On Tue, 18 Jul 2023, Marek Polacek via Gcc-patches wrote:
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk and branches?
Looks reasonable to me.
Though I wonder if we could also fix this by not checking potentiality
at all in this case? The problematic call to is_rvalue_constant_expression
happens from cp_parser_constant_expression with 'allow_non_constant' != 0
and with 'non_constant_p' being a dummy out argument that comes from
cp_parser_functional_cast, so the result of is_rvalue_constant_expression
is effectively unused in this case, and we should be able to safely elide
it when 'allow_non_constant && non_constant_p == nullptr'.
Relatedly, ISTM the member cp_parser::non_integral_constant_expression_p
is also effectively unused and could be removed?
>
> -- >8 --
>
> is_really_empty_class is liable to crash when it gets an incomplete
> or dependent type. Since r11-557, we pass the yet-uninstantiated
> class type S<0> of the PARM_DECL s to is_really_empty_class -- because
> of the potential_rvalue_constant_expression -> is_rvalue_constant_expression
> change in cp_parser_constant_expression. Here we're not parsing
> a template so we did not check COMPLETE_TYPE_P as we should.
>
> PR c++/110106
>
> gcc/cp/ChangeLog:
>
> * constexpr.cc (potential_constant_expression_1): Check COMPLETE_TYPE_P
> even when !processing_template_decl.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp0x/noexcept80.C: New test.
> ---
> gcc/cp/constexpr.cc | 2 +-
> gcc/testsuite/g++.dg/cpp0x/noexcept80.C | 12 ++++++++++++
> 2 files changed, 13 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/g++.dg/cpp0x/noexcept80.C
>
> diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
> index 6e8f1c2b61e..1f59c5472fb 100644
> --- a/gcc/cp/constexpr.cc
> +++ b/gcc/cp/constexpr.cc
> @@ -9116,7 +9116,7 @@ potential_constant_expression_1 (tree t, bool
> want_rval, bool strict, bool now,
> if (now && want_rval)
> {
> tree type = TREE_TYPE (t);
> - if ((processing_template_decl && !COMPLETE_TYPE_P (type))
> + if (!COMPLETE_TYPE_P (type)
> || dependent_type_p (type)
> || is_really_empty_class (type, /*ignore_vptr*/false))
> /* An empty class has no data to read. */
> diff --git a/gcc/testsuite/g++.dg/cpp0x/noexcept80.C
> b/gcc/testsuite/g++.dg/cpp0x/noexcept80.C
> new file mode 100644
> index 00000000000..3e90af747e2
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/noexcept80.C
> @@ -0,0 +1,12 @@
> +// PR c++/110106
> +// { dg-do compile { target c++11 } }
> +
> +template<int> struct S
> +{
> +};
> +
> +struct G {
> + G(S<0>);
> +};
> +
> +void y(S<0> s) noexcept(noexcept(G{s}));
>
> base-commit: fca089e8a47314a40ad93527ba9f9d0d374b3afb
> --
> 2.41.0
>
>
