https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97412
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-10 branch has been updated by Patrick Palka <ppa...@gcc.gnu.org>: https://gcc.gnu.org/g:5ab7959ee18980d676892fa6579f1ca09c5ecc08 commit r10-8957-g5ab7959ee18980d676892fa6579f1ca09c5ecc08 Author: Patrick Palka <ppa...@redhat.com> Date: Thu Oct 29 14:02:59 2020 -0400 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. (cherry picked from commit 5681668765e233735b4c5e6a305e73ae1f80a328)
