Backport of r66677: _lsprof crasher when a bad external timer is used during

garbage collection of a Profiler object.

Lib/test/test_cProfile.py

 """Test suite for the cProfile module."""
-
-import cProfile, pstats, sys
+import cProfile, pstats, sys, test.test_support
 
 # In order to have reproducible time, we simulate a timer in the global
 # variable 'ticks', which represents simulated time in milliseconds.
@@ -23,6 +22,7 @@ def test_main():
     st.strip_dirs().sort_stats('stdname').print_stats()
     st.print_callees()
     st.print_callers()
+    test_bad_counter_during_dealloc()
 
 def timer():
     return ticks
@@ -119,5 +119,20 @@ class C:
         ticks += 1
         raise AttributeError
 
+# Issue 3895.
+def test_bad_counter_during_dealloc():
+    import _lsprof
+    # Must use a file as StringIO doesn't trigger the bug.
+    sys.stderr = open(test.test_support.TESTFN, 'w')
+    try:
+        obj = _lsprof.Profiler(lambda: int)
+        obj.enable()
+        obj = _lsprof.Profiler(1)
+        obj.disable()
+    finally:
+        sys.stderr = sys.__stderr__
+        test.test_support.unlink(test.test_support.TESTFN)
+
+
 if __name__ == "__main__":
     test_main()

Misc/NEWS

@@ -92,6 +92,9 @@ Core and builtins
 Library
 -------
 
+- Issue #3895: _lsprof could be crashed with an external timer that did not
+  return a float when a Profiler object is garbage collected.
+
 - Issues #3968 and #3969: two minor turtle problems.
 
 - Issue #3547: Fixed ctypes structures bitfields of varying integer

Modules/_lsprof.c

@@ -150,7 +150,16 @@ static PY_LONG_LONG CallExternalTimer(ProfilerObject *pObj)
 	}
 	Py_DECREF(o);
 	if (PyErr_Occurred()) {
-		PyErr_WriteUnraisable((PyObject *) pObj);
+		PyObject *context = (PyObject *)pObj;
+		/* May have been called by profiler_dealloc(). */
+		if (context->ob_refcnt < 1) {
+			context = PyString_FromString("profiler calling an "
+							"external timer");
+			if (context == NULL) {
+				return 0;
+			}
+		}
+		PyErr_WriteUnraisable(context);
 		return 0;
 	}
 	return result;