Re: [PATCH] c++: Clear uninstantiated friend flag when instantiating [PR104234]

[Patrick Palka <ppalka@redhat.com>]

On Thu, 23 Nov 2023, Nathaniel Shead wrote:

> Bootstrapped and regtested on x86_64-pc-linux-gnu. I don't have write
> access.
> 
> -- >8 --
> 
> Otherwise attempting to get the originating module declaration ICEs
> because the DECL_CHAIN of an instantiated friend template is no longer
> its context.

Thanks for the patch!  I arrived at a similar fix back in January[1],
which Nathan reviewed[2], which then fell through the cracks...  My
patch was perhaps too ambitious as it tried to fix the ICE as well
as a follow-up module attachment issue.  But just clearing
DECL_UNINSTANTIATED_TEMPLATE_FRIEND_P (either in tsubst_template_decl or
more narrowly in tsubst_friend_class) seems pretty clearly correct and
fixes the reported ICEs so LGTM :) Thanks again!

[1]: https://gcc.gnu.org/pipermail/gcc-patches/2023-January/610593.html
[2]: https://gcc.gnu.org/pipermail/gcc-patches/2023-February/611215.html

> 
> 	PR c++/104234
>         PR c++/112580
> 
> gcc/cp/ChangeLog:
> 
> 	* pt.cc (tsubst_template_decl):
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/modules/pr104234.C: New test.
> 
> Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
> ---
>  gcc/cp/pt.cc                            |  2 ++
>  gcc/testsuite/g++.dg/modules/pr104234.C | 16 ++++++++++++++++
>  2 files changed, 18 insertions(+)
>  create mode 100644 gcc/testsuite/g++.dg/modules/pr104234.C
> 
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index ed681afb5d4..5e10a523e1a 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -14789,6 +14789,8 @@ tsubst_template_decl (tree t, tree args, tsubst_flags_t complain,
>    if (PRIMARY_TEMPLATE_P (t))
>      DECL_PRIMARY_TEMPLATE (r) = r;
>  
> +  DECL_UNINSTANTIATED_TEMPLATE_FRIEND_P (r) = false;
> +
>    if (!lambda_fntype && !class_p)
>      {
>        /* Record this non-type partial instantiation.  */
> diff --git a/gcc/testsuite/g++.dg/modules/pr104234.C b/gcc/testsuite/g++.dg/modules/pr104234.C
> new file mode 100644
> index 00000000000..d81f0d435bc
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/modules/pr104234.C
> @@ -0,0 +1,16 @@
> +// PR c++/104234
> +// { dg-additional-options "-fmodules-ts" }
> +
> +template <typename> struct _Node_handle_common {
> +  template <typename> friend class _Rb_tree;
> +};
> +struct _Hashtable {
> +  using node_type = _Node_handle_common<int>;
> +  node_type __trans_tmp_1;
> +};
> +template <typename> class _Rb_tree {
> +  struct _Rb_tree_impl {
> +    _Rb_tree_impl();
> +  } _M_impl;
> +};
> +_Rb_tree<int> _M_tmap_;
> -- 
> 2.42.0
> 
>