Fix for 'Arrays of Length Zero' compiler extension (#213)

test/core/run/zero_size_array.cpp

@@ -0,0 +1,33 @@
+// Copyright (c) 2025-2025 Antony Polukhin
+//
+// Distributed under the Boost Software License, Version 1.0. (See accompanying
+// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+
+// Test that PFR works with GCCs "Arrays of Length Zero" extension
+
+#include <boost/pfr/core.hpp>
+
+#include <tuple>
+
+#if defined(__GNUC__) && (BOOST_PFR_USE_LOOPHOLE || BOOST_PFR_USE_CPP17)
+struct zero_array {
+    char data[0];
+};
+
+struct aggr {
+    zero_array a;
+};
+
+static_assert(sizeof(zero_array) == 0);
+static_assert(sizeof(aggr) == 0);
+
+int main() {
+    aggr a;
+    const auto result = boost::pfr::structure_tie(a);
+    static_assert(std::tuple_size<decltype(result)>::value == 1);
+    return sizeof(std::get<0>(result).data);
+}
+#else
+int main() {}
+#endif
+