https://github.com/python/cpython/commit/0f02dbe4ab5605dafef150000bdc5a94ad44b3cf commit: 0f02dbe4ab5605dafef150000bdc5a94ad44b3cf branch: 3.14 author: Miss Islington (bot) <[email protected]> committer: colesbury <[email protected]> date: 2026-01-08T12:35:31-05:00 summary:
[3.14] gh-142095: Use thread local frame info in `py-bt` and `py-bt-full` when available (gh-143371) (#143566) In optimized and `-Og` builds, arguments and local variables are frequently unavailable in gdb. This makes `py-bt` fail to print anything useful. Use the `PyThreadState*` pointers `_Py_tss_gilstate` and `Py_tss_tstate` to find the interpreter frame if we can't get the frame from the `_PyEval_EvalFrameDefault` call. (cherry picked from commit 49c3b0a67a77bb42e736cea7dcbc1aa8fa704074) Co-authored-by: Sam Gross <[email protected]> Co-authored-by: Victor Stinner <[email protected]> files: A Misc/NEWS.d/next/Tools-Demos/2026-01-02-11-44-56.gh-issue-142095.4ssgnM.rst M Tools/gdb/libpython.py diff --git a/Misc/NEWS.d/next/Tools-Demos/2026-01-02-11-44-56.gh-issue-142095.4ssgnM.rst b/Misc/NEWS.d/next/Tools-Demos/2026-01-02-11-44-56.gh-issue-142095.4ssgnM.rst new file mode 100644 index 00000000000000..196b27dfd66302 --- /dev/null +++ b/Misc/NEWS.d/next/Tools-Demos/2026-01-02-11-44-56.gh-issue-142095.4ssgnM.rst @@ -0,0 +1,2 @@ +Make gdb 'py-bt' command use frame from thread local state when available. +Patch by Sam Gross and Victor Stinner. diff --git a/Tools/gdb/libpython.py b/Tools/gdb/libpython.py index 27aa6b0cc266d3..a85195dcd1016a 100755 --- a/Tools/gdb/libpython.py +++ b/Tools/gdb/libpython.py @@ -152,6 +152,11 @@ def write(self, data): def getvalue(self): return self._val + +def _PyStackRef_AsPyObjectBorrow(gdbval): + return gdb.Value(int(gdbval['bits']) & ~USED_TAGS) + + class PyObjectPtr(object): """ Class wrapping a gdb.Value that's either a (PyObject*) within the @@ -170,7 +175,7 @@ def __init__(self, gdbval, cast_to=None): if gdbval.type.name == '_PyStackRef': if cast_to is None: cast_to = gdb.lookup_type('PyObject').pointer() - self._gdbval = gdb.Value(int(gdbval['bits']) & ~USED_TAGS).cast(cast_to) + self._gdbval = _PyStackRef_AsPyObjectBorrow(gdbval).cast(cast_to) elif cast_to: self._gdbval = gdbval.cast(cast_to) else: @@ -1034,30 +1039,49 @@ def write_repr(self, out, visited): return return self._frame.write_repr(out, visited) - def print_traceback(self): - if self.is_optimized_out(): - sys.stdout.write(' %s\n' % FRAME_INFO_OPTIMIZED_OUT) - return - return self._frame.print_traceback() - class PyFramePtr: def __init__(self, gdbval): self._gdbval = gdbval + if self.is_optimized_out(): + return + self.co = self._f_code() + if self.is_shim(): + return + self.co_name = self.co.pyop_field('co_name') + self.co_filename = self.co.pyop_field('co_filename') - if not self.is_optimized_out(): + self.f_lasti = self._f_lasti() + self.co_nlocals = int_from_int(self.co.field('co_nlocals')) + pnames = self.co.field('co_localsplusnames') + self.co_localsplusnames = PyTupleObjectPtr.from_pyobject_ptr(pnames) + + @staticmethod + def get_thread_state(): + exprs = [ + '_Py_tss_gilstate', # 3.15+ + '_Py_tss_tstate', # 3.12+ (and not when GIL is released) + 'pthread_getspecific(_PyRuntime.autoTSSkey._key)', # only live programs + '((struct pthread*)$fs_base)->specific_1stblock[_PyRuntime.autoTSSkey._key].data' # x86-64 + ] + for expr in exprs: try: - self.co = self._f_code() - self.co_name = self.co.pyop_field('co_name') - self.co_filename = self.co.pyop_field('co_filename') - - self.f_lasti = self._f_lasti() - self.co_nlocals = int_from_int(self.co.field('co_nlocals')) - pnames = self.co.field('co_localsplusnames') - self.co_localsplusnames = PyTupleObjectPtr.from_pyobject_ptr(pnames) - self._is_code = True - except: - self._is_code = False + val = gdb.parse_and_eval(f'(PyThreadState*)({expr})') + except gdb.error: + continue + if int(val) != 0: + return val + return None + + @staticmethod + def get_thread_local_frame(): + thread_state = PyFramePtr.get_thread_state() + if thread_state is None: + return None + current_frame = thread_state['current_frame'] + if int(current_frame) == 0: + return None + return PyFramePtr(current_frame) def is_optimized_out(self): return self._gdbval.is_optimized_out @@ -1115,6 +1139,8 @@ def is_shim(self): return self._f_special("owner", int) == FRAME_OWNED_BY_INTERPRETER def previous(self): + if int(self._gdbval['previous']) == 0: + return None return self._f_special("previous", PyFramePtr) def iter_globals(self): @@ -1243,6 +1269,27 @@ def print_traceback(self): lineno, self.co_name.proxyval(visited))) + def print_traceback_until_shim(self, frame_index=None): + # Print traceback for _PyInterpreterFrame and return previous frame + interp_frame = self + while True: + if not interp_frame: + sys.stdout.write(' (unable to read python frame information)\n') + return None + if interp_frame.is_shim(): + return interp_frame.previous() + + if frame_index is not None: + line = interp_frame.get_truncated_repr(MAX_OUTPUT_LEN) + sys.stdout.write('#%i %s\n' % (frame_index, line)) + else: + interp_frame.print_traceback() + if not interp_frame.is_optimized_out(): + line = interp_frame.current_line() + if line is not None: + sys.stdout.write(' %s\n' % line.strip()) + interp_frame = interp_frame.previous() + def get_truncated_repr(self, maxlen): ''' Get a repr-like string for the data, but truncate it at "maxlen" bytes @@ -1855,20 +1902,10 @@ def get_selected_bytecode_frame(cls): def print_summary(self): if self.is_evalframe(): interp_frame = self.get_pyop() - while True: - if interp_frame: - if interp_frame.is_shim(): - break - line = interp_frame.get_truncated_repr(MAX_OUTPUT_LEN) - sys.stdout.write('#%i %s\n' % (self.get_index(), line)) - if not interp_frame.is_optimized_out(): - line = interp_frame.current_line() - if line is not None: - sys.stdout.write(' %s\n' % line.strip()) - else: - sys.stdout.write('#%i (unable to read python frame information)\n' % self.get_index()) - break - interp_frame = interp_frame.previous() + if interp_frame: + interp_frame.print_traceback_until_shim(self.get_index()) + else: + sys.stdout.write('#%i (unable to read python frame information)\n' % self.get_index()) else: info = self.is_other_python_frame() if info: @@ -1876,29 +1913,6 @@ def print_summary(self): else: sys.stdout.write('#%i\n' % self.get_index()) - def print_traceback(self): - if self.is_evalframe(): - interp_frame = self.get_pyop() - while True: - if interp_frame: - if interp_frame.is_shim(): - break - interp_frame.print_traceback() - if not interp_frame.is_optimized_out(): - line = interp_frame.current_line() - if line is not None: - sys.stdout.write(' %s\n' % line.strip()) - else: - sys.stdout.write(' (unable to read python frame information)\n') - break - interp_frame = interp_frame.previous() - else: - info = self.is_other_python_frame() - if info: - sys.stdout.write(' %s\n' % info) - else: - sys.stdout.write(' (not a python frame)\n') - class PyList(gdb.Command): '''List the current Python source code, if any @@ -2042,6 +2056,41 @@ def invoke(self, args, from_tty): PyUp() PyDown() + +def print_traceback_helper(full_info): + frame = Frame.get_selected_python_frame() + interp_frame = PyFramePtr.get_thread_local_frame() + if not frame and not interp_frame: + print('Unable to locate python frame') + return + + sys.stdout.write('Traceback (most recent call first):\n') + if frame: + while frame: + frame_index = frame.get_index() if full_info else None + if frame.is_evalframe(): + pyop = frame.get_pyop() + if pyop is not None: + # Use the _PyInterpreterFrame from the gdb frame + interp_frame = pyop + if interp_frame: + interp_frame = interp_frame.print_traceback_until_shim(frame_index) + else: + sys.stdout.write(' (unable to read python frame information)\n') + else: + info = frame.is_other_python_frame() + if full_info: + if info: + sys.stdout.write('#%i %s\n' % (frame_index, info)) + elif info: + sys.stdout.write(' %s\n' % info) + frame = frame.older() + else: + # Fall back to just using the thread-local frame + while interp_frame: + interp_frame = interp_frame.print_traceback_until_shim() + + class PyBacktraceFull(gdb.Command): 'Display the current python frame and all the frames within its call stack (if any)' def __init__(self): @@ -2052,15 +2101,7 @@ def __init__(self): def invoke(self, args, from_tty): - frame = Frame.get_selected_python_frame() - if not frame: - print('Unable to locate python frame') - return - - while frame: - if frame.is_python_frame(): - frame.print_summary() - frame = frame.older() + print_traceback_helper(full_info=True) PyBacktraceFull() @@ -2072,18 +2113,8 @@ def __init__(self): gdb.COMMAND_STACK, gdb.COMPLETE_NONE) - def invoke(self, args, from_tty): - frame = Frame.get_selected_python_frame() - if not frame: - print('Unable to locate python frame') - return - - sys.stdout.write('Traceback (most recent call first):\n') - while frame: - if frame.is_python_frame(): - frame.print_traceback() - frame = frame.older() + print_traceback_helper(full_info=False) PyBacktrace() _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
