On Thu, Jun 29, 2023 at 11:22:55AM -0400, Patrick Palka via Gcc-patches wrote:
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk/13?
>
> -- >8 --
>
> cp_fold is neglecting to propagate CONSTRUCTOR_MUTABLE_POISON when folding
> a CONSTRUCTOR initializer, which for the below testcase causes us to fail
> to reject a mutable member access of a constexpr variable during constexpr
> evaluation.
LGTM.
> PR c++/110463
>
> gcc/cp/ChangeLog:
>
> * cp-gimplify.cc (cp_fold) <case CONSTRUCTOR>: Propagate
> CONSTRUCTOR_MUTABLE_POISON.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/cpp0x/constexpr-mutable6.C: New test.
> ---
> gcc/cp/cp-gimplify.cc | 2 ++
> .../g++.dg/cpp0x/constexpr-mutable6.C | 18 ++++++++++++++++++
> 2 files changed, 20 insertions(+)
> create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-mutable6.C
>
> diff --git a/gcc/cp/cp-gimplify.cc b/gcc/cp/cp-gimplify.cc
> index 853b1e44236..f5734197774 100644
> --- a/gcc/cp/cp-gimplify.cc
> +++ b/gcc/cp/cp-gimplify.cc
> @@ -3079,6 +3079,8 @@ cp_fold (tree x, fold_flags_t flags)
> x = build_constructor (TREE_TYPE (x), nelts);
> CONSTRUCTOR_PLACEHOLDER_BOUNDARY (x)
> = CONSTRUCTOR_PLACEHOLDER_BOUNDARY (org_x);
> + CONSTRUCTOR_MUTABLE_POISON (x)
> + = CONSTRUCTOR_MUTABLE_POISON (org_x);
> }
> if (VECTOR_TYPE_P (TREE_TYPE (x)))
> x = fold (x);
> diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-mutable6.C
> b/gcc/testsuite/g++.dg/cpp0x/constexpr-mutable6.C
> new file mode 100644
> index 00000000000..2c946e388ab
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-mutable6.C
> @@ -0,0 +1,18 @@
> +// PR c++/110463
> +// { dg-do compile { target c++11 } }
> +
> +struct U {
> + mutable int x = 1;
> +};
> +
> +struct V {
> + mutable int y = 1+1;
> +};
> +
> +int main() {
> + constexpr U u = {};
> + constexpr int x = u.x; // { dg-error "mutable" }
> +
> + constexpr V v = {};
> + constexpr int y = v.y; // { dg-error "mutable" }
> +}
> --
> 2.41.0.199.ga9e066fa63
>
Marek
