From 72394d38d929c72cad6cf706a0e790b5934f2bf1 Mon Sep 17 00:00:00 2001 From: Barrett Adair Date: Wed, 15 Sep 2021 15:26:22 -0500 Subject: c++: fix template instantiation comparison in redeclarations This change fixes a primordial c++11 frontend defect where function template redeclarations with trailing return types that used dependent sizeof/alignof/noexcept expressions in template value arguments failed to compare as equivalent to the identical primary template declaration. By forcing structural AST comparison of the template arguments, we no longer require TYPE_CANONICAL to match in this case. The new canon-type-{15..18}.C tests failed with all prior GCC versions, where the redeclarations were incorrectly reported as ambiguous overloads. The new dependent-name{15,16}.C tests are regression tests for sneaky problems encountered during development of this fix. Note that this fix does not address the use of parm objects' constexpr members as template arguments within a declaration (a superficially similar longstanding defect). gcc/cp/ChangeLog: * pt.c (find_parm_usage_r): New walk_tree callback to find func parms. (any_template_arguments_need_structural_equality_p): New special case. gcc/testsuite/ChangeLog: * g++.dg/cpp0x/constexpr-52830.C: Remove unwanted dg-ice. * g++.dg/template/canon-type-15.C: New test. * g++.dg/template/canon-type-16.C: New test. * g++.dg/template/canon-type-17.C: New test. * g++.dg/template/canon-type-18.C: New test. * g++.dg/template/dependent-name15.C: New regression test. * g++.dg/template/dependent-name16.C: New regression test. --- gcc/cp/pt.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'gcc/cp') diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c index 4d42899..048bbc4 100644 --- a/gcc/cp/pt.c +++ b/gcc/cp/pt.c @@ -27813,6 +27813,20 @@ dependent_template_arg_p (tree arg) return value_dependent_expression_p (arg); } +/* Identify any expressions that use function parms. */ + +static tree +find_parm_usage_r (tree *tp, int *walk_subtrees, void*) +{ + tree t = *tp; + if (TREE_CODE (t) == PARM_DECL) + { + *walk_subtrees = 0; + return t; + } + return NULL_TREE; +} + /* Returns true if ARGS (a collection of template arguments) contains any types that require structural equality testing. */ @@ -27857,6 +27871,13 @@ any_template_arguments_need_structural_equality_p (tree args) else if (!TYPE_P (arg) && TREE_TYPE (arg) && TYPE_STRUCTURAL_EQUALITY_P (TREE_TYPE (arg))) return true; + /* Checking current_function_decl because this structural + comparison is only necessary for redeclaration. */ + else if (!current_function_decl + && dependent_template_arg_p (arg) + && (cp_walk_tree_without_duplicates + (&arg, find_parm_usage_r, NULL))) + return true; } } } -- cgit v1.1