fix(profiling): remove unnecessary access to frame.f_locals [backport 3.19]

ddtrace/profiling/collector/_memalloc_tb.cpp

@@ -13,8 +13,6 @@
 /* A string containing "<unknown>" just in case we can't store the real function
  * or file name. */
 static PyObject* unknown_name = NULL;
-/* A string containing "" */
-static PyObject* empty_string = NULL;
 
 #define TRACEBACK_SIZE(NFRAME) (sizeof(traceback_t) + sizeof(frame_t) * (NFRAME - 1))
 
@@ -135,12 +133,6 @@ memalloc_tb_init(uint16_t max_nframe)
         PyUnicode_InternInPlace(&unknown_name);
     }
 
-    if (empty_string == NULL) {
-        empty_string = PyUnicode_FromString("");
-        if (empty_string == NULL)
-            return -1;
-        PyUnicode_InternInPlace(&empty_string);
-    }
     return 0;
 }
 
@@ -297,7 +289,7 @@ traceback_to_tuple(traceback_t* tb)
     PyObject* stack = PyTuple_New(tb->nframe);
 
     for (uint16_t nframe = 0; nframe < tb->nframe; nframe++) {
-        PyObject* frame_tuple = PyTuple_New(4);
+        PyObject* frame_tuple = PyTuple_New(3);
 
         frame_t* frame = &tb->frames[nframe];
 
@@ -306,9 +298,6 @@ traceback_to_tuple(traceback_t* tb)
         PyTuple_SET_ITEM(frame_tuple, 1, PyLong_FromUnsignedLong(frame->lineno));
         Py_INCREF(frame->name);
         PyTuple_SET_ITEM(frame_tuple, 2, frame->name);
-        /* Class name */
-        Py_INCREF(empty_string);
-        PyTuple_SET_ITEM(frame_tuple, 3, empty_string);
 
         // Try to set the class.  If we cannot (e.g., if the sofile is reloaded
         // without module initialization), then this will result in an error if

ddtrace/profiling/collector/_traceback.pyx

@@ -8,31 +8,6 @@ from ddtrace.profiling.event import DDFrame
 log = get_logger(__name__)
 
 
-cpdef _extract_class_name(frame):
-    # type: (...) -> str
-    """Extract class name from a frame, if possible.
-
-    :param frame: The frame object.
-    """
-    code = frame.f_code
-    if code.co_argcount > 0:
-        # Retrieve the name of the first argument, if the code object has any
-        argname = code.co_varnames[0]
-        try:
-            value = frame.f_locals[argname]
-        except Exception:
-            log.debug("Unable to extract class name from frame %r", frame, exc_info=True)
-            return ""
-        try:
-            if argname == "self":
-                return object.__getattribute__(type(value), "__name__")  # use type() and object.__getattribute__ to avoid side-effects
-            if argname == "cls":
-                return object.__getattribute__(value, "__name__")
-        except AttributeError:
-            return ""
-    return ""
-
-
 cpdef traceback_to_frames(traceback, max_nframes):
     """Serialize a Python traceback object into a list of tuple of (filename, lineno, function_name).
 
@@ -48,7 +23,7 @@ cpdef traceback_to_frames(traceback, max_nframes):
             frame = tb.tb_frame
             code = frame.f_code
             lineno = 0 if frame.f_lineno is None else frame.f_lineno
-            frames.insert(0, DDFrame(code.co_filename, lineno, code.co_name, _extract_class_name(frame)))
+            frames.insert(0, DDFrame(code.co_filename, lineno, code.co_name))
         nframes += 1
         tb = tb.tb_next
     return frames, nframes
@@ -92,7 +67,7 @@ cpdef pyframe_to_frames(frame, max_nframes):
                     return [], 0
 
             lineno = 0 if frame.f_lineno is None else frame.f_lineno
-            frames.append(DDFrame(code.co_filename, lineno, code.co_name, _extract_class_name(frame)))
+            frames.append(DDFrame(code.co_filename, lineno, code.co_name))
         nframes += 1
         frame = frame.f_back
     return frames, nframes

ddtrace/profiling/collector/stack.pyx

@@ -317,7 +317,6 @@ cdef stack_collect(ignore_profiler, thread_time, max_nframes, interval, wall_tim
                 handle.push_threadinfo(thread_id, thread_native_id, thread_name)
                 handle.push_task_id(task_id)
                 handle.push_task_name(task_name)
-                handle.push_class_name(frames[0].class_name)
                 for frame in frames:
                     handle.push_frame(frame.function_name, frame.file_name, 0, frame.lineno)
                 handle.flush_sample()
@@ -330,7 +329,6 @@ cdef stack_collect(ignore_profiler, thread_time, max_nframes, interval, wall_tim
             handle.push_cputime( cpu_time, 1)
             handle.push_walltime( wall_time, 1)
             handle.push_threadinfo(thread_id, thread_native_id, thread_name)
-            handle.push_class_name(frames[0].class_name)
             for frame in frames:
                 handle.push_frame(frame.function_name, frame.file_name, 0, frame.lineno)
             handle.push_span(span)
@@ -346,7 +344,6 @@ cdef stack_collect(ignore_profiler, thread_time, max_nframes, interval, wall_tim
                 handle.push_monotonic_ns(now_ns)
                 handle.push_threadinfo(thread_id, thread_native_id, thread_name)
                 handle.push_exceptioninfo(exc_type, 1)
-                handle.push_class_name(frames[0].class_name)
                 for frame in frames:
                     handle.push_frame(frame.function_name, frame.file_name, 0, frame.lineno)
                 handle.push_span(span)

ddtrace/profiling/event.py

@@ -2,5 +2,5 @@
 import typing
 
 
-DDFrame = namedtuple("DDFrame", ["file_name", "lineno", "function_name", "class_name"])
+DDFrame = namedtuple("DDFrame", ["file_name", "lineno", "function_name"])
 StackTraceType = typing.List[DDFrame]

releasenotes/notes/profiling-f_locals-c345ca501ca9b74f.yaml

@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    profiling: Fixes a segmentation fault caused by accessing ``frame.f_locals``
+    while trying to retrieve class name of a ``PyFrameObject``.

tests/profiling/collector/test_memalloc.py

@@ -90,11 +90,10 @@ def test_iter_events():
             __file__,
             _ALLOC_LINE_NUMBER,
             "<listcomp>" if sys.version_info < (3, 12) else "_allocate_1k",
-            "",
         ):
             assert thread_id == threading.main_thread().ident
             if sys.version_info < (3, 12) and len(stack) > 1:
-                assert stack[1] == DDFrame(__file__, _ALLOC_LINE_NUMBER, "_allocate_1k", "")
+                assert stack[1] == DDFrame(__file__, _ALLOC_LINE_NUMBER, "_allocate_1k")
             object_count += sample.count
 
     assert object_count >= 1000
@@ -156,12 +155,11 @@ def test_iter_events_multi_thread():
             __file__,
             _ALLOC_LINE_NUMBER,
             "<listcomp>" if sys.version_info < (3, 12) else "_allocate_1k",
-            "",
         ):
             if thread_id == threading.main_thread().ident:
                 count_object += sample.count
                 if sys.version_info < (3, 12) and len(stack) > 1:
-                    assert stack[1] == DDFrame(__file__, _ALLOC_LINE_NUMBER, "_allocate_1k", "")
+                    assert stack[1] == DDFrame(__file__, _ALLOC_LINE_NUMBER, "_allocate_1k")
             elif thread_id == t.ident:
                 count_thread += sample.count
                 entry = 2 if sys.version_info < (3, 12) else 1
@@ -205,7 +203,6 @@ def _test_heap_impl(collector, max_nframe):
             __file__,
             _ALLOC_LINE_NUMBER,
             "<listcomp>" if sys.version_info < (3, 12) else "_allocate_1k",
-            "",
         ):
             break
     else:
@@ -229,7 +226,6 @@ def _test_heap_impl(collector, max_nframe):
             __file__,
             _ALLOC_LINE_NUMBER,
             "<listcomp>" if sys.version_info < (3, 12) else "_allocate_1k",
-            "",
         ):
             break
     else:
@@ -258,7 +254,6 @@ def _test_heap_impl(collector, max_nframe):
                 __file__,
                 _ALLOC_LINE_NUMBER,
                 "<listcomp>" if sys.version_info < (3, 12) else "_allocate_1k",
-                "",
             )
             and stack[entry].function_name == "_test_heap_impl"
         ):

tests/profiling/collector/test_stack.py

@@ -114,11 +114,9 @@ def _find_sleep_event(events, class_name):
 
     for e in events:
         for frame in e.frames:
-            if frame[0] == __file__.replace(".pyc", ".py") and frame[2] == "sleep_class" and frame[3] == class_name:
+            if frame[0] == __file__.replace(".pyc", ".py") and frame[2] == "sleep_class":
                 class_method_found = True
-            elif (
-                frame[0] == __file__.replace(".pyc", ".py") and frame[2] == "sleep_instance" and frame[3] == class_name
-            ):
+            elif frame[0] == __file__.replace(".pyc", ".py") and frame[2] == "sleep_instance":
                 class_classmethod_found = True
 
         if class_method_found and class_classmethod_found:

tests/profiling/collector/test_traceback.py

@@ -17,6 +17,6 @@ def test_check_traceback_to_frames():
 
     this_file = __file__.replace(".pyc", ".py")
     assert frames == [
-        (this_file, 7, "_x", ""),
-        (this_file, 15, "test_check_traceback_to_frames", ""),
+        (this_file, 7, "_x"),
+        (this_file, 15, "test_check_traceback_to_frames"),
     ]