Hard-disable the MergeVTables() step during the extension type setup when...

Hard-disable the MergeVTables() step during the extension type setup when using the Limited API. There might be a way to make it work, but it currently won't.

Also see https://github.com/cython/cython/pull/4107

Cython/Compiler/Nodes.py

@@ -5371,12 +5371,13 @@ class CClassDefNode(ClassDefNode):
                         typeobj_cname,
                         type.vtabptr_cname,
                         code.error_goto(entry.pos)))
-                code.putln("#endif")
+                # TODO: find a way to make this work with the Limited API!
                 code.globalstate.use_utility_code(
                     UtilityCode.load_cached('MergeVTables', 'ImportExport.c'))
                 code.putln("if (__Pyx_MergeVtables(&%s) < 0) %s" % (
                     typeobj_cname,
                     code.error_goto(entry.pos)))
+                code.putln("#endif")
             if not type.scope.is_internal and not type.scope.directives.get('internal'):
                 # scope.is_internal is set for types defined by
                 # Cython (such as closures), the 'internal'

Cython/Utility/ImportExport.c

@@ -748,10 +748,14 @@ bad:
 /////////////// MergeVTables.proto ///////////////
 //@requires: GetVTable
 
+// TODO: find a way to make this work with the Limited API!
+#if !CYTHON_COMPILING_IN_LIMITED_API
 static int __Pyx_MergeVtables(PyTypeObject *type); /*proto*/
+#endif
 
 /////////////// MergeVTables ///////////////
 
+#if !CYTHON_COMPILING_IN_LIMITED_API
 static int __Pyx_MergeVtables(PyTypeObject *type) {
     int i;
     void** base_vtables;
@@ -808,6 +812,7 @@ bad:
     free(base_vtables);
     return -1;
 }
+#endif
 
 
 /////////////// ImportNumPyArray.proto ///////////////