Make endian_arithmetic's data member public when BOOST_ENDIAN_NO_CTORS is defined; add test

include/boost/endian/arithmetic.hpp

@@ -182,6 +182,13 @@ class endian_arithmetic
 private:
 
     typedef endian_buffer<Order, T, n_bits, Align> buffer_type;
+
+#ifdef BOOST_ENDIAN_NO_CTORS
+public:
+#else
+private:
+#endif
+
     buffer_type buf_;
 
 public:

test/Jamfile.v2

@@ -111,3 +111,4 @@ run-ni endian_reverse_test5.cpp ;
 
 run packed_buffer_test.cpp ;
 run arithmetic_buffer_test.cpp ;
+run packed_arithmetic_test.cpp ;

test/packed_arithmetic_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/arithmetic.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+using namespace boost::endian;
+
+struct X
+{
+    big_uint16_t a;
+    double b;
+    little_uint16_t c;
+} __attribute__((packed));
+
+int main()
+{
+    BOOST_TEST_EQ( sizeof( X ), 12 );
+    return boost::report_errors();
+}
+
+#endif