gh-87175: Port curses capi pointer array to a struct.

Doc/whatsnew/3.10.rst

@@ -815,6 +815,11 @@ Porting to Python 3.10
   bugs like ``if (PyList_SET_ITEM (a, b, c) < 0) ...`` test.
   (Contributed by Zackery Spytz and Victor Stinner in :issue:`30459`.)
 
+* Convert the ``PyCurses_API`` C API (``_curses._C_API`` capsule) from
+  a pointer array to a structure and remove the ``PyCurses_API_pointers``
+  macro.
+  (Contributed by Hai Shi in :issue:`43009`.)
+
 Deprecated
 ----------
 

Include/py_curses.h

@@ -54,8 +54,6 @@
 extern "C" {
 #endif
 
-#define PyCurses_API_pointers 4
-
 /* Type declarations */
 
 typedef struct {
@@ -64,6 +62,13 @@ typedef struct {
     char *encoding;
 } PyCursesWindowObject;
 
+typedef struct {
+    PyTypeObject *window_type;
+    int (*setup_term_called)(void);
+    int (*initialized)(void);
+    int (*initialized_color)(void);
+} PyCurses_CAPI;
+
 #define PyCursesWindow_Check(v) Py_IS_TYPE(v, &PyCursesWindow_Type)
 
 #define PyCurses_CAPSULE_NAME "_curses._C_API"
@@ -75,15 +80,15 @@ typedef struct {
 #else
 /* This section is used in modules that use the _cursesmodule API */
 
-static void **PyCurses_API;
+static PyCurses_CAPI *PyCurses_API;
 
-#define PyCursesWindow_Type (*(PyTypeObject *) PyCurses_API[0])
-#define PyCursesSetupTermCalled  {if (! ((int (*)(void))PyCurses_API[1]) () ) return NULL;}
-#define PyCursesInitialised      {if (! ((int (*)(void))PyCurses_API[2]) () ) return NULL;}
-#define PyCursesInitialisedColor {if (! ((int (*)(void))PyCurses_API[3]) () ) return NULL;}
+#define PyCursesWindow_Type (*PyCurses_API->window_type)
+#define PyCursesSetupTermCalled  {if (!PyCurses_API->setup_term_called()) return NULL;}
+#define PyCursesInitialised      {if (!PyCurses_API->initialized()) return NULL;}
+#define PyCursesInitialisedColor {if (!PyCurses_API->initialized_color()) return NULL;}
 
 #define import_curses() \
-    PyCurses_API = (void **)PyCapsule_Import(PyCurses_CAPSULE_NAME, 1);
+    PyCurses_API = PyCapsule_Import(PyCurses_CAPSULE_NAME, 1);
 
 #endif
 

Misc/NEWS.d/next/Core and Builtins/2021-01-26-19-19-57.bpo-43009.NYkINR.rst

@@ -0,0 +1,3 @@
+Convert the ``PyCurses_API`` C API (``_curses._C_API`` capsule) from
+a pointer array to a structure and remove the ``PyCurses_API_pointers``
+macro.

Modules/_cursesmodule.c

@@ -4728,8 +4728,8 @@ static struct PyModuleDef _cursesmodule = {
 static void
 curses_destructor(PyObject *op)
 {
-    void *ptr = PyCapsule_GetPointer(op, PyCurses_CAPSULE_NAME);
-    Py_DECREF(*(void **)ptr);
+    PyCurses_CAPI *ptr = PyCapsule_GetPointer(op, PyCurses_CAPSULE_NAME);
+    Py_DECREF(ptr->window_type);
     PyMem_Free(ptr);
 }
 
@@ -4753,22 +4753,23 @@ PyInit__curses(void)
         return NULL;
     ModDict = d; /* For PyCurses_InitScr to use later */
 
-    void **PyCurses_API = PyMem_Calloc(PyCurses_API_pointers, sizeof(void *));
+    PyCurses_CAPI *PyCurses_API = PyMem_Malloc(sizeof(PyCurses_CAPI));
     if (PyCurses_API == NULL) {
         PyErr_NoMemory();
         return NULL;
     }
-    /* Initialize the C API pointer array */
-    PyCurses_API[0] = (void *)Py_NewRef(&PyCursesWindow_Type);
-    PyCurses_API[1] = (void *)func_PyCursesSetupTermCalled;
-    PyCurses_API[2] = (void *)func_PyCursesInitialised;
-    PyCurses_API[3] = (void *)func_PyCursesInitialisedColor;
+    /* Initialize the C API struct */
+    PyCurses_API->window_type = (PyTypeObject *)Py_NewRef(
+        &PyCursesWindow_Type);
+    PyCurses_API->setup_term_called = func_PyCursesSetupTermCalled;
+    PyCurses_API->initialized = func_PyCursesInitialised;
+    PyCurses_API->initialized_color = func_PyCursesInitialisedColor;
 
     /* Add a capsule for the C API */
     c_api_object = PyCapsule_New(PyCurses_API, PyCurses_CAPSULE_NAME,
                                  curses_destructor);
     if (c_api_object == NULL) {
-        Py_DECREF(PyCurses_API[0]);
+        Py_DECREF(PyCurses_API->window_type);
         PyMem_Free(PyCurses_API);
         return NULL;
     }