languages
Reconstructing missing frames from crash dumps or core files
Adding diagnostic or synthetic frames for debugging
Visualizing state machines or async execution contexts

Most of the base class methods are @abstractmethod that need to be overwritten by the inheriting class.

The constructor of this class sets up the following attributes:

input_frames (lldb.SBFrameList or None): The frame list to use as input
thread (lldb.SBThread or None): The thread this provider is attached to.
process (lldb.SBProcess or None): The process that owns the thread.
target (lldb.SBTarget or None): The target from the thread’s process.
args (lldb.SBStructuredData or None): Dictionary-like structured data passed when the provider was registered.

Example usage:

from lldb.plugins.scripted_frame_provider import ScriptedFrameProvider

class MyFrameProvider(ScriptedFrameProvider):
    def __init__(self, input_frames, args):
        super().__init__(input_frames, args)

    @staticmethod
    def get_description():
        return "Show each frame twice"

    def get_frame_at_index(self, index):
        # Duplicate every frame
        return int(index / 2)

def __lldb_init_module(debugger, internal_dict):
    debugger.HandleCommand(f"target frame-provider register -C {__name__}.MyFrameProvider")

if __name__ == '__main__':
    print("This script should be loaded from LLDB using `command script import <filename>`")

You can register your frame provider either via the CLI command target frame-provider register or via the API SBThread.RegisterScriptedFrameProvider.

Methods Summary

`applies_to_thread`(thread)	Determine if this frame provider should be used for a given thread.
`get_description`()	Get a description of this frame provider.
`get_frame_at_index`(index)	Get a single stack frame at the given index.
`get_priority`()	Get the priority of this frame provider.

Methods Documentation

static applies_to_thread(thread)#

Determine if this frame provider should be used for a given thread.

This static method is called before creating an instance of the frame provider to determine if it should be applied to a specific thread. Override this method to provide custom filtering logic.

Parameters:

thread (lldb.SBThread) – The thread to check.

Returns:

True if this frame provider should be used for the thread,: False otherwise. The default implementation returns True for all threads.

Return type:

bool

Example:

@staticmethod
def applies_to_thread(thread):
    # Only apply to thread 1
    return thread.GetIndexID() == 1

abstract static get_description()#

Get a description of this frame provider.

This method should return a human-readable string describing what this frame provider does. The description is used for debugging and display purposes.

Returns:: A description of the frame provider.
Return type:: str

Example:

@staticmethod
def get_description(self):
    return "Crash log frame provider for thread 1"

abstract get_frame_at_index(index)#

Get a single stack frame at the given index.

This method is called lazily when a specific frame is needed in the thread’s backtrace (e.g., via the ‘bt’ command). Each frame is requested individually as needed.

Parameters:

index (int) – The frame index to retrieve (0 for youngest/top frame).

Returns:

An object describing the stack: stack frame, or None if no frame exists at this index.

An integer represents the corresponding input frame index to reuse, in case you want to just forward an frame from the input_frames.

Returning a ScriptedFrame object injects artificial frames giving you full control over the frame behavior.

Returning a dictionary also injects an artificial frame, but with less control over the frame behavior. The dictionary must contain:

idx (int): The synthetic frame index (0 for youngest/top frame)
pc (int): The program counter address for the synthetic frame

Return type:

ScriptedFrame, integer, Dict or None

Example:

def get_frame_at_index(self, index):
    # Return None when there are no more frames
    if index >= self.total_frames:
        return None

    # Re-use an input frame by returning its index
    if self.should_use_input_frame(index):
        return index  # Returns input frame at this index

    # Or create a custom frame dictionary
    if index == 0:
        return {
            "idx": 0,
            "pc": 0x100001234,
        }

    return None

Note

The frames are indexed from 0 (youngest/top) to N (oldest/bottom). This method will be called repeatedly with increasing indices until None is returned.

static get_priority()#

Get the priority of this frame provider.

This static method is called to determine the evaluation order when multiple frame providers could apply to the same thread. Lower numbers indicate higher priority (like Unix nice values).

Returns:

Priority value where 0 is highest priority.: Return None for default priority (UINT32_MAX - lowest priority).

Return type:

int or None

Example:

@staticmethod
def get_priority():
    # High priority - runs before most providers
    return 10

@staticmethod
def get_priority():
    # Default priority - runs last
    return None