gh-119333: Add c-api to have contextvar enter/exit callbacks

Include/cpython/context.h

@@ -27,14 +27,9 @@ PyAPI_FUNC(PyObject *) PyContext_CopyCurrent(void);
 PyAPI_FUNC(int) PyContext_Enter(PyObject *);
 PyAPI_FUNC(int) PyContext_Exit(PyObject *);
 
-#define Py_FOREACH_CONTEXT_EVENT(V) \
-   V(ENTER)                      \
-   V(EXIT)
-
 typedef enum {
-   #define Py_DEF_EVENT(op) Py_CONTEXT_EVENT_##op,
-   Py_FOREACH_CONTEXT_EVENT(Py_DEF_EVENT)
-   #undef Py_DEF_EVENT
+   Py_CONTEXT_EVENT_ENTER,
+   Py_CONTEXT_EVENT_EXIT,
 } PyContextEvent;
 
 /*

Python/context.c

@@ -102,11 +102,10 @@ PyContext_CopyCurrent(void)
 static const char *
 context_event_name(PyContextEvent event) {
     switch (event) {
-        #define CASE(op)                   \
-        case Py_CONTEXT_EVENT_##op:         \
-            return "Py_CONTEXT_EVENT_" #op;
-        Py_FOREACH_CONTEXT_EVENT(CASE)
-        #undef CASE
+        case Py_CONTEXT_EVENT_ENTER:
+            return "Py_CONTEXT_EVENT_ENTER";
+        case Py_CONTEXT_EVENT_EXIT:
+            return "Py_CONTEXT_EVENT_EXIT";
     }
     Py_UNREACHABLE();
 }