Backporting METH_FASTCALL from Python 3.7 (#317)

* dict copy speedup

refer to bpo-31179 or python/cpython@boa7a037b8fde

* __build_class__() uses METH_FASTCALL

refer python/cpython@69de71b255
refer python/cpython@773dc6dd06

a single test related to __prepare__ fails.

* type_prepare uses METH_FASTCALL

refer python/cpython@d526cfe546
refer python/cpython@80ab22fa2c

the prepare-related test still fails.  It's just related to the error
message format though.

* separate into ParseStack and ParseStackAndKeywords

refer python/cpython@6518a93cb1
refer python/cpython@3e1fad6913
refer python/cpython@c0083fc47d

* Add _PyArg_NoStackKeywords

refer python/cpython@29d39cc8f5

* _PyStack_UnpackDict now returns int

refer python/cpython@998c20962c

* METH_FASTCALL changes to .inc files

done via python's Argument Clinic tool,
refer python/cpython@259f0e4437

* Added _PyArg_UnpackStack

refer python/cpython@fe54dda08

* Argument Clinic FASTCALL again

refer python/cpython@0c4a828ca

* Argument Clinic for ordered dictionary object

refer python/cpython@b05cbac052

* speed up getargs

refer python/cpython@1741441649

* FASTCALL for sorted, next, and getattr

refer python/cpython@5a60ecaa7a
refer python/cpython@fda6d0acf0
refer python/cpython@84b388bb80

* Optimize methoddescr_call

refer python/cpython@2a1b676d1f
refer python/cpython@c52572319c
refer python/cpython@35ecebe165
refer python/cpython@8128d5a491

* cleanup _PyMethodDef_RawFastCallDict

refer python/cpython@0a2e46835d
refer python/cpython@98ccba8344
refer python/cpython@c89ef828cf
refer python/cpython@250e4b0063

* print now uses METH_FASTCALL

refer python/cpython@c3858bd7c6
refer python/cpython@bd584f169f
refer python/cpython@06d34393c2

* _struct module now uses Argument Clinic

refer python/cpython@3f2d10132d

* make deque methods faster

refer python/cpython@dd407d5006

* recursive calls in PyObject_Call

refer python/cpython@7399a05965

only partially ported, because RawFastCallKeywords hasn't been ported

* add macros

refer python/cpython@68a001dd59

* all tests pass in MODE=dbg

* convert some internal functions to FASTCALL

__import__ might need to be changed later, if it is possible to backport
the METH_FASTCALL | METH_KEYWORDS flag distinction later.

* speed up unpickling

refer python/cpython@bee09aecc2

* added _PyMethodDef_RawFastCallKeywords

refer python/cpython@7399a05965

* PyCFunction_Call performance

refer python/cpython@12c5838dae

* avoid PyMethodObject in slots

main change in python/cpython@516b98161a
test_exceptions changed in python/cpython@331bbe6aaa
type_settattro changed in python/cpython@193f7e094f
_PyObject_CallFunctionVa changed in python/cpython@fe4ff83049

* fix refcount error found in MODE=dbg

all tests now pass in MODE=dbg

third_party/python/Lib/test/test_dict.py

@@ -272,11 +272,57 @@ class DictTest(unittest.TestCase):
         self.assertEqual(baddict3.fromkeys({"a", "b", "c"}), res)
 
     def test_copy(self):
-        d = {1:1, 2:2, 3:3}
-        self.assertEqual(d.copy(), {1:1, 2:2, 3:3})
+        d = {1: 1, 2: 2, 3: 3}
+        self.assertIsNot(d.copy(), d)
+        self.assertEqual(d.copy(), d)
+        self.assertEqual(d.copy(), {1: 1, 2: 2, 3: 3})
+
+        copy = d.copy()
+        d[4] = 4
+        self.assertNotEqual(copy, d)
+
         self.assertEqual({}.copy(), {})
         self.assertRaises(TypeError, d.copy, None)
 
+    def test_copy_fuzz(self):
+        for dict_size in [10, 100, 1000, 10000, 100000]:
+            dict_size = random.randrange(
+                dict_size // 2, dict_size + dict_size // 2)
+            with self.subTest(dict_size=dict_size):
+                d = {}
+                for i in range(dict_size):
+                    d[i] = i
+
+                d2 = d.copy()
+                self.assertIsNot(d2, d)
+                self.assertEqual(d, d2)
+                d2['key'] = 'value'
+                self.assertNotEqual(d, d2)
+                self.assertEqual(len(d2), len(d) + 1)
+
+    def test_copy_maintains_tracking(self):
+        class A:
+            pass
+
+        key = A()
+
+        for d in ({}, {'a': 1}, {key: 'val'}):
+            d2 = d.copy()
+            self.assertEqual(gc.is_tracked(d), gc.is_tracked(d2))
+
+    def test_copy_noncompact(self):
+        # Dicts don't compact themselves on del/pop operations.
+        # Copy will use a slow merging strategy that produces
+        # a compacted copy when roughly 33% of dict is a non-used
+        # keys-space (to optimize memory footprint).
+        # In this test we want to hit the slow/compacting
+        # branch of dict.copy() and make sure it works OK.
+        d = {k: k for k in range(1000)}
+        for k in range(950):
+            del d[k]
+        d2 = d.copy()
+        self.assertEqual(d2, d)
+
     def test_get(self):
         d = {}
         self.assertIs(d.get('c'), None)

third_party/python/Lib/test/test_exceptions.py

@@ -1162,27 +1162,20 @@ class ExceptionTests(unittest.TestCase):
                 # The following line is included in the traceback report:
                 raise exc
 
-        class BrokenRepr(BrokenDel):
-            def __repr__(self):
-                raise AttributeError("repr() is broken")
-
         class BrokenExceptionDel:
             def __del__(self):
                 exc = BrokenStrException()
                 # The following line is included in the traceback report:
                 raise exc
 
-        for test_class in (BrokenDel, BrokenRepr, BrokenExceptionDel):
+        for test_class in (BrokenDel, BrokenExceptionDel):
             with self.subTest(test_class):
                 obj = test_class()
                 with captured_stderr() as stderr:
                     del obj
                 report = stderr.getvalue()
                 self.assertIn("Exception ignored", report)
-                if test_class is BrokenRepr:
-                    self.assertIn("<object repr() failed>", report)
-                else:
-                    self.assertIn(test_class.__del__.__qualname__, report)
+                self.assertIn(test_class.__del__.__qualname__, report)
                 self.assertIn("test_exceptions.py", report)
                 self.assertIn("raise exc", report)
                 if test_class is BrokenExceptionDel: