Issue #21233: Oops, Fix _PyObject_Alloc(): initialize nbytes before going to

redirect.

Objects/obmalloc.c

@@ -1183,12 +1183,12 @@ _PyObject_Alloc(int use_calloc, void *ctx, size_t nelem, size_t elsize)
         goto redirect;
 #endif
 
-    if (nelem == 0 || elsize == 0)
-        goto redirect;
-
     assert(nelem <= PY_SSIZE_T_MAX / elsize);
     nbytes = nelem * elsize;
 
+    if (nelem == 0 || elsize == 0)
+        goto redirect;
+
     if ((nbytes - 1) < SMALL_REQUEST_THRESHOLD) {
         LOCK();
         /*