fix(profiling): remove unnecessary access to frame.f_locals

ddtrace/profiling/collector/_memalloc_tb.cpp

@@ -9,8 +9,6 @@
 /* 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;
 
 static PyObject* ddframe_class = NULL;
 
@@ -54,13 +52,6 @@ traceback_t::init()
             return false;
         PyUnicode_InternInPlace(&unknown_name);
     }
-
-    if (empty_string == NULL) {
-        empty_string = PyUnicode_FromString("");
-        if (empty_string == NULL)
-            return false;
-        PyUnicode_InternInPlace(&empty_string);
-    }
     return true;
 }
 
@@ -183,7 +174,7 @@ traceback_t::to_tuple() const
     PyObject* stack = PyTuple_New(frames.size());
 
     for (size_t nframe = 0; nframe < frames.size(); nframe++) {
-        PyObject* frame_tuple = PyTuple_New(4);
+        PyObject* frame_tuple = PyTuple_New(3);
 
         const frame_t& frame = frames[nframe];
 
@@ -192,9 +183,6 @@ traceback_t::to_tuple() const
         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 pyframe_to_frames(frame, max_nframes):
     """Convert a Python frame to a list of frames.
 
@@ -71,7 +46,7 @@ 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/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``.