Make endian_buffer::value_ public when BOOST_ENDIAN_NO_CTORS is defined; add test

include/boost/endian/buffers.hpp

@@ -218,7 +218,9 @@ namespace endian
 template< BOOST_SCOPED_ENUM(order) Order, class T, std::size_t n_bits >
 class endian_buffer<Order, T, n_bits, align::no>
 {
-private:
+#ifdef BOOST_ENDIAN_NO_CTORS
+public:
+#endif
 
     BOOST_STATIC_ASSERT( (n_bits/8)*8 == n_bits );
 

test/Jamfile.v2

@@ -108,3 +108,5 @@ run-ni endian_reverse_test4.cpp ;
 
 run endian_reverse_test5.cpp ;
 run-ni endian_reverse_test5.cpp ;
+
+run packed_buffer_test.cpp ;

test/packed_buffer_test.cpp

@@ -0,0 +1,33 @@
+// Copyright 2020 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#if !defined(__GNUC__)
+
+#include <boost/config/pragma_message.hpp>
+BOOST_PRAGMA_MESSAGE( "Skipping test because __GNUC__ is not defined" )
+int main() {}
+
+#else
+
+#define BOOST_ENDIAN_FORCE_PODNESS
+#define BOOST_ENDIAN_NO_CTORS
+#include <boost/endian/buffers.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+using namespace boost::endian;
+
+struct X
+{
+    big_uint16_buf_t a;
+    double b;
+    little_uint16_buf_t c;
+} __attribute__((packed));
+
+int main()
+{
+    BOOST_TEST_EQ( sizeof( X ), 12 );
+    return boost::report_errors();
+}
+
+#endif