From 6c7905a9f10d28dfd27ddf21d3bf38a3e261ee10 Mon Sep 17 00:00:00 2001 From: Jason Merrill Date: Tue, 12 Apr 2022 17:46:59 -0400 Subject: [PATCH] c++: empty base constexpr -fno-elide-ctors [PR105245] The patch for 100111 extended our handling of empty base elision to the case where the derived class has no other fields, but we still need to make sure that there's some initializer for the derived object. PR c++/105245 PR c++/100111 gcc/cp/ChangeLog: * constexpr.c (cxx_eval_store_expression): Build a CONSTRUCTOR as needed in empty base handling. gcc/testsuite/ChangeLog: * g++.dg/cpp1y/constexpr-empty2.C: Add -fno-elide-constructors. --- gcc/cp/constexpr.c | 6 ++++++ gcc/testsuite/g++.dg/cpp1y/constexpr-empty2.C | 1 + 2 files changed, 7 insertions(+) diff --git a/gcc/cp/constexpr.c b/gcc/cp/constexpr.c index 28b0a88a6582..31af214a28c8 100644 --- a/gcc/cp/constexpr.c +++ b/gcc/cp/constexpr.c @@ -5149,6 +5149,12 @@ cxx_eval_store_expression (const constexpr_ctx *ctx, tree t, { /* See above on initialization of empty bases. */ gcc_assert (is_empty_class (TREE_TYPE (init)) && !lval); + if (!*valp) + { + /* But do make sure we have something in *valp. */ + *valp = build_constructor (type, NULL); + CONSTRUCTOR_NO_CLEARING (*valp) = no_zero_init; + } return init; } else diff --git a/gcc/testsuite/g++.dg/cpp1y/constexpr-empty2.C b/gcc/testsuite/g++.dg/cpp1y/constexpr-empty2.C index 2acfa98364b4..9768b89904ed 100644 --- a/gcc/testsuite/g++.dg/cpp1y/constexpr-empty2.C +++ b/gcc/testsuite/g++.dg/cpp1y/constexpr-empty2.C @@ -1,4 +1,5 @@ // { dg-do compile { target c++14 } } +// { dg-additional-options -fno-elide-constructors } struct A { -- 2.47.2