On 12/15/23 14:07, Patrick Palka wrote:
On Thu, 1 Jun 2023, Patrick Palka wrote:
During partial ordering, we want to look through dependent alias
template specializations within template arguments and otherwise
treat them as opaque in other contexts (see e.g. r7-7116-g0c942f3edab108
and r11-7011-g6e0a231a4aa240). To that end template_args_equal was
given a partial_order flag that controls this behavior. This flag
does the right thing when a dependent alias template specialization
appears as template argument of the partial specialization, e.g. in
template<class T, class...> using first_t = T;
template<class T> struct traits;
template<class T> struct traits<first_t<T, T&>> { }; // #1
template<class T> struct traits<first_t<const T, T&>> { }; // #2
we correctly consider #2 to be more specialized than #1. But if
the alias specialization appears as a template argument of another
class template specialization, e.g. in
template<class T> struct traits<A<first_t<T, T&>>> { }; // #1
template<class T> struct traits<A<first_t<const T, T&>>> { }; // #2
then we incorrectly consider #1 and #2 to be unordered. This is because
1. we don't propagate the flag to recursive template_args_equal calls
2. we don't use structural equality for class template specializations
written in terms of dependent alias template specializations
This patch fixes the first issue by turning the partial_order flag into
a global. This patch fixes the second issue by making us propagate
structural equality appropriately when building a class template
specialization. In passing this patch also improves hashing of
specializations that use structural equality.
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk?
PR c++/90679
gcc/cp/ChangeLog:
* cp-tree.h (comp_template_args): Remove partial_order
parameter.
(template_args_equal): Likewise.
* pt.cc (iterative_hash_template_arg) <case tcc_type>: Hash
the template and arguments for specializations that use
structural equality.
(comparing_for_partial_ordering): New flag.
(template_args_equal): Remove partial order parameter and
use comparing_for_partial_ordering instead.
(comp_template_args): Likewise.
(comp_template_args_porder): Set comparing_for_partial_ordering
instead. Make static.
(any_template_arguments_need_structural_equality_p): Return true
for an argument that's a dependent alias template specialization
or a class template specialization that itself needs structural
equality.
* tree.cc (cp_tree_equal) <case TREE_VEC>: Adjust call to
comp_template_args.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/alias-decl-75a.C: New test.
* g++.dg/cpp0x/alias-decl-75b.C: New test.
Ping. Here's the rebased patch:
-- >8 --
Subject: [PATCH 2/2] c++: partial ordering and dep alias tmpl specs [PR90679]
During partial ordering, we want to look through dependent alias
template specializations within template arguments and otherwise
treat them as opaque in other contexts (see e.g. r7-7116-g0c942f3edab108
and r11-7011-g6e0a231a4aa240). To that end template_args_equal was
given a partial_order flag that controls this behavior. This flag
does the right thing when a dependent alias template specialization
appears as template argument of the partial specialization, e.g. in
template<class T, class...> using first_t = T;
template<class T> struct traits;
template<class T> struct traits<first_t<T, T&>> { }; // #1
template<class T> struct traits<first_t<const T, T&>> { }; // #2
we correctly consider #2 to be more specialized than #1. But if
the alias specialization appears as a template argument of another
class template specialization, e.g. in
template<class T> struct traits<A<first_t<T, T&>>> { }; // #1
template<class T> struct traits<A<first_t<const T, T&>>> { }; // #2
then we incorrectly consider #1 and #2 to be unordered. This is because
1. we don't propagate the flag to recursive template_args_equal calls
2. we don't use structural equality for class template specializations
written in terms of dependent alias template specializations
This patch fixes the first issue by turning the partial_order flag into
a global. This patch fixes the second issue by making us propagate
structural equality appropriately when building a class template
specialization. In passing this patch also improves hashing of
specializations that use structural equality.
Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
trunk?
PR c++/90679
gcc/cp/ChangeLog:
* cp-tree.h (comp_template_args): Remove partial_order
parameter.
(template_args_equal): Likewise.
* pt.cc (iterative_hash_template_arg) <case tcc_type>: Hash
the template and arguments for specializations that use
structural equality.
(comparing_for_partial_ordering): New flag.
(template_args_equal): Remove partial order parameter and
use comparing_for_partial_ordering instead.
(comp_template_args): Likewise.
(comp_template_args_porder): Set comparing_for_partial_ordering
instead. Make static.
(any_template_arguments_need_structural_equality_p): Return true
for an argument that's a dependent alias template specialization
or a class template specialization that itself needs structural
equality.
* tree.cc (cp_tree_equal) <case TREE_VEC>: Adjust call to
comp_template_args.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/alias-decl-75a.C: New test.
* g++.dg/cpp0x/alias-decl-75b.C: New test.
---
gcc/cp/cp-tree.h | 4 +--
gcc/cp/pt.cc | 40 +++++++++++++++++----
gcc/cp/tree.cc | 2 +-
gcc/testsuite/g++.dg/cpp0x/alias-decl-75a.C | 26 ++++++++++++++
gcc/testsuite/g++.dg/cpp0x/alias-decl-75b.C | 26 ++++++++++++++
5 files changed, 88 insertions(+), 10 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/alias-decl-75a.C
create mode 100644 gcc/testsuite/g++.dg/cpp0x/alias-decl-75b.C
diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 85980c9ad9b..1979572c365 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -7507,8 +7507,8 @@ extern int template_class_depth (tree);
extern int is_specialization_of (tree, tree);
extern bool is_specialization_of_friend (tree, tree);
extern bool comp_template_args (tree, tree, tree * =
NULL,
- tree * = NULL, bool = false);
-extern int template_args_equal (tree, tree, bool = false);
+ tree * = NULL);
+extern int template_args_equal (tree, tree);
extern tree maybe_process_partial_specialization (tree);
extern tree most_specialized_instantiation (tree);
extern tree most_specialized_partial_spec (tree, tsubst_flags_t, bool =
false);
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index a3a79713236..6b0ef496dc5 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -1894,6 +1894,11 @@ iterative_hash_template_arg (tree arg, hashval_t val)
default:
if (tree canonical = TYPE_CANONICAL (arg))
val = iterative_hash_object (TYPE_HASH (canonical), val);
+ else if (tree ti = TYPE_TEMPLATE_INFO (arg))
+ {
+ val = iterative_hash_template_arg (TI_TEMPLATE (ti), val);
+ val = iterative_hash_template_arg (TI_ARGS (ti), val);
+ }
break;
}
@@ -9306,6 +9311,12 @@ coerce_template_parms (tree parms,
return return_full_args ? new_args : new_inner_args;
}
+/* Whether we are comparing template arguments during partial ordering
+ (and therefore want the comparison to look through dependent alias
+ template specializations). */
+
+static int comparing_for_partial_ordering;
How about putting this next to comparing_dependent_aliases? OK with
that change.
Jason
