Modules/_remote_debugging/frames.c - external/github.com/python/cpython - Git at Google

 /******************************************************************************
  * Remote Debugging Module - Frame Functions
  *
  * This file contains functions for parsing interpreter frames and
  * managing stack chunks from remote process memory.
  ******************************************************************************/

 #include "_remote_debugging.h"

 /* ============================================================================
  * STACK CHUNK MANAGEMENT FUNCTIONS
  * ============================================================================ */

 void
 cleanup_stack_chunks(StackChunkList *chunks)
 {
     for (size_t i = 0; i < chunks->count; ++i) {
         PyMem_RawFree(chunks->chunks[i].local_copy);
     }
     PyMem_RawFree(chunks->chunks);
 }

 static int
 process_single_stack_chunk(
     RemoteUnwinderObject *unwinder,
     uintptr_t chunk_addr,
     StackChunkInfo *chunk_info
 ) {
     // Start with default size assumption
     size_t current_size = _PY_DATA_STACK_CHUNK_SIZE;

     char *this_chunk = PyMem_RawMalloc(current_size);
     if (!this_chunk) {
         PyErr_NoMemory();
         set_exception_cause(unwinder, PyExc_MemoryError, "Failed to allocate stack chunk buffer");
         return -1;
     }

     if (_Py_RemoteDebug_PagedReadRemoteMemory(&unwinder->handle, chunk_addr, current_size, this_chunk) < 0) {
         PyMem_RawFree(this_chunk);
         set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to read stack chunk");
         return -1;
     }

     // Check actual size and reread if necessary
     size_t actual_size = GET_MEMBER(size_t, this_chunk, offsetof(_PyStackChunk, size));
     if (actual_size != current_size) {
         this_chunk = PyMem_RawRealloc(this_chunk, actual_size);
         if (!this_chunk) {
             PyErr_NoMemory();
             set_exception_cause(unwinder, PyExc_MemoryError, "Failed to reallocate stack chunk buffer");
             return -1;
         }

         if (_Py_RemoteDebug_PagedReadRemoteMemory(&unwinder->handle, chunk_addr, actual_size, this_chunk) < 0) {
             PyMem_RawFree(this_chunk);
             set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to reread stack chunk with correct size");
             return -1;
         }
         current_size = actual_size;
     }

     chunk_info->remote_addr = chunk_addr;
     chunk_info->size = current_size;
     chunk_info->local_copy = this_chunk;
     return 0;
 }

 int
 copy_stack_chunks(RemoteUnwinderObject *unwinder,
                   uintptr_t tstate_addr,
                   StackChunkList *out_chunks)
 {
     uintptr_t chunk_addr;
     StackChunkInfo *chunks = NULL;
     size_t count = 0;
     size_t max_chunks = 16;

     if (read_ptr(unwinder, tstate_addr + (uintptr_t)unwinder->debug_offsets.thread_state.datastack_chunk, &chunk_addr)) {
         set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to read initial stack chunk address");
         return -1;
     }

     chunks = PyMem_RawMalloc(max_chunks * sizeof(StackChunkInfo));
     if (!chunks) {
         PyErr_NoMemory();
         set_exception_cause(unwinder, PyExc_MemoryError, "Failed to allocate stack chunks array");
         return -1;
     }

     while (chunk_addr != 0) {
         // Grow array if needed
         if (count >= max_chunks) {
             max_chunks *= 2;
             StackChunkInfo *new_chunks = PyMem_RawRealloc(chunks, max_chunks * sizeof(StackChunkInfo));
             if (!new_chunks) {
                 PyErr_NoMemory();
                 set_exception_cause(unwinder, PyExc_MemoryError, "Failed to grow stack chunks array");
                 goto error;
             }
             chunks = new_chunks;
         }

         // Process this chunk
         if (process_single_stack_chunk(unwinder, chunk_addr, &chunks[count]) < 0) {
             set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to process stack chunk");
             goto error;
         }

         // Get next chunk address and increment count
         chunk_addr = GET_MEMBER(uintptr_t, chunks[count].local_copy, offsetof(_PyStackChunk, previous));
         count++;
     }

     out_chunks->chunks = chunks;
     out_chunks->count = count;
     return 0;

 error:
     for (size_t i = 0; i < count; ++i) {
         PyMem_RawFree(chunks[i].local_copy);
     }
     PyMem_RawFree(chunks);
     return -1;
 }

 void *
 find_frame_in_chunks(StackChunkList *chunks, uintptr_t remote_ptr)
 {
     for (size_t i = 0; i < chunks->count; ++i) {
         uintptr_t base = chunks->chunks[i].remote_addr + offsetof(_PyStackChunk, data);
         size_t payload = chunks->chunks[i].size - offsetof(_PyStackChunk, data);

         if (remote_ptr >= base && remote_ptr < base + payload) {
             return (char *)chunks->chunks[i].local_copy + (remote_ptr - chunks->chunks[i].remote_addr);
         }
     }
     return NULL;
 }

 /* ============================================================================
  * FRAME PARSING FUNCTIONS
  * ============================================================================ */

 int
 is_frame_valid(
     RemoteUnwinderObject *unwinder,
     uintptr_t frame_addr,
     uintptr_t code_object_addr
 ) {
     if ((void*)code_object_addr == NULL) {
         return 0;
     }

     void* frame = (void*)frame_addr;

     if (GET_MEMBER(char, frame, unwinder->debug_offsets.interpreter_frame.owner) == FRAME_OWNED_BY_INTERPRETER) {
         return 0;  // C frame
     }

     if (GET_MEMBER(char, frame, unwinder->debug_offsets.interpreter_frame.owner) != FRAME_OWNED_BY_GENERATOR
         && GET_MEMBER(char, frame, unwinder->debug_offsets.interpreter_frame.owner) != FRAME_OWNED_BY_THREAD) {
         PyErr_Format(PyExc_RuntimeError, "Unhandled frame owner %d.\n",
                     GET_MEMBER(char, frame, unwinder->debug_offsets.interpreter_frame.owner));
         set_exception_cause(unwinder, PyExc_RuntimeError, "Unhandled frame owner type in async frame");
         return -1;
     }
     return 1;
 }

 int
 parse_frame_object(
     RemoteUnwinderObject *unwinder,
     PyObject** result,
     uintptr_t address,
     uintptr_t* address_of_code_object,
     uintptr_t* previous_frame
 ) {
     char frame[SIZEOF_INTERP_FRAME];
     *address_of_code_object = 0;

     Py_ssize_t bytes_read = _Py_RemoteDebug_PagedReadRemoteMemory(
         &unwinder->handle,
         address,
         SIZEOF_INTERP_FRAME,
         frame
     );
     if (bytes_read < 0) {
         set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to read interpreter frame");
         return -1;
     }

     *previous_frame = GET_MEMBER(uintptr_t, frame, unwinder->debug_offsets.interpreter_frame.previous);
     uintptr_t code_object = GET_MEMBER_NO_TAG(uintptr_t, frame, unwinder->debug_offsets.interpreter_frame.executable);
     int frame_valid = is_frame_valid(unwinder, (uintptr_t)frame, code_object);
     if (frame_valid != 1) {
         return frame_valid;
     }

     uintptr_t instruction_pointer = GET_MEMBER(uintptr_t, frame, unwinder->debug_offsets.interpreter_frame.instr_ptr);

     // Get tlbc_index for free threading builds
     int32_t tlbc_index = 0;
 #ifdef Py_GIL_DISABLED
     if (unwinder->debug_offsets.interpreter_frame.tlbc_index != 0) {
         tlbc_index = GET_MEMBER(int32_t, frame, unwinder->debug_offsets.interpreter_frame.tlbc_index);
     }
 #endif

     *address_of_code_object = code_object;
     return parse_code_object(unwinder, result, code_object, instruction_pointer, previous_frame, tlbc_index);
 }

 int
 parse_frame_from_chunks(
     RemoteUnwinderObject *unwinder,
     PyObject **result,
     uintptr_t address,
     uintptr_t *previous_frame,
     uintptr_t *stackpointer,
     StackChunkList *chunks
 ) {
     void *frame_ptr = find_frame_in_chunks(chunks, address);
     if (!frame_ptr) {
         set_exception_cause(unwinder, PyExc_RuntimeError, "Frame not found in stack chunks");
         return -1;
     }

     char *frame = (char *)frame_ptr;
     *previous_frame = GET_MEMBER(uintptr_t, frame, unwinder->debug_offsets.interpreter_frame.previous);
     *stackpointer = GET_MEMBER(uintptr_t, frame, unwinder->debug_offsets.interpreter_frame.stackpointer);
     uintptr_t code_object = GET_MEMBER_NO_TAG(uintptr_t, frame_ptr, unwinder->debug_offsets.interpreter_frame.executable);
     int frame_valid = is_frame_valid(unwinder, (uintptr_t)frame, code_object);
     if (frame_valid != 1) {
         return frame_valid;
     }

     uintptr_t instruction_pointer = GET_MEMBER(uintptr_t, frame, unwinder->debug_offsets.interpreter_frame.instr_ptr);

     // Get tlbc_index for free threading builds
     int32_t tlbc_index = 0;
 #ifdef Py_GIL_DISABLED
     if (unwinder->debug_offsets.interpreter_frame.tlbc_index != 0) {
         tlbc_index = GET_MEMBER(int32_t, frame, unwinder->debug_offsets.interpreter_frame.tlbc_index);
     }
 #endif

     return parse_code_object(unwinder, result, code_object, instruction_pointer, previous_frame, tlbc_index);
 }

 /* ============================================================================
  * FRAME CHAIN PROCESSING
  * ============================================================================ */

 int
 process_frame_chain(
     RemoteUnwinderObject *unwinder,
     uintptr_t initial_frame_addr,
     StackChunkList *chunks,
     PyObject *frame_info,
     uintptr_t gc_frame)
 {
     uintptr_t frame_addr = initial_frame_addr;
     uintptr_t prev_frame_addr = 0;
     const size_t MAX_FRAMES = 1024;
     size_t frame_count = 0;

     while ((void*)frame_addr != NULL) {
         PyObject *frame = NULL;
         uintptr_t next_frame_addr = 0;
         uintptr_t stackpointer = 0;

         if (++frame_count > MAX_FRAMES) {
             PyErr_SetString(PyExc_RuntimeError, "Too many stack frames (possible infinite loop)");
             set_exception_cause(unwinder, PyExc_RuntimeError, "Frame chain iteration limit exceeded");
             return -1;
         }

         // Try chunks first, fallback to direct memory read
         if (parse_frame_from_chunks(unwinder, &frame, frame_addr, &next_frame_addr, &stackpointer, chunks) < 0) {
             PyErr_Clear();
             uintptr_t address_of_code_object = 0;
             if (parse_frame_object(unwinder, &frame, frame_addr, &address_of_code_object ,&next_frame_addr) < 0) {
                 set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to parse frame object in chain");
                 return -1;
             }
         }
         if (frame == NULL && PyList_GET_SIZE(frame_info) == 0) {
             // If the first frame is missing, the chain is broken:
             const char *e = "Failed to parse initial frame in chain";
             PyErr_SetString(PyExc_RuntimeError, e);
             return -1;
         }
         PyObject *extra_frame = NULL;
         // This frame kicked off the current GC collection:
         if (unwinder->gc && frame_addr == gc_frame) {
             _Py_DECLARE_STR(gc, "<GC>");
             extra_frame = &_Py_STR(gc);
         }
         // Otherwise, check for native frames to insert:
         else if (unwinder->native &&
                  // We've reached an interpreter trampoline frame:
                  frame == NULL &&
                  // Bottommost frame is always native, so skip that one:
                  next_frame_addr &&
                  // Only suppress native frames if GC tracking is enabled and the next frame will be a GC frame:
                  !(unwinder->gc && next_frame_addr == gc_frame))
         {
             _Py_DECLARE_STR(native, "<native>");
             extra_frame = &_Py_STR(native);
         }
         if (extra_frame) {
             // Use "~" as file and 0 as line, since that's what pstats uses:
             PyObject *extra_frame_info = make_frame_info(
                 unwinder, _Py_LATIN1_CHR('~'), _PyLong_GetZero(), extra_frame);
             if (extra_frame_info == NULL) {
                 return -1;
             }
             int error = PyList_Append(frame_info, extra_frame_info);
             Py_DECREF(extra_frame_info);
             if (error) {
                 const char *e = "Failed to append extra frame to frame info list";
                 set_exception_cause(unwinder, PyExc_RuntimeError, e);
                 return -1;
             }
         }
         if (frame) {
             if (prev_frame_addr && frame_addr != prev_frame_addr) {
                 const char *f = "Broken frame chain: expected frame at 0x%lx, got 0x%lx";
                 PyErr_Format(PyExc_RuntimeError, f, prev_frame_addr, frame_addr);
                 Py_DECREF(frame);
                 const char *e = "Frame chain consistency check failed";
                 set_exception_cause(unwinder, PyExc_RuntimeError, e);
                 return -1;
             }

             if (PyList_Append(frame_info, frame) == -1) {
                 Py_DECREF(frame);
                 const char *e = "Failed to append frame to frame info list";
                 set_exception_cause(unwinder, PyExc_RuntimeError, e);
                 return -1;
             }
             Py_DECREF(frame);
         }

         prev_frame_addr = next_frame_addr;
         frame_addr = next_frame_addr;
     }

     return 0;
 }
	/******************************************************************************
	* Remote Debugging Module - Frame Functions
	*
	* This file contains functions for parsing interpreter frames and
	* managing stack chunks from remote process memory.
	******************************************************************************/

	#include "_remote_debugging.h"

	/* ============================================================================
	* STACK CHUNK MANAGEMENT FUNCTIONS
	* ============================================================================ */

	void
	cleanup_stack_chunks(StackChunkList *chunks)
	{
	for (size_t i = 0; i < chunks->count; ++i) {
	PyMem_RawFree(chunks->chunks[i].local_copy);
	}
	PyMem_RawFree(chunks->chunks);
	}

	static int
	process_single_stack_chunk(
	RemoteUnwinderObject *unwinder,
	uintptr_t chunk_addr,
	StackChunkInfo *chunk_info
	) {
	// Start with default size assumption
	size_t current_size = _PY_DATA_STACK_CHUNK_SIZE;

	char *this_chunk = PyMem_RawMalloc(current_size);
	if (!this_chunk) {
	PyErr_NoMemory();
	set_exception_cause(unwinder, PyExc_MemoryError, "Failed to allocate stack chunk buffer");
	return -1;
	}

	if (_Py_RemoteDebug_PagedReadRemoteMemory(&unwinder->handle, chunk_addr, current_size, this_chunk) < 0) {
	PyMem_RawFree(this_chunk);
	set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to read stack chunk");
	return -1;
	}

	// Check actual size and reread if necessary
	size_t actual_size = GET_MEMBER(size_t, this_chunk, offsetof(_PyStackChunk, size));
	if (actual_size != current_size) {
	this_chunk = PyMem_RawRealloc(this_chunk, actual_size);
	if (!this_chunk) {
	PyErr_NoMemory();
	set_exception_cause(unwinder, PyExc_MemoryError, "Failed to reallocate stack chunk buffer");
	return -1;
	}

	if (_Py_RemoteDebug_PagedReadRemoteMemory(&unwinder->handle, chunk_addr, actual_size, this_chunk) < 0) {
	PyMem_RawFree(this_chunk);
	set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to reread stack chunk with correct size");
	return -1;
	}
	current_size = actual_size;
	}

	chunk_info->remote_addr = chunk_addr;
	chunk_info->size = current_size;
	chunk_info->local_copy = this_chunk;
	return 0;
	}

	int
	copy_stack_chunks(RemoteUnwinderObject *unwinder,
	uintptr_t tstate_addr,
	StackChunkList *out_chunks)
	{
	uintptr_t chunk_addr;
	StackChunkInfo *chunks = NULL;
	size_t count = 0;
	size_t max_chunks = 16;

	if (read_ptr(unwinder, tstate_addr + (uintptr_t)unwinder->debug_offsets.thread_state.datastack_chunk, &chunk_addr)) {
	set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to read initial stack chunk address");
	return -1;
	}

	chunks = PyMem_RawMalloc(max_chunks * sizeof(StackChunkInfo));
	if (!chunks) {
	PyErr_NoMemory();
	set_exception_cause(unwinder, PyExc_MemoryError, "Failed to allocate stack chunks array");
	return -1;
	}

	while (chunk_addr != 0) {
	// Grow array if needed
	if (count >= max_chunks) {
	max_chunks *= 2;
	StackChunkInfo new_chunks = PyMem_RawRealloc(chunks, max_chunks sizeof(StackChunkInfo));
	if (!new_chunks) {
	PyErr_NoMemory();
	set_exception_cause(unwinder, PyExc_MemoryError, "Failed to grow stack chunks array");
	goto error;
	}
	chunks = new_chunks;
	}

	// Process this chunk
	if (process_single_stack_chunk(unwinder, chunk_addr, &chunks[count]) < 0) {
	set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to process stack chunk");
	goto error;
	}

	// Get next chunk address and increment count
	chunk_addr = GET_MEMBER(uintptr_t, chunks[count].local_copy, offsetof(_PyStackChunk, previous));
	count++;
	}

	out_chunks->chunks = chunks;
	out_chunks->count = count;
	return 0;

	error:
	for (size_t i = 0; i < count; ++i) {
	PyMem_RawFree(chunks[i].local_copy);
	}
	PyMem_RawFree(chunks);
	return -1;
	}

	void *
	find_frame_in_chunks(StackChunkList *chunks, uintptr_t remote_ptr)
	{
	for (size_t i = 0; i < chunks->count; ++i) {
	uintptr_t base = chunks->chunks[i].remote_addr + offsetof(_PyStackChunk, data);
	size_t payload = chunks->chunks[i].size - offsetof(_PyStackChunk, data);

	if (remote_ptr >= base && remote_ptr < base + payload) {
	return (char *)chunks->chunks[i].local_copy + (remote_ptr - chunks->chunks[i].remote_addr);
	}
	}
	return NULL;
	}

	/* ============================================================================
	* FRAME PARSING FUNCTIONS
	* ============================================================================ */

	int
	is_frame_valid(
	RemoteUnwinderObject *unwinder,
	uintptr_t frame_addr,
	uintptr_t code_object_addr
	) {
	if ((void*)code_object_addr == NULL) {
	return 0;
	}

	void* frame = (void*)frame_addr;

	if (GET_MEMBER(char, frame, unwinder->debug_offsets.interpreter_frame.owner) == FRAME_OWNED_BY_INTERPRETER) {
	return 0; // C frame
	}

	if (GET_MEMBER(char, frame, unwinder->debug_offsets.interpreter_frame.owner) != FRAME_OWNED_BY_GENERATOR
	&& GET_MEMBER(char, frame, unwinder->debug_offsets.interpreter_frame.owner) != FRAME_OWNED_BY_THREAD) {
	PyErr_Format(PyExc_RuntimeError, "Unhandled frame owner %d.\n",
	GET_MEMBER(char, frame, unwinder->debug_offsets.interpreter_frame.owner));
	set_exception_cause(unwinder, PyExc_RuntimeError, "Unhandled frame owner type in async frame");
	return -1;
	}
	return 1;
	}

	int
	parse_frame_object(
	RemoteUnwinderObject *unwinder,
	PyObject** result,
	uintptr_t address,
	uintptr_t* address_of_code_object,
	uintptr_t* previous_frame
	) {
	char frame[SIZEOF_INTERP_FRAME];
	*address_of_code_object = 0;

	Py_ssize_t bytes_read = _Py_RemoteDebug_PagedReadRemoteMemory(
	&unwinder->handle,
	address,
	SIZEOF_INTERP_FRAME,
	frame
	);
	if (bytes_read < 0) {
	set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to read interpreter frame");
	return -1;
	}

	*previous_frame = GET_MEMBER(uintptr_t, frame, unwinder->debug_offsets.interpreter_frame.previous);
	uintptr_t code_object = GET_MEMBER_NO_TAG(uintptr_t, frame, unwinder->debug_offsets.interpreter_frame.executable);
	int frame_valid = is_frame_valid(unwinder, (uintptr_t)frame, code_object);
	if (frame_valid != 1) {
	return frame_valid;
	}

	uintptr_t instruction_pointer = GET_MEMBER(uintptr_t, frame, unwinder->debug_offsets.interpreter_frame.instr_ptr);

	// Get tlbc_index for free threading builds
	int32_t tlbc_index = 0;
	#ifdef Py_GIL_DISABLED
	if (unwinder->debug_offsets.interpreter_frame.tlbc_index != 0) {
	tlbc_index = GET_MEMBER(int32_t, frame, unwinder->debug_offsets.interpreter_frame.tlbc_index);
	}
	#endif

	*address_of_code_object = code_object;
	return parse_code_object(unwinder, result, code_object, instruction_pointer, previous_frame, tlbc_index);
	}

	int
	parse_frame_from_chunks(
	RemoteUnwinderObject *unwinder,
	PyObject **result,
	uintptr_t address,
	uintptr_t *previous_frame,
	uintptr_t *stackpointer,
	StackChunkList *chunks
	) {
	void *frame_ptr = find_frame_in_chunks(chunks, address);
	if (!frame_ptr) {
	set_exception_cause(unwinder, PyExc_RuntimeError, "Frame not found in stack chunks");
	return -1;
	}

	char frame = (char )frame_ptr;
	*previous_frame = GET_MEMBER(uintptr_t, frame, unwinder->debug_offsets.interpreter_frame.previous);
	*stackpointer = GET_MEMBER(uintptr_t, frame, unwinder->debug_offsets.interpreter_frame.stackpointer);
	uintptr_t code_object = GET_MEMBER_NO_TAG(uintptr_t, frame_ptr, unwinder->debug_offsets.interpreter_frame.executable);
	int frame_valid = is_frame_valid(unwinder, (uintptr_t)frame, code_object);
	if (frame_valid != 1) {
	return frame_valid;
	}

	uintptr_t instruction_pointer = GET_MEMBER(uintptr_t, frame, unwinder->debug_offsets.interpreter_frame.instr_ptr);

	// Get tlbc_index for free threading builds
	int32_t tlbc_index = 0;
	#ifdef Py_GIL_DISABLED
	if (unwinder->debug_offsets.interpreter_frame.tlbc_index != 0) {
	tlbc_index = GET_MEMBER(int32_t, frame, unwinder->debug_offsets.interpreter_frame.tlbc_index);
	}
	#endif

	return parse_code_object(unwinder, result, code_object, instruction_pointer, previous_frame, tlbc_index);
	}

	/* ============================================================================
	* FRAME CHAIN PROCESSING
	* ============================================================================ */

	int
	process_frame_chain(
	RemoteUnwinderObject *unwinder,
	uintptr_t initial_frame_addr,
	StackChunkList *chunks,
	PyObject *frame_info,
	uintptr_t gc_frame)
	{
	uintptr_t frame_addr = initial_frame_addr;
	uintptr_t prev_frame_addr = 0;
	const size_t MAX_FRAMES = 1024;
	size_t frame_count = 0;

	while ((void*)frame_addr != NULL) {
	PyObject *frame = NULL;
	uintptr_t next_frame_addr = 0;
	uintptr_t stackpointer = 0;

	if (++frame_count > MAX_FRAMES) {
	PyErr_SetString(PyExc_RuntimeError, "Too many stack frames (possible infinite loop)");
	set_exception_cause(unwinder, PyExc_RuntimeError, "Frame chain iteration limit exceeded");
	return -1;
	}

	// Try chunks first, fallback to direct memory read
	if (parse_frame_from_chunks(unwinder, &frame, frame_addr, &next_frame_addr, &stackpointer, chunks) < 0) {
	PyErr_Clear();
	uintptr_t address_of_code_object = 0;
	if (parse_frame_object(unwinder, &frame, frame_addr, &address_of_code_object ,&next_frame_addr) < 0) {
	set_exception_cause(unwinder, PyExc_RuntimeError, "Failed to parse frame object in chain");
	return -1;
	}
	}
	if (frame == NULL && PyList_GET_SIZE(frame_info) == 0) {
	// If the first frame is missing, the chain is broken:
	const char *e = "Failed to parse initial frame in chain";
	PyErr_SetString(PyExc_RuntimeError, e);
	return -1;
	}
	PyObject *extra_frame = NULL;
	// This frame kicked off the current GC collection:
	if (unwinder->gc && frame_addr == gc_frame) {
	_Py_DECLARE_STR(gc, "<GC>");
	extra_frame = &_Py_STR(gc);
	}
	// Otherwise, check for native frames to insert:
	else if (unwinder->native &&
	// We've reached an interpreter trampoline frame:
	frame == NULL &&
	// Bottommost frame is always native, so skip that one:
	next_frame_addr &&
	// Only suppress native frames if GC tracking is enabled and the next frame will be a GC frame:
	!(unwinder->gc && next_frame_addr == gc_frame))
	{
	_Py_DECLARE_STR(native, "<native>");
	extra_frame = &_Py_STR(native);
	}
	if (extra_frame) {
	// Use "~" as file and 0 as line, since that's what pstats uses:
	PyObject *extra_frame_info = make_frame_info(
	unwinder, _Py_LATIN1_CHR('~'), _PyLong_GetZero(), extra_frame);
	if (extra_frame_info == NULL) {
	return -1;
	}
	int error = PyList_Append(frame_info, extra_frame_info);
	Py_DECREF(extra_frame_info);
	if (error) {
	const char *e = "Failed to append extra frame to frame info list";
	set_exception_cause(unwinder, PyExc_RuntimeError, e);
	return -1;
	}
	}
	if (frame) {
	if (prev_frame_addr && frame_addr != prev_frame_addr) {
	const char *f = "Broken frame chain: expected frame at 0x%lx, got 0x%lx";
	PyErr_Format(PyExc_RuntimeError, f, prev_frame_addr, frame_addr);
	Py_DECREF(frame);
	const char *e = "Frame chain consistency check failed";
	set_exception_cause(unwinder, PyExc_RuntimeError, e);
	return -1;
	}

	if (PyList_Append(frame_info, frame) == -1) {
	Py_DECREF(frame);
	const char *e = "Failed to append frame to frame info list";
	set_exception_cause(unwinder, PyExc_RuntimeError, e);
	return -1;
	}
	Py_DECREF(frame);
	}

	prev_frame_addr = next_frame_addr;
	frame_addr = next_frame_addr;
	}

	return 0;
	}