bpo-41798: Allocate _decimal extension module C API on the heap (GH-24117)

Author: Erlend Egeberg Aasland

Include/pydecimal.h

@@ -66,6 +66,8 @@ typedef struct {
 /*                                Capsule API                               */
 /****************************************************************************/
 
+#define PyDec_CAPSULE_NAME "_decimal._API"
+
 /* Simple API */
 #define PyDec_TypeCheck_INDEX 0
 #define PyDec_TypeCheck_RETURN int
@@ -164,7 +166,7 @@ static void **_decimal_api;
 static int
 import_decimal(void)
 {
-    _decimal_api = (void **)PyCapsule_Import("_decimal._API", 0);
+    _decimal_api = (void **)PyCapsule_Import(PyDec_CAPSULE_NAME, 0);
     if (_decimal_api == NULL) {
         return -1;
     }

Modules/_decimal/_decimal.c

@@ -5574,8 +5574,6 @@ static PyTypeObject PyDecContext_Type =
 /*                                   C-API                                  */
 /****************************************************************************/
 
-static void *_decimal_api[CPYTHON_DECIMAL_MAX_API];
-
 /* Simple API */
 static int
 PyDec_TypeCheck(const PyObject *v)
@@ -5699,9 +5697,22 @@ PyDec_GetConst(const PyObject *v)
     return MPD(v);
 }
 
+static void
+destroy_api(PyObject *capsule)
+{
+    void *capi = PyCapsule_GetPointer(capsule, PyDec_CAPSULE_NAME);
+    PyMem_Free(capi);
+}
+
 static PyObject *
 init_api(void)
 {
+    void **_decimal_api = PyMem_Calloc(CPYTHON_DECIMAL_MAX_API, sizeof(void *));
+    if (_decimal_api == NULL) {
+        PyErr_NoMemory();
+        return NULL;
+    }
+
     /* Simple API */
     _decimal_api[PyDec_TypeCheck_INDEX] = (void *)PyDec_TypeCheck;
     _decimal_api[PyDec_IsSpecial_INDEX] = (void *)PyDec_IsSpecial;
@@ -5716,7 +5727,11 @@ init_api(void)
     _decimal_api[PyDec_Get_INDEX] = (void *)PyDec_Get;
     _decimal_api[PyDec_GetConst_INDEX] = (void *)PyDec_GetConst;
 
-    return PyCapsule_New(_decimal_api, "_decimal._API", NULL);
+    PyObject *capsule = PyCapsule_New(_decimal_api, PyDec_CAPSULE_NAME, destroy_api);
+    if (!capsule) {
+        PyMem_Free(_decimal_api);
+    }
+    return capsule;
 }
 
 
@@ -6080,8 +6095,7 @@ PyInit__decimal(void)
     CHECK_INT(PyModule_AddStringConstant(m, "__libmpdec_version__", mpd_version()));
 
     /* Add capsule API */
-    Py_INCREF(capsule);
-    if (PyModule_AddObject(m, "_API", capsule) < 0) {
+    if (PyModule_AddObjectRef(m, "_API", capsule) < 0) {
         goto error;
     }
 
@@ -6107,6 +6121,7 @@ PyInit__decimal(void)
     Py_CLEAR(basic_context_template); /* GCOV_NOT_REACHED */
     Py_CLEAR(extended_context_template); /* GCOV_NOT_REACHED */
     Py_CLEAR(m); /* GCOV_NOT_REACHED */
+    Py_CLEAR(capsule); /* GCOV_NOT_REACHED */
 
     return NULL; /* GCOV_NOT_REACHED */
 }