From: Jason Merrill <jason@redhat.com>
To: Patrick Palka <ppalka@redhat.com>, gcc-patches@gcc.gnu.org
Subject: Re: [PATCH] c++: bound ttp level lowering [PR109531]
Date: Mon, 17 Apr 2023 18:11:08 -0400 [thread overview]
Message-ID: <79e922cf-a6cb-99f7-6f91-03e85697e53a@redhat.com> (raw)
In-Reply-To: <20230417184419.4043285-1-ppalka@redhat.com>
On 4/17/23 14:44, Patrick Palka wrote:
> Here when level lowering the bound ttp TT<typename T::type> via the
> substitution T=C, we're neglecting to canonicalize (and therefore strip
> of simple typedefs) the resulting template arguments {A<int>} before
> determining its new canonical type via hash table lookup. This leads to
> an a hash mismatch ICE for the two equivalent types TT<int> and TT<A<int>>
> since iterative_hash_template_arg misbehaves for a non-canonicalized type
> argument.
>
> We can fix this by canonicalizing or coercing the substituted arguments
> directly, but given that creation and ordinary substitution of bound
> ttps both go through lookup_template_class, which in turn performs
> coercion/canonicalization, it seems best to make this code path go
> through lookup_template_class as well.
>
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk/13?
OK.
> PR c++/109531
>
> gcc/cp/ChangeLog:
>
> * pt.cc (tsubst) <case BOUND_TEMPLATE_TEMPLATE_PARM>:
> In the level-lowering case just use lookup_template_class
> to rebuild the bound ttp.
>
> gcc/testsuite/ChangeLog:
>
> * g++.dg/template/canon-type-20.C: New test.
> * g++.dg/template/ttp36.C: New test.
> ---
> gcc/cp/pt.cc | 39 ++++++++++---------
> gcc/testsuite/g++.dg/template/canon-type-20.C | 18 +++++++++
> gcc/testsuite/g++.dg/template/ttp36.C | 12 ++++++
> 3 files changed, 50 insertions(+), 19 deletions(-)
> create mode 100644 gcc/testsuite/g++.dg/template/canon-type-20.C
> create mode 100644 gcc/testsuite/g++.dg/template/ttp36.C
>
> diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
> index fcc8e0d1d57..e065ace5c55 100644
> --- a/gcc/cp/pt.cc
> +++ b/gcc/cp/pt.cc
> @@ -16232,7 +16232,6 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
> {
> case TEMPLATE_TYPE_PARM:
> case TEMPLATE_TEMPLATE_PARM:
> - case BOUND_TEMPLATE_TEMPLATE_PARM:
> if (cp_type_quals (t))
> {
> r = tsubst (TYPE_MAIN_VARIANT (t), args, complain, in_decl);
> @@ -16274,24 +16273,6 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
> only instantiated during satisfaction. */
> PLACEHOLDER_TYPE_CONSTRAINTS_INFO (r) = ci;
>
> - if (code == BOUND_TEMPLATE_TEMPLATE_PARM)
> - {
> - tree tinfo = TYPE_TEMPLATE_INFO (t);
> - /* We might need to substitute into the types of non-type
> - template parameters. */
> - tree tmpl = tsubst (TI_TEMPLATE (tinfo), args,
> - complain, in_decl);
> - if (tmpl == error_mark_node)
> - return error_mark_node;
> - tree argvec = tsubst (TI_ARGS (tinfo), args,
> - complain, in_decl);
> - if (argvec == error_mark_node)
> - return error_mark_node;
> -
> - TEMPLATE_TEMPLATE_PARM_TEMPLATE_INFO (r)
> - = build_template_info (tmpl, argvec);
> - }
> -
> if (TYPE_STRUCTURAL_EQUALITY_P (t))
> SET_TYPE_STRUCTURAL_EQUALITY (r);
> else
> @@ -16299,6 +16280,26 @@ tsubst (tree t, tree args, tsubst_flags_t complain, tree in_decl)
> }
> break;
>
> + case BOUND_TEMPLATE_TEMPLATE_PARM:
> + {
> + tree tinfo = TYPE_TEMPLATE_INFO (t);
> + /* We might need to substitute into the types of non-type
> + template parameters. This also lowers the level of
> + the ttp appropriately. */
> + tree tmpl = tsubst (TI_TEMPLATE (tinfo), args,
> + complain, in_decl);
> + if (tmpl == error_mark_node)
> + return error_mark_node;
> + tree argvec = tsubst (TI_ARGS (tinfo), args,
> + complain, in_decl);
> + if (argvec == error_mark_node)
> + return error_mark_node;
> + r = lookup_template_class (tmpl, argvec, in_decl, NULL_TREE,
> + /*entering_scope=*/false, complain);
> + r = cp_build_qualified_type (r, cp_type_quals (t), complain);
> + break;
> + }
> +
> case TEMPLATE_PARM_INDEX:
> /* OK, now substitute the type of the non-type parameter. We
> couldn't do it earlier because it might be an auto parameter,
> diff --git a/gcc/testsuite/g++.dg/template/canon-type-20.C b/gcc/testsuite/g++.dg/template/canon-type-20.C
> new file mode 100644
> index 00000000000..e40261037e5
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/canon-type-20.C
> @@ -0,0 +1,18 @@
> +// PR c++/109531
> +// { dg-do compile { target c++11 } }
> +// { dg-additional-options "--param=hash-table-verification-limit=1000" }
> +
> +template<class T>
> +using A = int;
> +
> +struct B { using type = int; };
> +struct C { using type = A<int>; };
> +
> +template<class T>
> +struct D {
> + template<template<class> class TT>
> + TT<typename T::type> f ();
> +};
> +
> +template struct D<B>;
> +template struct D<C>;
> diff --git a/gcc/testsuite/g++.dg/template/ttp36.C b/gcc/testsuite/g++.dg/template/ttp36.C
> new file mode 100644
> index 00000000000..2df00855cf7
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/template/ttp36.C
> @@ -0,0 +1,12 @@
> +// Verify we propagate cv-quals when level-lowering a bound ttp.
> +
> +template<class T>
> +struct B {
> + template<template<class> class TT>
> + void f(const TT<T> *);
> +
> + template<template<class> class TT>
> + void f(TT<T> *); // { dg-bogus "cannot be overloaded" }
> +};
> +
> +template struct B<int>;
prev parent reply other threads:[~2023-04-17 22:11 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-17 18:44 Patrick Palka
2023-04-17 22:11 ` Jason Merrill [this message]
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