bpo-45256: Avoid C calls for most Python to Python calls. (GH-28937)

* Avoid making C calls for most calls to Python functions.

* Change initialize_locals(steal=true) and _PyTuple_FromArraySteal to consume the argument references regardless of whether they succeed or fail.

Lib/test/test_gdb.py

@@ -724,24 +724,36 @@ def test_two_abs_args(self):
                            '   3    def foo(a, b, c):\n',
                            bt)
 
+SAMPLE_WITH_C_CALL = """
+
+from _testcapi import pyobject_fastcall
+
+def foo(a, b, c):
+    bar(a, b, c)
+
+def bar(a, b, c):
+    pyobject_fastcall(baz, (a, b, c))
+
+def baz(*args):
+    id(42)
+
+foo(1, 2, 3)
+
+"""
+
+
 class StackNavigationTests(DebuggerTests):
     @unittest.skipUnless(HAS_PYUP_PYDOWN, "test requires py-up/py-down commands")
     @unittest.skipIf(python_is_optimized(),
                      "Python was compiled with optimizations")
     def test_pyup_command(self):
         'Verify that the "py-up" command works'
-        bt = self.get_stack_trace(script=self.get_sample_script(),
+        bt = self.get_stack_trace(source=SAMPLE_WITH_C_CALL,
                                   cmds_after_breakpoint=['py-up', 'py-up'])
         self.assertMultilineMatches(bt,
                                     r'''^.*
-#[0-9]+ Frame 0x-?[0-9a-f]+, for file .*gdb_sample.py, line 10, in baz \(args=\(1, 2, 3\)\)
-    id\(42\)
-#[0-9]+ Frame 0x-?[0-9a-f]+, for file .*gdb_sample.py, line 7, in bar \(a=1, b=2, c=3\)
-    baz\(a, b, c\)
-#[0-9]+ Frame 0x-?[0-9a-f]+, for file .*gdb_sample.py, line 4, in foo \(a=1, b=2, c=3\)
-    bar\(a=a, b=b, c=c\)
-#[0-9]+ Frame 0x-?[0-9a-f]+, for file .*gdb_sample.py, line 12, in <module> \(\)
-    foo\(1, 2, 3\)
+#[0-9]+ Frame 0x-?[0-9a-f]+, for file <string>, line 12, in baz \(args=\(1, 2, 3\)\)
+#[0-9]+ <built-in method pyobject_fastcall of module object at remote 0x[0-9a-f]+>
 $''')
 
     @unittest.skipUnless(HAS_PYUP_PYDOWN, "test requires py-up/py-down commands")
@@ -765,22 +777,13 @@ def test_up_at_top(self):
                      "Python was compiled with optimizations")
     def test_up_then_down(self):
         'Verify "py-up" followed by "py-down"'
-        bt = self.get_stack_trace(script=self.get_sample_script(),
+        bt = self.get_stack_trace(source=SAMPLE_WITH_C_CALL,
                                   cmds_after_breakpoint=['py-up', 'py-up', 'py-down'])
         self.assertMultilineMatches(bt,
                                     r'''^.*
-#[0-9]+ Frame 0x-?[0-9a-f]+, for file .*gdb_sample.py, line 10, in baz \(args=\(1, 2, 3\)\)
-    id\(42\)
-#[0-9]+ Frame 0x-?[0-9a-f]+, for file .*gdb_sample.py, line 7, in bar \(a=1, b=2, c=3\)
-    baz\(a, b, c\)
-#[0-9]+ Frame 0x-?[0-9a-f]+, for file .*gdb_sample.py, line 4, in foo \(a=1, b=2, c=3\)
-    bar\(a=a, b=b, c=c\)
-#[0-9]+ Frame 0x-?[0-9a-f]+, for file .*gdb_sample.py, line 12, in <module> \(\)
-    foo\(1, 2, 3\)
-#[0-9]+ Frame 0x-?[0-9a-f]+, for file .*gdb_sample.py, line 10, in baz \(args=\(1, 2, 3\)\)
-    id\(42\)
-#[0-9]+ Frame 0x-?[0-9a-f]+, for file .*gdb_sample.py, line 7, in bar \(a=1, b=2, c=3\)
-    baz\(a, b, c\)
+#[0-9]+ Frame 0x-?[0-9a-f]+, for file <string>, line 12, in baz \(args=\(1, 2, 3\)\)
+#[0-9]+ <built-in method pyobject_fastcall of module object at remote 0x[0-9a-f]+>
+#[0-9]+ Frame 0x-?[0-9a-f]+, for file <string>, line 12, in baz \(args=\(1, 2, 3\)\)
 $''')
 
 class PyBtTests(DebuggerTests):
@@ -970,13 +973,12 @@ def __init__(self):
         self.assertRegex(gdb_output,
                          r"<method-wrapper u?'__init__' of MyList object at ")
 
-
 class PyPrintTests(DebuggerTests):
     @unittest.skipIf(python_is_optimized(),
                      "Python was compiled with optimizations")
     def test_basic_command(self):
         'Verify that the "py-print" command works'
-        bt = self.get_stack_trace(script=self.get_sample_script(),
+        bt = self.get_stack_trace(source=SAMPLE_WITH_C_CALL,
                                   cmds_after_breakpoint=['py-up', 'py-print args'])
         self.assertMultilineMatches(bt,
                                     r".*\nlocal 'args' = \(1, 2, 3\)\n.*")
@@ -985,7 +987,7 @@ def test_basic_command(self):
                      "Python was compiled with optimizations")
     @unittest.skipUnless(HAS_PYUP_PYDOWN, "test requires py-up/py-down commands")
     def test_print_after_up(self):
-        bt = self.get_stack_trace(script=self.get_sample_script(),
+        bt = self.get_stack_trace(source=SAMPLE_WITH_C_CALL,
                                   cmds_after_breakpoint=['py-up', 'py-up', 'py-print c', 'py-print b', 'py-print a'])
         self.assertMultilineMatches(bt,
                                     r".*\nlocal 'c' = 3\nlocal 'b' = 2\nlocal 'a' = 1\n.*")

Objects/tupleobject.c

@@ -490,9 +490,11 @@ _PyTuple_FromArraySteal(PyObject *const *src, Py_ssize_t n)
     if (n == 0) {
         return tuple_get_empty();
     }
-
     PyTupleObject *tuple = tuple_alloc(n);
     if (tuple == NULL) {
+        for (Py_ssize_t i = 0; i < n; i++) {
+            Py_DECREF(src[i]);
+        }
         return NULL;
     }
     PyObject **dst = tuple->ob_item;