From 5681668765e233735b4c5e6a305e73ae1f80a328 Mon Sep 17 00:00:00 2001 From: Patrick Palka Date: Thu, 29 Oct 2020 14:02:59 -0400 Subject: [PATCH] c++: Tolerate empty initial args during normalization [PR97412] When normalizing the constraint-expression of a nested-requirement, we pass NULL_TREE as the initial template arguments for normalization, but tsubst_argument_pack is not prepared to handle a NULL_TREE args vector. This causes us to ICE when normalizing a variadic concept as part of a nested-requirement. This patch fixes the ICE by guarding the call to tsubst_template_args in normalize_concept_check appropriately. This will also enable us to simplify many of the normalization routines to just pass NULL_TREE (instead of a set of generic template arguments) as the initial template arguments. gcc/cp/ChangeLog: PR c++/97412 * constraint.cc (normalize_concept_check): Don't call tsubst_template_args when 'args' is NULL. gcc/testsuite/ChangeLog: PR c++/97412 * g++.dg/cpp2a/concepts-variadic2.C: New test. --- gcc/cp/constraint.cc | 3 ++- gcc/testsuite/g++.dg/cpp2a/concepts-variadic2.C | 12 ++++++++++++ 2 files changed, 14 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/cpp2a/concepts-variadic2.C diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc index f4f5174eff3..75457a2dd60 100644 --- a/gcc/cp/constraint.cc +++ b/gcc/cp/constraint.cc @@ -686,7 +686,8 @@ normalize_concept_check (tree check, tree args, norm_info info) } /* Substitute through the arguments of the concept check. */ - targs = tsubst_template_args (targs, args, info.complain, info.in_decl); + if (args) + targs = tsubst_template_args (targs, args, info.complain, info.in_decl); if (targs == error_mark_node) return error_mark_node; diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-variadic2.C b/gcc/testsuite/g++.dg/cpp2a/concepts-variadic2.C new file mode 100644 index 00000000000..ce61aef5481 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp2a/concepts-variadic2.C @@ -0,0 +1,12 @@ +// PR c++/97412 +// { dg-do compile { target c++20 } } + +template +concept call_bar_with = requires(T t, TArgs... args) { + t.bar(args...); +}; + +template +concept foo = requires { + requires call_bar_with; +}; -- 2.30.2