In this testcase, leaving ctx->ctor pointing to the enclosing object meant
that evaluating the initializer for the subobject clobbered previous
initializers for the enclosing object. So do update ctx->ctor, just don't
add it to the enclosing object ctor.
Tested x86_64-pc-linux-gnu, applying to trunk and 12.
PR c++/105795
gcc/cp/ChangeLog:
* constexpr.cc (cxx_eval_bare_aggregate): Always call
init_subob_ctx.
gcc/testsuite/ChangeLog:
* g++.dg/cpp1z/constexpr-aggr-base1.C: New test.
---
gcc/cp/constexpr.cc | 7 ++---
.../g++.dg/cpp1z/constexpr-aggr-base1.C | 27 +++++++++++++++++++
2 files changed, 29 insertions(+), 5 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp1z/constexpr-aggr-base1.C
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 45208478c3f..021eaa34920 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -4777,12 +4777,9 @@ cxx_eval_bare_aggregate (const constexpr_ctx *ctx, tree
t,
tree orig_value = value;
/* Like in cxx_eval_store_expression, omit entries for empty fields. */
bool no_slot = TREE_CODE (type) == RECORD_TYPE && is_empty_field (index);
- if (no_slot)
- new_ctx = *ctx;
- else
- init_subob_ctx (ctx, new_ctx, index, value);
+ init_subob_ctx (ctx, new_ctx, index, value);
int pos_hint = -1;
- if (new_ctx.ctor != ctx->ctor)
+ if (new_ctx.ctor != ctx->ctor && !no_slot)
{
/* If we built a new CONSTRUCTOR, attach it now so that other
initializers can refer to it. */
diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-aggr-base1.C
b/gcc/testsuite/g++.dg/cpp1z/constexpr-aggr-base1.C
new file mode 100644
index 00000000000..06acb4a9f78
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-aggr-base1.C
@@ -0,0 +1,27 @@
+// PR c++/105795
+// { dg-do compile { target c++17 } }
+
+struct empty
+{};
+
+template <typename T>
+struct tuple_holder
+{
+ [[no_unique_address]] T value;
+};
+
+struct tuple : tuple_holder<int>, tuple_holder<empty>
+{};
+
+constexpr auto make_tuple(int&& i, empty&& e)
+{
+ return tuple{i, e};
+}
+
+constexpr int foo()
+{
+ auto tuple = make_tuple(1, empty{});
+ return static_cast<const tuple_holder<int>&>(tuple).value;
+}
+
+static_assert (foo() == 1);
base-commit: 37e4e7f77d8f7b7e911bf611a0f8edbc3a850c7a
--
2.27.0
