Constrain the primary endian_reverse to not apply to class types; add test. Fixes #41.

include/boost/endian/conversion.hpp

@@ -46,7 +46,8 @@ namespace endian
   //  reverse byte order
   //  requires T to be a non-bool integral type
   //  in detail/endian_reverse.hpp
-  template<class T> inline BOOST_CONSTEXPR T endian_reverse( T x ) BOOST_NOEXCEPT;
+  //
+  //  template<class T> inline BOOST_CONSTEXPR T endian_reverse( T x ) BOOST_NOEXCEPT;
 
   //  reverse byte order unless native endianness is big
   template <class EndianReversible >
@@ -109,8 +110,10 @@ namespace endian
 
   //  reverse in place
   //  in detail/endian_reverse.hpp
-  template <class EndianReversible>
+  //
-    inline void endian_reverse_inplace(EndianReversible& x) BOOST_NOEXCEPT;
+  //  template <class EndianReversible>
+  //    inline void endian_reverse_inplace(EndianReversible& x) BOOST_NOEXCEPT;
+  //
   //  Effects: x = endian_reverse(x)
 
   //  reverse in place unless native endianness is big

include/boost/endian/detail/endian_reverse.hpp

@@ -10,6 +10,8 @@
 #include <boost/endian/detail/intrinsic.hpp>
 #include <boost/type_traits/is_integral.hpp>
 #include <boost/type_traits/is_same.hpp>
+#include <boost/type_traits/enable_if.hpp>
+#include <boost/type_traits/is_class.hpp>
 #include <boost/static_assert.hpp>
 #include <boost/cstdint.hpp>
 #include <boost/config.hpp>
@@ -106,7 +108,9 @@ inline uint128_type BOOST_ENDIAN_CONSTEXPR endian_reverse_impl( uint128_type x )
 // Requires:
 //    T is non-bool integral
 
-template<class T> inline BOOST_CONSTEXPR T endian_reverse( T x ) BOOST_NOEXCEPT
+template<class T> inline BOOST_CONSTEXPR
+    typename enable_if_< !is_class<T>::value, T >::type
+    endian_reverse( T x ) BOOST_NOEXCEPT
 {
     BOOST_STATIC_ASSERT( is_integral<T>::value && !(is_same<T, bool>::value) );
 

test/Jamfile.v2

@@ -94,3 +94,5 @@ run endian_hpp_test.cpp ;
 run-ni endian_hpp_test.cpp ;
 
 run order_test.cpp ;
+
+run endian_reverse_test2.cpp ;

test/endian_reverse_test2.cpp

@@ -0,0 +1,39 @@
+// Copyright 2019, 2020 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// http://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/endian/conversion.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/type_traits/enable_if.hpp>
+#include <boost/type_traits/is_same.hpp>
+#include <boost/cstdint.hpp>
+
+namespace N
+{
+
+struct X
+{
+    boost::uint32_t m;
+};
+
+template<class T> typename boost::enable_if_<boost::is_same<T, X>::value, T>::type endian_reverse( T x )
+{
+    using boost::endian::endian_reverse;
+
+    X r = { endian_reverse( x.m ) };
+    return r;
+}
+
+} // namespace N
+
+int main()
+{
+    using namespace boost::endian;
+
+    N::X x1 = { 0x01020304 };
+    N::X x2 = endian_reverse( x1 );
+
+    BOOST_TEST_EQ( x2.m, 0x04030201 );
+
+    return boost::report_errors();
+}