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. Eliding the IMPLICIT_CONV_EXPR in this particular case would be too risky, so we could do if (TREE_CODE (t) == INIT_EXPR) t = TREE_OPERAND (t, 1); in fold_non_dependent_expr, but that feels too ad hoc. So it might make sense to actually take care of INIT_EXPR in tsubst_c_and_b. Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/11? PR c++/104284 gcc/cp/ChangeLog: * pt.cc (tsubst_copy_and_build): Handle INIT_EXPR. gcc/testsuite/ChangeLog: * g++.dg/cpp1y/constexpr-104284.C: New test. --- gcc/cp/pt.cc | 8 ++++++++ gcc/testsuite/g++.dg/cpp1y/constexpr-104284.C | 17 +++++++++++++++++ 2 files changed, 25 insertions(+) create mode 100644 gcc/testsuite/g++.dg/cpp1y/constexpr-104284.C diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index f7ee33a6dfd..e8920f98e4d 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -21289,6 +21289,14 @@ tsubst_copy_and_build (tree t, with constant operands. */ RETURN (t); + case INIT_EXPR: + { + tree op0 = RECUR (TREE_OPERAND (t, 0)); + tree op1 = RECUR (TREE_OPERAND (t, 1)); + RETURN (build2_loc (input_location, INIT_EXPR, TREE_TYPE (op0), + op0, op1)); + } + case NON_LVALUE_EXPR: case VIEW_CONVERT_EXPR: if (location_wrapper_p (t)) diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-104284.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284.C new file mode 100644 index 00000000000..f60033069e4 --- /dev/null +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-104284.C @@ -0,0 +1,17 @@ +// PR c++/104284 +// { dg-do compile { target c++14 } } +// { dg-additional-options "-fchecking=2" } + +struct S { + char c{}; +}; + +auto x = [](auto) { constexpr S s[]{{}}; }; + +template<class> +constexpr void gn () +{ + constexpr S s[]{{}}; +} + +static_assert ((gn<int>(), true), ""); base-commit: b5417a0ba7e26bec2abf05cad6c6ef840a9be41c -- 2.35.1