Suppress uninitialized variable warnings for small stack allocations

Add macros to disable and re-enable compiler-specific warnings about
possibly uninitialized variables (`-Wmaybe-uninitialized` for GCC,
`-Wuninitialized` for Clang, and warning C4700 for MSVC). Use these
macros in `_PyEvalFramePushAndInit_Ex()` to suppress false positives
on stack-allocated arrays like `stack_array`.

This also addresses warnings such as the one in `pycore_call.h` when
using `small_stack[_PY_FASTCALL_SMALL_STACK]` that may be flagged by
GCC's `-Wmaybe-uninitialized`.

Author: dura0ok

Include/pymacro.h

@@ -199,4 +199,21 @@ PyAPI_FUNC(uint32_t) Py_PACK_VERSION(int x, int y);
 #endif // Py_LIMITED_API < 3.14
 
 
+#if defined(__clang__)
+    #define DISABLE_UNINIT_WARNINGS _Pragma("clang diagnostic push") \
+                                     _Pragma("clang diagnostic ignored \"-Wuninitialized\"")
+    #define ENABLE_UNINIT_WARNINGS  _Pragma("clang diagnostic pop")
+#elif defined(__GNUC__) || defined(__GNUG__)
+    #define DISABLE_UNINIT_WARNINGS _Pragma("GCC diagnostic push") \
+                                     _Pragma("GCC diagnostic ignored \"-Wmaybe-uninitialized\"")
+    #define ENABLE_UNINIT_WARNINGS  _Pragma("GCC diagnostic pop")
+#elif defined(_MSC_VER)
+    #define DISABLE_UNINIT_WARNINGS __pragma(warning(push)) \
+                                     __pragma(warning(disable: 4700))
+    #define ENABLE_UNINIT_WARNINGS  __pragma(warning(pop))
+#else
+    #define DISABLE_UNINIT_WARNINGS
+    #define ENABLE_UNINIT_WARNINGS
+#endif
+
 #endif /* Py_PYMACRO_H */

Python/ceval.c

@@ -1814,6 +1814,7 @@ _PyEvalFramePushAndInit_Ex(PyThreadState *tstate, _PyStackRef func,
     PyObject *kwnames = NULL;
     _PyStackRef *newargs;
     PyObject *const *object_array = NULL;
+    DISABLE_UNINIT_WARNINGS
     _PyStackRef stack_array[8];
     if (has_dict) {
         object_array = _PyStack_UnpackDict(tstate, _PyTuple_ITEMS(callargs), nargs, kwargs, &kwnames);
@@ -1855,6 +1856,7 @@ _PyEvalFramePushAndInit_Ex(PyThreadState *tstate, _PyStackRef func,
     else if (nargs > 8) {
        PyMem_Free((void *)newargs);
     }
+    ENABLE_UNINIT_WARNINGS
     /* No need to decref func here because the reference has been stolen by
        _PyEvalFramePushAndInit.
     */