From 1e10b3b8825ee398f077500af6ae1f5db180983a Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Tue, 20 Aug 2024 16:52:22 +0100
Subject: [PATCH] libstdc++: Fix std::variant to reject array types [PR116381]
libstdc++-v3/ChangeLog:
PR libstdc++/116381
* include/std/variant (variant): Fix conditions for
static_assert to match the spec.
* testsuite/20_util/variant/types_neg.cc: New test.
---
libstdc++-v3/include/std/variant | 6 ++----
.../testsuite/20_util/variant/types_neg.cc | 17 +++++++++++++++++
2 files changed, 19 insertions(+), 4 deletions(-)
create mode 100644 libstdc++-v3/testsuite/20_util/variant/types_neg.cc
diff --git a/libstdc++-v3/include/std/variant b/libstdc++-v3/include/std/variant
index 12108d07f0b1..5fb7770d8891 100644
--- a/libstdc++-v3/include/std/variant
+++ b/libstdc++-v3/include/std/variant
@@ -1457,10 +1457,8 @@ namespace __detail::__variant
static_assert(sizeof...(_Types) > 0,
"variant must have at least one alternative");
- static_assert(!(std::is_reference_v<_Types> || ...),
- "variant must have no reference alternative");
- static_assert(!(std::is_void_v<_Types> || ...),
- "variant must have no void alternative");
+ static_assert(((std::is_object_v<_Types> && !is_array_v<_Types>) && ...),
+ "variant alternatives must be non-array object types");
using _Base = __detail::__variant::_Variant_base<_Types...>;
diff --git a/libstdc++-v3/testsuite/20_util/variant/types_neg.cc b/libstdc++-v3/testsuite/20_util/variant/types_neg.cc
new file mode 100644
index 000000000000..5cd3d02154b6
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/variant/types_neg.cc
@@ -0,0 +1,17 @@
+// { dg-do compile { target c++17 } }
+
+# include <variant>
+
+std::variant<> v0; // { dg-error "here" }
+// { dg-error "must have at least one alternative" "" { target *-*-* } 0 }
+std::variant<int, void> v1; // { dg-error "here" }
+std::variant<int, const void> v2; // { dg-error "here" }
+std::variant<int, int&> v3; // { dg-error "here" }
+std::variant<int, void()> v4; // { dg-error "here" }
+std::variant<int, int[]> v5; // { dg-error "here" }
+std::variant<int, int[1]> v6; // { dg-error "here" }
+// { dg-error "must be non-array object types" "" { target *-*-* } 0 }
+
+// All of variant's base classes are instantiated before checking any
+// static_assert, so we get lots of errors before the expected errors above.
+// { dg-excess-errors "" }
--
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