From 0a37463758dabc9647fa3d675dffdf43a737035d Mon Sep 17 00:00:00 2001 From: Patrick Palka Date: Tue, 19 Dec 2023 11:40:15 -0500 Subject: [PATCH] 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 using first_t = T; template struct traits; template struct traits> { }; // #1 template struct traits> { }; // #2 we correctly consider #2 to be more specialized than #1. But if the alias specialization appears as a nested template argument of another class template specialization, e.g. in template struct traits>> { }; // #1 template struct traits>> { }; // #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. PR c++/90679 gcc/cp/ChangeLog: * cp-tree.h (comp_template_args): Remove partial_order parameter. (template_args_equal): Likewise. * pt.cc (comparing_for_partial_ordering): New global flag. (iterative_hash_template_arg) : Hash the template and arguments for specializations that use structural equality. (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) : 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..7208c721b0b 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -1646,6 +1646,12 @@ register_specialization (tree spec, tree tmpl, tree args, bool is_friend, int comparing_specializations; int comparing_dependent_aliases; +/* 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; + /* Returns true iff two spec_entry nodes are equivalent. */ bool @@ -1894,6 +1900,11 @@ 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; } @@ -9322,7 +9333,7 @@ class_nttp_const_wrapper_p (tree t) /* Returns 1 if template args OT and NT are equivalent. */ int -template_args_equal (tree ot, tree nt, bool partial_order /* = false */) +template_args_equal (tree ot, tree nt) { if (nt == ot) return 1; @@ -9345,7 +9356,7 @@ template_args_equal (tree ot, tree nt, bool partial_order /* = false */) During partial ordering, however, we need to treat them normally so we can order uses of the same alias with different cv-qualification (79960). */ auto cso = make_temp_override (comparing_dependent_aliases); - if (!partial_order) + if (!comparing_for_partial_ordering) ++comparing_dependent_aliases; if (TREE_CODE (nt) == TREE_VEC || TREE_CODE (ot) == TREE_VEC) @@ -9393,8 +9404,7 @@ template_args_equal (tree ot, tree nt, bool partial_order /* = false */) bool comp_template_args (tree oldargs, tree newargs, - tree *oldarg_ptr /* = NULL */, tree *newarg_ptr /* = NULL */, - bool partial_order /* = false */) + tree *oldarg_ptr /* = NULL */, tree *newarg_ptr /* = NULL */) { if (oldargs == newargs) return true; @@ -9410,7 +9420,7 @@ comp_template_args (tree oldargs, tree newargs, tree nt = TREE_VEC_ELT (newargs, i); tree ot = TREE_VEC_ELT (oldargs, i); - if (! template_args_equal (ot, nt, partial_order)) + if (! template_args_equal (ot, nt)) { if (oldarg_ptr != NULL) *oldarg_ptr = ot; @@ -9422,10 +9432,13 @@ comp_template_args (tree oldargs, tree newargs, return true; } -inline bool +static bool comp_template_args_porder (tree oargs, tree nargs) { - return comp_template_args (oargs, nargs, NULL, NULL, true); + ++comparing_for_partial_ordering; + bool equal = comp_template_args (oargs, nargs); + --comparing_for_partial_ordering; + return equal; } /* Implement a freelist interface for objects of type T. @@ -28727,6 +28740,19 @@ any_template_arguments_need_structural_equality_p (tree args) mutated after the fact by duplicate_decls), so just require structural equality in this case (PR52830). */ return true; + else if (TYPE_P (arg) + && TYPE_STRUCTURAL_EQUALITY_P (arg) + && dependent_alias_template_spec_p (arg, nt_transparent)) + /* Require structural equality for specializations written + in terms of a dependent alias template specialization. */ + return true; + else if (CLASS_TYPE_P (arg) + && TYPE_TEMPLATE_INFO (arg) + && TYPE_STRUCTURAL_EQUALITY_P (arg)) + /* Require structural equality for specializations written + in terms of a class template specialization that itself + needs structural equality. */ + return true; } } } diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc index d26e73aaf95..d17b9b34891 100644 --- a/gcc/cp/tree.cc +++ b/gcc/cp/tree.cc @@ -4131,7 +4131,7 @@ cp_tree_equal (tree t1, tree t2) case TREE_VEC: /* These are template args. Really we should be getting the caller to do this as it knows it to be true. */ - if (!comp_template_args (t1, t2, NULL, NULL, false)) + if (!comp_template_args (t1, t2)) return false; return true; diff --git a/gcc/testsuite/g++.dg/cpp0x/alias-decl-75a.C b/gcc/testsuite/g++.dg/cpp0x/alias-decl-75a.C new file mode 100644 index 00000000000..8adbd6f65ac --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/alias-decl-75a.C @@ -0,0 +1,26 @@ +// PR c++/90679 +// A version of alias-decl-75.C where the specializations of the +// complex alias template first_t are dependent. +// { dg-do compile { target c++11 } } + +template +using first_t = T; + +template +struct A; + +template +struct traits; + +template +struct traits>> { + static constexpr int value = 1; +}; + +template +struct traits>> { + static constexpr int value = 2; +}; + +static_assert(traits>::value == 1, ""); +static_assert(traits>::value == 2, ""); // { dg-bogus "ambiguous" } diff --git a/gcc/testsuite/g++.dg/cpp0x/alias-decl-75b.C b/gcc/testsuite/g++.dg/cpp0x/alias-decl-75b.C new file mode 100644 index 00000000000..b89ea5cad1e --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp0x/alias-decl-75b.C @@ -0,0 +1,26 @@ +// PR c++/90679 +// A version of alias-decl-75a.C where the alias template specialization +// appears as a more deeply nested template argument. +// { dg-do compile { target c++11 } } + +template +using first_t = T; + +template +struct A; + +template +struct traits; + +template +struct traits>>> { + static constexpr int value = 1; +}; + +template +struct traits>>> { + static constexpr int value = 2; +}; + +static_assert(traits>>::value == 1, ""); +static_assert(traits>>::value == 2, ""); // { dg-bogus "ambiguous" }