When a user holds an SBFrame reference and then triggers an inferior
function
call (via expression evaluation or GetExtendedBacktraceThread),
variables in
that frame become inaccessible with "register fp is not available"
errors.
This happens because inferior function calls execute through
ThreadPlanCallFunction, which calls ClearStackFrames() during cleanup to
invalidate the unwinder state. ExecutionContextRef objects in the old
SBFrames
were tracking StackFrameLists via weak_ptr, which became stale when
ClearStackFrames() created new instances.
The fix uses stable StackFrameList identifiers that persist across
ClearStackFrames():
- ID = 0: Normal unwinder frames (constant across all instances)
- ID = sequential counter: Scripted frame provider instances
ExecutionContextRef now stores the frame list ID instead of a weak_ptr,
allowing
it to resolve to the current StackFrameList with fresh unwinder state
after an
inferior function call completes.
The Thread object preserves the provider chain configuration
(m_provider_chain_ids and m_next_provider_id) across ClearStackFrames()
so
that recreated StackFrameLists get the same IDs. When providers need to
be
recreated, GetStackFrameList() rebuilds them from the persisted
configuration.
This commit also fixes a deadlock when Python scripted frame providers
call
back into LLDB during frame fetching. The m_list_mutex is now released
before
calling GetFrameAtIndex() on the Python scripted frame provider to
prevent
same-thread deadlock. A dedicated m_unwinder_frames_sp member ensures
GetFrameListByIdentifier(0) always returns the current unwinder frames,
and
proper cleanup in DestroyThread() and ClearStackFrames() to prevent
modules
from lingering after a Thread (and its StackFrameLists) gets destroyed.
Added test validates that variables remain accessible after
GetExtendedBacktraceThread triggers an inferior function call to fetch
libdispatch Queue Info.
rdar://167027676
Signed-off-by: Med Ismail Bennani <ismail@bennani.ma>
This patch adds plumbing to support the implementations of StackFrame::Get{*}Variable{*} on ScriptedFrame. The major pieces required are:
- A modification to ScriptedFrameInterface, so that we can actually call the python methods.
- A corresponding update to the python implementation to call the python methods.
- An implementation in ScriptedFrame that can get the variable list on construction inside ScriptedFrame::Create, and pass that list into the ScriptedFrame so it can get those values on request.
There is a major caveat, which is that if the values from the python side don't have variables attached, right now, they won't be passed into the scripted frame to be stored in the variable list. Future discussions around adding support for 'extended variables' when printing frame variables may create a reason to change the VariableListSP into a ValueObjectListSP, and generate the VariableListSP on the fly, but that should be addressed at a later time.
This patch also adds tests to the frame provider test suite to prove these changes all plumb together correctly.
Related radar: rdar://165708771
This patch extends ScriptedFrame to work with real (non-scripted)
threads,
enabling frame providers to synthesize frames for native processes.
Previously, ScriptedFrame only worked within
ScriptedProcess/ScriptedThread
contexts. This patch decouples ScriptedFrame from ScriptedThread,
allowing
users to augment or replace stack frames in real debugging sessions for
use
cases like custom calling conventions, reconstructing corrupted frames
from
core files, or adding diagnostic frames.
Key changes:
- ScriptedFrame::Create() now accepts ThreadSP instead of requiring
ScriptedThread, extracting architecture from the target triple rather
than ScriptedProcess.arch
- Added SBTarget::RegisterScriptedFrameProvider() and
ClearScriptedFrameProvider() APIs, with Target storing a
SyntheticFrameProviderDescriptor template for new threads
- Added "target frame-provider register/clear" commands for CLI access
- Thread class gains LoadScriptedFrameProvider(),
ClearScriptedFrameProvider(),
and GetFrameProvider() methods for per-thread frame provider management
- New SyntheticStackFrameList overrides FetchFramesUpTo() to lazily
provide
frames from either the frame provider or the real stack
This enables practical use of the SyntheticFrameProvider infrastructure
in
real debugging workflows.
rdar://161834688
Signed-off-by: Med Ismail Bennani <ismail@bennani.ma>
Signed-off-by: Med Ismail Bennani <ismail@bennani.ma>
Med Ismail Bennani