Fix build failing from undefined behavior of implicit casting structs.

Author: gresm

src_c/include/pygame_mixer.h

@@ -50,7 +50,7 @@ typedef struct {
 PYGAMEAPI_DEFINE_SLOTS(mixer);
 
 #define pgSound_Type (*(PyTypeObject *)PYGAMEAPI_GET_SLOT(mixer, 0))
-#define pgSound_Check(x) (PyObject_IsInstance(x, &pgSound_Type))
+#define pgSound_Check(x) (PyObject_IsInstance(x, (PyObject *)&pgSound_Type))
 
 #define pgSound_New \
     (*(PyObject * (*)(Mix_Chunk *)) PYGAMEAPI_GET_SLOT(mixer, 1))
@@ -59,7 +59,8 @@ PYGAMEAPI_DEFINE_SLOTS(mixer);
     (*(PyObject * (*)(PyObject *, PyObject *)) PYGAMEAPI_GET_SLOT(mixer, 2))
 
 #define pgChannel_Type (*(PyTypeObject *)PYGAMEAPI_GET_SLOT(mixer, 3))
-#define pgChannel_Check(x) (PyObject_IsInstance(x, &pgChannel_Type))
+#define pgChannel_Check(x) \
+    (PyObject_IsInstance(x, (PyObject *)&pgChannel_Type))
 
 #define pgChannel_New (*(PyObject * (*)(int)) PYGAMEAPI_GET_SLOT(mixer, 4))
 

src_c/mixer.c

@@ -85,8 +85,9 @@ static PyObject *
 pgSound_New(Mix_Chunk *);
 static PyObject *
 pgChannel_New(int);
-#define pgSound_Check(x) (PyObject_IsInstance(x, &pgSound_Type))
-#define pgChannel_Check(x) (PyObject_IsInstance(x, &pgChannel_Type))
+#define pgSound_Check(x) (PyObject_IsInstance(x, (PyObject *)&pgSound_Type))
+#define pgChannel_Check(x) \
+    (PyObject_IsInstance(x, (PyObject *)&pgChannel_Type))
 
 static int
 snd_getbuffer(PyObject *, Py_buffer *, int);