From 68db6ebd2d4813bd5dbf5e9e1c57424fdd003fde Mon Sep 17 00:00:00 2001
From: Peter Dimov <pdimov@gmail.com>
Date: Mon, 27 Jan 2025 03:59:32 +0200
Subject: [PATCH] Add operator<=> overload for zero-sized arrays

---
 include/boost/array.hpp | 7 +++++++
 test/array_thw_test.cpp | 4 ++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/include/boost/array.hpp b/include/boost/array.hpp
index 995a888..d1a7a2b 100644
--- a/include/boost/array.hpp
+++ b/include/boost/array.hpp
@@ -396,6 +396,13 @@ namespace boost {
         return 0 <=> 0; // std::strong_ordering::equal
     }
 
+    template<class T>
+    constexpr auto operator<=> (const array<T,0>& x, const array<T,0>& y)
+        -> decltype( 0 <=> 0 )
+    {
+        return 0 <=> 0; // std::strong_ordering::equal
+    }
+
 #endif
 
     // undocumented and obsolete
diff --git a/test/array_thw_test.cpp b/test/array_thw_test.cpp
index 3376e36..8f10368 100644
--- a/test/array_thw_test.cpp
+++ b/test/array_thw_test.cpp
@@ -77,11 +77,11 @@ template<class T, std::size_t N> void test()
 
 int main()
 {
-    // test<int, 0>();
+    test<int, 0>();
     test<int, 1>();
     test<int, 7>();
 
-    // test<float, 0>();
+    test<float, 0>();
     test<float, 1>();
     test<float, 7>();