On Mon, Aug 29, 2016 at 7:58 AM, Marek Polacek <pola...@redhat.com> wrote:
> --- gcc/gcc/cp/parser.c
> +++ gcc/gcc/cp/parser.c
> @@ -5135,6 +5135,31 @@ cp_parser_primary_expression (cp_parser *parser,
> case RID_AT_SELECTOR:
> return cp_parser_objc_expression (parser);
>
> + case RID_ATTRIBUTE:
> + {
> + /* This might be __attribute__((fallthrough));. */
> + tree attr = cp_parser_gnu_attributes_opt (parser);
> + if (attr != NULL_TREE
> + && is_attribute_p ("fallthrough", get_attribute_name (attr)))
> + {
> + tree fn = build_call_expr_internal_loc (token->location,
> + IFN_FALLTHROUGH,
> + void_type_node, 0);
> + return cp_expr (fn, token->location);
> + }
> + else if (cp_lexer_next_token_is (parser->lexer, CPP_SEMICOLON))
> + {
> + cp_parser_error (parser, "only attribute %<fallthrough%> "
> + "can be used");
Let's say "can be applied to a null statement".
> @@ -10585,15 +10610,26 @@ cp_parser_statement (cp_parser* parser, tree
> in_statement_expr,
> }
> /* Look for an expression-statement instead. */
> statement = cp_parser_expression_statement (parser, in_statement_expr);
> +
> + /* Handle [[fallthrough]];. */
> + if (std_attrs != NULL_TREE
> + && is_attribute_p ("fallthrough", get_attribute_name (std_attrs))
> + && statement == NULL_TREE)
> + {
> + tree fn = build_call_expr_internal_loc (statement_location,
> + IFN_FALLTHROUGH,
> + void_type_node, 0);
Let's use the 'statement' variable rather than a new variable fn so
that we set the call's location below. Let's also warn here about
[[fallthrough]] on non-null expression statements.
> + finish_expr_stmt (fn);
Let's clear std_attrs here...
> + }
> /* Set the line number for the statement. */
> if (statement && STATEMENT_CODE_P (TREE_CODE (statement)))
> SET_EXPR_LOCATION (statement, statement_location);
>
> - /* Note that for now, we don't do anything with c++11 statements
> - parsed at this level. */
> - if (std_attrs != NULL_TREE)
> + /* Allow "[[fallthrough]];", but warn otherwise. */
> + if (std_attrs != NULL_TREE
> + && !is_attribute_p ("fallthrough", get_attribute_name (std_attrs)))
...so we don't need to check for fallthrough here.
> @@ -24114,6 +24164,16 @@ cp_parser_std_attribute (cp_parser *parser)
> " use %<gnu::deprecated%>");
> TREE_PURPOSE (TREE_PURPOSE (attribute)) = get_identifier ("gnu");
> }
> + /* C++17 fallthrough attribute is equivalent to GNU's. */
> + else if (cxx_dialect >= cxx11
There's no point checking this, here or for attribute deprecated; if
we're in this function, we must be in C++11 or above. Let's drop the
check in both places.
Jason
