Fix a C compiler warning about unused cleanup code in buffer using functions...

Fix a C compiler warning about unused cleanup code in buffer using functions that always raise (found by clang in the bufaccess.pyx test).

Cython/Compiler/Nodes.py

@@ -2023,8 +2023,9 @@ class FuncDefNode(StatNode, BlockNode):
                     code.putln("%s = %s;" % (Naming.retval_cname, val))
                 elif not return_type.is_void:
                     code.putln("__Pyx_pretend_to_initialize(&%s);" % Naming.retval_cname)
+
         # ----- Error cleanup
-        if code.error_label in code.labels_used:
+        if code.label_used(code.error_label):
             if not self.body.is_terminator:
                 code.put_goto(code.return_label)
             code.put_label(code.error_label)
@@ -2107,6 +2108,7 @@ class FuncDefNode(StatNode, BlockNode):
             def align_error_path_gil_to_success_path(): pass
 
         # ----- Non-error return cleanup
+        if code.label_used(code.return_label) or not code.label_used(code.error_label):
             code.put_label(code.return_label)
 
             for entry in used_buffer_entries: