Ping.
On Mon, Nov 25, 2024 at 04:46:56PM -0500, Marek Polacek wrote:
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/14?
>
> -- >8 --
> In a template, for
>
> union {
> union {
> T d;
> };
> };
>
> build_anon_union_vars crates a malformed COMPONENT_REF: we have no
> DECL_NAME for the nested anon union so we create something like "object.".
> Most of the front end doesn't seem to care, but if such a tree gets to
> potential_constant_expression, it can cause a crash.
>
> I suppose we can use any name for the COMPONENT_REF's member. tsubst_stmt
> should build up a proper one in:
>
> if (VAR_P (decl) && !DECL_NAME (decl)
> && ANON_AGGR_TYPE_P (TREE_TYPE (decl)))
> /* Anonymous aggregates are a special case. */
> finish_anon_union (decl);
>
> PR c++/117153
>
> gcc/cp/ChangeLog:
>
> * decl2.cc (build_anon_union_vars): If DECL_NAME is empty, use
> an anonymous name for the second operand of a COMPONENT_REF.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/other/anon-union6.C: New test.
> * g++.dg/other/anon-union7.C: New test.
> ---
> gcc/cp/decl2.cc | 5 ++++-
> gcc/testsuite/g++.dg/other/anon-union6.C | 13 +++++++++++++
> gcc/testsuite/g++.dg/other/anon-union7.C | 16 ++++++++++++++++
> 3 files changed, 33 insertions(+), 1 deletion(-)
> create mode 100644 gcc/testsuite/g++.dg/other/anon-union6.C
> create mode 100644 gcc/testsuite/g++.dg/other/anon-union7.C
>
> diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc
> index bc3a9d0e922..1383cbb660c 100644
> --- a/gcc/cp/decl2.cc
> +++ b/gcc/cp/decl2.cc
> @@ -1959,7 +1959,10 @@ build_anon_union_vars (tree type, tree object)
>
> if (processing_template_decl)
> ref = build_min_nt_loc (UNKNOWN_LOCATION, COMPONENT_REF, object,
> - DECL_NAME (field), NULL_TREE);
> + (DECL_NAME (field)
> + ? DECL_NAME (field)
> + : make_anon_name ()),
> + NULL_TREE);
> else
> ref = build_class_member_access_expr (object, field, NULL_TREE,
> false, tf_warning_or_error);
> diff --git a/gcc/testsuite/g++.dg/other/anon-union6.C
> b/gcc/testsuite/g++.dg/other/anon-union6.C
> new file mode 100644
> index 00000000000..d1cde30f790
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/other/anon-union6.C
> @@ -0,0 +1,13 @@
> +// PR c++/117153
> +// { dg-do compile }
> +
> +template<typename T>
> +void f() {
> + union {
> + union {
> + T d;
> + };
> + };
> + (void) (d + 0);
> +}
> +template void f<double>();
> diff --git a/gcc/testsuite/g++.dg/other/anon-union7.C
> b/gcc/testsuite/g++.dg/other/anon-union7.C
> new file mode 100644
> index 00000000000..e89334a5d0e
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/other/anon-union7.C
> @@ -0,0 +1,16 @@
> +// PR c++/117153
> +// { dg-do compile { target c++11 } }
> +
> +using U = union { union { int a; }; };
> +
> +U
> +foo ()
> +{
> + return {};
> +}
> +
> +void
> +g ()
> +{
> + [[maybe_unused]] auto u = foo ();
> +}
>
> base-commit: 4b09e2c67ef593db171b0755b46378964421782b
> --
> 2.47.0
>
Marek
