On Mon, Aug 29, 2016 at 04:02:33PM -0400, Jason Merrill wrote:
> 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".
Fixed.
> > @@ -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.
Done. But I couldn't figure out a testcase where the warning would trigger, so
not sure how important that is.
> > + 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.
Ok, done.
> > @@ -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.
Makes sense, fixed.
Thanks for looking into this. I'll post another version once it passes
testing.
Marek
