https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104284
--- Comment #3 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The trunk branch has been updated by Marek Polacek <mpola...@gcc.gnu.org>: https://gcc.gnu.org/g:9fdac7e16c940fb6264e6ddaf99c761f1a64a054 commit r12-7805-g9fdac7e16c940fb6264e6ddaf99c761f1a64a054 Author: Marek Polacek <pola...@redhat.com> Date: Thu Mar 17 14:39:37 2022 -0400 c++: ICE with template code in constexpr [PR104284] Since r9-6073 cxx_eval_store_expression preevaluates the value to be stored, and that revealed a crash where a template code (here, code=IMPLICIT_CONV_EXPR) leaks into cxx_eval*. It happens because we're performing build_vec_init while processing a template, which calls get_temp_regvar which creates an INIT_EXPR. This INIT_EXPR's RHS contains an rvalue conversion so we create an IMPLICIT_CONV_EXPR. Its operand is not type-dependent and the whole INIT_EXPR is not type-dependent. So we call build_non_dependent_expr which, with -fchecking=2, calls fold_non_dependent_expr. At this point the expression still has an IMPLICIT_CONV_EXPR, which ought to be handled in instantiate_non_dependent_expr_internal. However, tsubst_copy_and_build doesn't handle INIT_EXPR; it will just call tsubst_copy which does nothing when args is null. So we fail to replace the IMPLICIT_CONV_EXPR and ICE. The problem is that we call build_vec_init in a template in the first place. We can avoid doing so by checking p_t_d before calling build_aggr_init in check_initializer. PR c++/104284 gcc/cp/ChangeLog: * decl.cc (check_initializer): Don't call build_aggr_init in a template. gcc/testsuite/ChangeLog: * g++.dg/cpp1y/constexpr-104284-1.C: New test. * g++.dg/cpp1y/constexpr-104284-2.C: New test. * g++.dg/cpp1y/constexpr-104284-3.C: New test. * g++.dg/cpp1y/constexpr-104284-4.C: New test.
