Ping.
On Thu, Sep 05, 2019 at 10:24:55PM -0400, Marek Polacek wrote:
> Compiling this testcase results in a bogus "invalid cast" error; this occurs
> since the introduction of location wrappers in finish_id_expression.
>
> Here we are parsing the decltype expression via cp_parser_decltype_expr which
> can lead to calling various fold_* and c-family routines. They use
> non_lvalue_loc, but that won't create a NON_LVALUE_EXPR wrapper around a
> location
> wrapper.
>
> So before the location wrappers addition cp_parser_decltype_expr would return
> NON_LVALUE_EXPR <c>. Now it returns VIEW_CONVERT_EXPR<float *>(c), but the
> STRIP_ANY_LOCATION_WRAPPER immediately following it strips the location
> wrapper,
> and suddenly we don't know whether we have an lvalue anymore. And that's sad
> because then decltype produces the wrong type, causing nonsense errors.
>
> Bootstrapped/regtested on x86_64-linux, ok for trunk and 9?
>
> 2019-09-05 Marek Polacek <pola...@redhat.com>
>
> PR c++/91678 - wrong error with decltype and location wrapper.
> * parser.c (cp_parser_decltype): Use auto_suppress_location_wrappers
> sentinel. Don't strip location wrappers.
>
> * g++.dg/cpp0x/decltype73.C: New test.
>
> diff --git gcc/cp/parser.c gcc/cp/parser.c
> index baa60b8834e..b3c7bff5988 100644
> --- gcc/cp/parser.c
> +++ gcc/cp/parser.c
> @@ -14729,8 +14729,13 @@ cp_parser_decltype (cp_parser *parser)
> /* Do not warn about problems with the expression. */
> ++c_inhibit_evaluation_warnings;
>
> + /* Don't create wrapper nodes within decltype. non_lvalue_loc won't
> + create a NON_LVALUE_EXPR wrapper around a location wrapper, and a
> + subsequent STRIP_ANY_LOCATION_WRAPPER would destroy the information
> + about lvalueness of the expression. */
> + auto_suppress_location_wrappers sentinel;
> +
> expr = cp_parser_decltype_expr (parser,
> id_expression_or_member_access_p);
> - STRIP_ANY_LOCATION_WRAPPER (expr);
>
> /* Go back to evaluating expressions. */
> --cp_unevaluated_operand;
> diff --git gcc/testsuite/g++.dg/cpp0x/decltype73.C
> gcc/testsuite/g++.dg/cpp0x/decltype73.C
> new file mode 100644
> index 00000000000..cbe94a898e3
> --- /dev/null
> +++ gcc/testsuite/g++.dg/cpp0x/decltype73.C
> @@ -0,0 +1,4 @@
> +// PR c++/91678 - wrong error with decltype and location wrapper.
> +// { dg-do compile { target c++11 } }
> +
> +float* test(float* c) { return (decltype(c + 0))(float*)c; }
