Fix some constness / char literal issues being found by MSVC standard conforming mode (#8344)

* Fix some constness / char literal issues being found by MSVC standard conforming mode

* Switch to const_cast from C-style casts

python/google/protobuf/pyext/descriptor_pool.cc

@@ -176,9 +176,9 @@ static PyDescriptorPool* PyDescriptorPool_NewWithDatabase(
 // The public DescriptorPool constructor.
 static PyObject* New(PyTypeObject* type,
                      PyObject* args, PyObject* kwargs) {
-  static char* kwlist[] = {"descriptor_db", 0};
+  static const char* kwlist[] = {"descriptor_db", 0};
   PyObject* py_database = NULL;
-  if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|O", kwlist, &py_database)) {
+  if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|O", const_cast<char**>(kwlist), &py_database)) {
     return NULL;
   }
   DescriptorDatabase* database = NULL;

python/google/protobuf/pyext/map_container.cc

@@ -462,10 +462,10 @@ int MapReflectionFriend::ScalarMapSetItem(PyObject* _self, PyObject* key,
 
 static PyObject* ScalarMapGet(PyObject* self, PyObject* args,
                               PyObject* kwargs) {
-  static char* kwlist[] = {"key", "default", nullptr};
+  static const char* kwlist[] = {"key", "default", nullptr};
   PyObject* key;
   PyObject* default_value = NULL;
-  if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O|O", kwlist, &key,
+  if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O|O", const_cast<char**>(kwlist), &key,
                                    &default_value)) {
     return NULL;
   }
@@ -757,10 +757,10 @@ PyObject* MapReflectionFriend::MessageMapToStr(PyObject* _self) {
 }
 
 PyObject* MessageMapGet(PyObject* self, PyObject* args, PyObject* kwargs) {
-  static char* kwlist[] = {"key", "default", nullptr};
+  static const char* kwlist[] = {"key", "default", nullptr};
   PyObject* key;
   PyObject* default_value = NULL;
-  if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O|O", kwlist, &key,
+  if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O|O", const_cast<char**>(kwlist), &key,
                                    &default_value)) {
     return NULL;
   }

python/google/protobuf/pyext/message.cc

@@ -196,12 +196,12 @@ static int AddDescriptors(PyObject* cls, const Descriptor* descriptor) {
 }
 
 static PyObject* New(PyTypeObject* type, PyObject* args, PyObject* kwargs) {
-  static char *kwlist[] = {"name", "bases", "dict", 0};
+  static const char *kwlist[] = {"name", "bases", "dict", 0};
   PyObject *bases, *dict;
   const char* name;
 
   // Check arguments: (name, bases, dict)
-  if (!PyArg_ParseTupleAndKeywords(args, kwargs, "sO!O!:type", kwlist,
+  if (!PyArg_ParseTupleAndKeywords(args, kwargs, "sO!O!:type", const_cast<char**>(kwlist),
                                    &name,
                                    &PyTuple_Type, &bases,
                                    &PyDict_Type, &dict)) {
@@ -546,7 +546,7 @@ PyObject* PickleError_class;
 
 // Format an error message for unexpected types.
 // Always return with an exception set.
-void FormatTypeError(PyObject* arg, char* expected_types) {
+void FormatTypeError(PyObject* arg, const char* expected_types) {
   // This function is often called with an exception set.
   // Clear it to call PyObject_Repr() in good conditions.
   PyErr_Clear();
@@ -1679,9 +1679,9 @@ static PyObject* InternalSerializeToString(
     CMessage* self, PyObject* args, PyObject* kwargs,
     bool require_initialized) {
   // Parse the "deterministic" kwarg; defaults to False.
-  static char* kwlist[] = { "deterministic", 0 };
+  static const char* kwlist[] = { "deterministic", 0 };
   PyObject* deterministic_obj = Py_None;
-  if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|O", kwlist,
+  if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|O", const_cast<char**>(kwlist),
                                    &deterministic_obj)) {
     return NULL;
   }

python/google/protobuf/pyext/message.h

@@ -329,7 +329,7 @@ PyObject* SetAllowOversizeProtos(PyObject* m, PyObject* arg);
 
 #define FULL_MODULE_NAME "google.protobuf.pyext._message"
 
-void FormatTypeError(PyObject* arg, char* expected_types);
+void FormatTypeError(PyObject* arg, const char* expected_types);
 template<class T>
 bool CheckAndGetInteger(PyObject* arg, T* value);
 bool CheckAndGetDouble(PyObject* arg, double* value);

python/google/protobuf/pyext/message_factory.cc

@@ -77,9 +77,9 @@ PyMessageFactory* NewMessageFactory(PyTypeObject* type, PyDescriptorPool* pool)
 }
 
 PyObject* New(PyTypeObject* type, PyObject* args, PyObject* kwargs) {
-  static char* kwlist[] = {"pool", 0};
+  static const char* kwlist[] = {"pool", 0};
   PyObject* pool = NULL;
-  if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|O", kwlist, &pool)) {
+  if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|O", const_cast<char**>(kwlist), &pool)) {
     return NULL;
   }
   ScopedPyObjectPtr owned_pool;