From d65c700a2e4a9dbc625f84e6bb9bedd12e182c19 Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@redhat.com>
Date: Thu, 22 Nov 2018 02:56:20 +0100
Subject: [PATCH] bpo-35059: Add assertion to _PyObject_CAST()

_PyObject_CAST() and _PyVarObject_CAST() macros now require that the
type of the argument has a size. For example, _PyObject_CAST(frame)
now raises a compilation error if frame type is "struct _frame*" but
"struct _frame" is not defined.

_PyObject_CAST() and _PyVarObject_CAST() macros now raise a
compilation error if the argument is a "PyObject" or a "PyObject**".

Partially revert b37672daf61740fe1ff9d805f6d74bc5ef04012b to show
that _PyObject_CAST() accepts non-trivial expressions.
---
 Include/object.h        | 31 ++++++++++++++++++++++++++-----
 Modules/_ssl.c          |  9 +++------
 Objects/weakrefobject.c |  3 +--
 Python/pystate.c        |  1 +
 4 files changed, 31 insertions(+), 13 deletions(-)

diff --git a/Include/object.h b/Include/object.h
index cdcdca85c633a1b..9d3a367ec7d9fd9 100644
--- a/Include/object.h
+++ b/Include/object.h
@@ -112,16 +112,37 @@ typedef struct _object {
     struct _typeobject *ob_type;
 } PyObject;
 
-/* Cast argument to PyObject* type. */
-#define _PyObject_CAST(op) ((PyObject*)(op))
-
 typedef struct {
     PyObject ob_base;
     Py_ssize_t ob_size; /* Number of items in variable part */
 } PyVarObject;
 
-/* Cast argument to PyVarObject* type. */
-#define _PyVarObject_CAST(op) ((PyVarObject*)(op))
+/* sizeof(*op) doesn't work on Visual Studio with void*:
+   sizeof(void) raises a compilation error.
+
+   sizeof(*op) is incompatible with Py_LIMITED_API which doesn't define
+   structures. */
+#if !defined(_MSC_VER) && !defined(Py_LIMITED_API)
+/* _PyObject_CAST(op): Cast argument to PyObject* type.
+
+   Raise a compilation error if the argument type is PyObject or PyObject**.
+
+   Detect for example the bug "&item" instead of "item" in:
+
+   const char *func(PyObject *item) { return Py_TYPE(&item)->tp_name; }
+
+   Note: sizeof(op) doesn't evaluate 'op', so sizeof(op) has no side effect. */
+#  define _PyObject_CAST(op) \
+    ((PyObject*)(op) + Py_BUILD_ASSERT_EXPR(sizeof(*(op)) != sizeof(op)))
+
+/* _PyVarObject_CAST(op): Cast argument to PyVarObject* type.
+   Similar to _PyObject_CAST(). */
+#  define _PyVarObject_CAST(op) \
+    ((PyVarObject*)(op) + Py_BUILD_ASSERT_EXPR(sizeof(*(op)) != sizeof(op)))
+#else
+#  define _PyObject_CAST(op) ((PyObject*)(op))
+#  define _PyVarObject_CAST(op) ((PyVarObject*)(op))
+#endif   /* defined(_MSC_VER) */
 
 #define Py_REFCNT(ob)           (_PyObject_CAST(ob)->ob_refcnt)
 #define Py_TYPE(ob)             (_PyObject_CAST(ob)->ob_type)
diff --git a/Modules/_ssl.c b/Modules/_ssl.c
index 85819f5b0509029..93498f475609d06 100644
--- a/Modules/_ssl.c
+++ b/Modules/_ssl.c
@@ -5983,12 +5983,9 @@ PyInit__ssl(void)
     PyModule_AddIntConstant(m, "PROTO_TLSv1_2", PY_PROTO_TLSv1_2);
     PyModule_AddIntConstant(m, "PROTO_TLSv1_3", PY_PROTO_TLSv1_3);
 
-#define addbool(m, key, value) \
-    do { \
-        PyObject *bool_obj = (value) ? Py_True : Py_False; \
-        Py_INCREF(bool_obj); \
-        PyModule_AddObject((m), (key), bool_obj); \
-    } while (0)
+#define addbool(m, v, b) \
+    Py_INCREF((b) ? Py_True : Py_False); \
+    PyModule_AddObject((m), (v), (b) ? Py_True : Py_False);
 
 #if HAVE_SNI
     addbool(m, "HAS_SNI", 1);
diff --git a/Objects/weakrefobject.c b/Objects/weakrefobject.c
index 9227aa688f47e1d..9f492e4b25e49fa 100644
--- a/Objects/weakrefobject.c
+++ b/Objects/weakrefobject.c
@@ -833,8 +833,7 @@ PyWeakref_NewProxy(PyObject *ob, PyObject *callback)
                        to avoid violating the invariants of the list
                        of weakrefs for ob. */
                     Py_DECREF(result);
-                    result = proxy;
-                    Py_INCREF(result);
+                    Py_INCREF(result = proxy);
                     goto skip_insert;
                 }
                 prev = ref;
diff --git a/Python/pystate.c b/Python/pystate.c
index f86f5a96f07450d..e7b9363d565b0da 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -2,6 +2,7 @@
 /* Thread and interpreter state structures and their interfaces */
 
 #include "Python.h"
+#include "frameobject.h"
 #include "pycore_pymem.h"
 #include "pycore_pystate.h"