Change internal functions to take T** instead of T* to prevent derived to base conversions (closes #22)

Suppresses Wunused-function / Wunneeded-internal-declaration (clang) on internal-linkage types

https://github.com/boostorg/describe/issues/23

include/boost/describe/bases.hpp

@@ -21,7 +21,7 @@ namespace describe
 namespace detail
 {
 
-template<class T> using _describe_bases = decltype( boost_base_descriptor_fn( static_cast<T*>(0) ) );
+template<class T> using _describe_bases = decltype( boost_base_descriptor_fn( static_cast<T**>(0) ) );
 
 template<unsigned M> struct base_filter
 {

include/boost/describe/class.hpp

@@ -54,17 +54,17 @@ namespace describe
 #define BOOST_DESCRIBE_PRIVATE_MEMBERS_(...) BOOST_DESCRIBE_PRIVATE_MEMBERS(__VA_ARGS__)
 
 #define BOOST_DESCRIBE_CLASS(C, Bases, Public, Protected, Private) \
-    friend BOOST_DESCRIBE_BASES_(C BOOST_DESCRIBE_PP_UNPACK Bases) \
-    friend BOOST_DESCRIBE_PUBLIC_MEMBERS_(C BOOST_DESCRIBE_PP_UNPACK Public) \
-    friend BOOST_DESCRIBE_PROTECTED_MEMBERS_(C BOOST_DESCRIBE_PP_UNPACK Protected) \
-    friend BOOST_DESCRIBE_PRIVATE_MEMBERS_(C BOOST_DESCRIBE_PP_UNPACK Private)
+    BOOST_DESCRIBE_MAYBE_UNUSED friend BOOST_DESCRIBE_BASES_(C BOOST_DESCRIBE_PP_UNPACK Bases) \
+    BOOST_DESCRIBE_MAYBE_UNUSED friend BOOST_DESCRIBE_PUBLIC_MEMBERS_(C BOOST_DESCRIBE_PP_UNPACK Public) \
+    BOOST_DESCRIBE_MAYBE_UNUSED friend BOOST_DESCRIBE_PROTECTED_MEMBERS_(C BOOST_DESCRIBE_PP_UNPACK Protected) \
+    BOOST_DESCRIBE_MAYBE_UNUSED friend BOOST_DESCRIBE_PRIVATE_MEMBERS_(C BOOST_DESCRIBE_PP_UNPACK Private)
 
 #define BOOST_DESCRIBE_STRUCT(C, Bases, Members) \
     static_assert(std::is_class<C>::value, "BOOST_DESCRIBE_STRUCT should only be used with class types"); \
-    BOOST_DESCRIBE_BASES_(C BOOST_DESCRIBE_PP_UNPACK Bases) \
-    BOOST_DESCRIBE_PUBLIC_MEMBERS_(C BOOST_DESCRIBE_PP_UNPACK Members) \
-    BOOST_DESCRIBE_PROTECTED_MEMBERS_(C) \
-    BOOST_DESCRIBE_PRIVATE_MEMBERS_(C)
+    BOOST_DESCRIBE_MAYBE_UNUSED BOOST_DESCRIBE_BASES_(C BOOST_DESCRIBE_PP_UNPACK Bases) \
+    BOOST_DESCRIBE_MAYBE_UNUSED BOOST_DESCRIBE_PUBLIC_MEMBERS_(C BOOST_DESCRIBE_PP_UNPACK Members) \
+    BOOST_DESCRIBE_MAYBE_UNUSED BOOST_DESCRIBE_PROTECTED_MEMBERS_(C) \
+    BOOST_DESCRIBE_MAYBE_UNUSED BOOST_DESCRIBE_PRIVATE_MEMBERS_(C)
 
 #endif
 

include/boost/describe/detail/bases.hpp

@@ -37,12 +37,12 @@ template<class... T> auto base_descriptor_fn_impl( int, T... )
 
 #if defined(_MSC_VER) && !defined(__clang__)
 
-#define BOOST_DESCRIBE_BASES(C, ...) inline auto boost_base_descriptor_fn( C * ) \
+#define BOOST_DESCRIBE_BASES(C, ...) inline auto boost_base_descriptor_fn( C** ) \
 { return boost::describe::detail::base_descriptor_fn_impl( 0 BOOST_DESCRIBE_PP_FOR_EACH(BOOST_DESCRIBE_BASE_IMPL, C, __VA_ARGS__) ); }
 
 #else
 
-#define BOOST_DESCRIBE_BASES(C, ...) inline auto boost_base_descriptor_fn( C * ) \
+#define BOOST_DESCRIBE_BASES(C, ...) inline auto boost_base_descriptor_fn( C** ) \
 { return boost::describe::detail::base_descriptor_fn_impl( 0 BOOST_DESCRIBE_PP_FOR_EACH(BOOST_DESCRIBE_BASE_IMPL, C, ##__VA_ARGS__) ); }
 
 #endif

include/boost/describe/detail/config.hpp

@@ -27,4 +27,12 @@
 # define BOOST_DESCRIBE_CONSTEXPR_OR_CONST const
 #endif
 
+#define BOOST_DESCRIBE_MAYBE_UNUSED
+#if defined(__has_cpp_attribute)
+# if __has_cpp_attribute(maybe_unused)
+#  undef BOOST_DESCRIBE_MAYBE_UNUSED
+#  define BOOST_DESCRIBE_MAYBE_UNUSED [[maybe_unused]]
+# endif
+#endif
+
 #endif // #ifndef BOOST_DESCRIBE_DETAIL_CONFIG_HPP_INCLUDED

include/boost/describe/detail/members.hpp

@@ -53,24 +53,24 @@ template<class C, class F> constexpr auto mfn( F * p ) { return p; }
 
 #if defined(_MSC_VER) && !defined(__clang__)
 
-#define BOOST_DESCRIBE_PUBLIC_MEMBERS(C, ...) inline auto boost_public_member_descriptor_fn( C * ) \
+#define BOOST_DESCRIBE_PUBLIC_MEMBERS(C, ...) inline auto boost_public_member_descriptor_fn( C** ) \
 { return boost::describe::detail::member_descriptor_fn_impl<boost::describe::mod_public>( 0 BOOST_DESCRIBE_PP_FOR_EACH(BOOST_DESCRIBE_MEMBER_IMPL, C, __VA_ARGS__) ); }
 
-#define BOOST_DESCRIBE_PROTECTED_MEMBERS(C, ...) inline auto boost_protected_member_descriptor_fn( C * ) \
+#define BOOST_DESCRIBE_PROTECTED_MEMBERS(C, ...) inline auto boost_protected_member_descriptor_fn( C** ) \
 { return boost::describe::detail::member_descriptor_fn_impl<boost::describe::mod_protected>( 0 BOOST_DESCRIBE_PP_FOR_EACH(BOOST_DESCRIBE_MEMBER_IMPL, C, __VA_ARGS__) ); }
 
-#define BOOST_DESCRIBE_PRIVATE_MEMBERS(C, ...) inline auto boost_private_member_descriptor_fn( C * ) \
+#define BOOST_DESCRIBE_PRIVATE_MEMBERS(C, ...) inline auto boost_private_member_descriptor_fn( C** ) \
 { return boost::describe::detail::member_descriptor_fn_impl<boost::describe::mod_private>( 0 BOOST_DESCRIBE_PP_FOR_EACH(BOOST_DESCRIBE_MEMBER_IMPL, C, __VA_ARGS__) ); }
 
 #else
 
-#define BOOST_DESCRIBE_PUBLIC_MEMBERS(C, ...) inline auto boost_public_member_descriptor_fn( C * ) \
+#define BOOST_DESCRIBE_PUBLIC_MEMBERS(C, ...) inline auto boost_public_member_descriptor_fn( C** ) \
 { return boost::describe::detail::member_descriptor_fn_impl<boost::describe::mod_public>( 0 BOOST_DESCRIBE_PP_FOR_EACH(BOOST_DESCRIBE_MEMBER_IMPL, C, ##__VA_ARGS__) ); }
 
-#define BOOST_DESCRIBE_PROTECTED_MEMBERS(C, ...) inline auto boost_protected_member_descriptor_fn( C * ) \
+#define BOOST_DESCRIBE_PROTECTED_MEMBERS(C, ...) inline auto boost_protected_member_descriptor_fn( C** ) \
 { return boost::describe::detail::member_descriptor_fn_impl<boost::describe::mod_protected>( 0 BOOST_DESCRIBE_PP_FOR_EACH(BOOST_DESCRIBE_MEMBER_IMPL, C, ##__VA_ARGS__) ); }
 
-#define BOOST_DESCRIBE_PRIVATE_MEMBERS(C, ...) inline auto boost_private_member_descriptor_fn( C * ) \
+#define BOOST_DESCRIBE_PRIVATE_MEMBERS(C, ...) inline auto boost_private_member_descriptor_fn( C** ) \
 { return boost::describe::detail::member_descriptor_fn_impl<boost::describe::mod_private>( 0 BOOST_DESCRIBE_PP_FOR_EACH(BOOST_DESCRIBE_MEMBER_IMPL, C, ##__VA_ARGS__) ); }
 
 #endif

include/boost/describe/enum.hpp

@@ -42,7 +42,7 @@ template<class... T> auto enum_descriptor_fn_impl( int, T... )
 }
 
 #define BOOST_DESCRIBE_ENUM_BEGIN(E) \
-    inline auto boost_enum_descriptor_fn( E* ) \
+    inline auto boost_enum_descriptor_fn( E** ) \
     { return boost::describe::detail::enum_descriptor_fn_impl( 0
 
 #define BOOST_DESCRIBE_ENUM_ENTRY(E, e) , []{ struct _boost_desc { \
@@ -71,13 +71,13 @@ template<class... T> auto enum_descriptor_fn_impl( int, T... )
 
 #define BOOST_DESCRIBE_ENUM(E, ...) \
     static_assert(std::is_enum<E>::value, "BOOST_DESCRIBE_ENUM should only be used with enums"); \
-    BOOST_DESCRIBE_ENUM_BEGIN(E) \
+    BOOST_DESCRIBE_MAYBE_UNUSED BOOST_DESCRIBE_ENUM_BEGIN(E) \
     BOOST_DESCRIBE_PP_FOR_EACH(BOOST_DESCRIBE_ENUM_ENTRY, E, ##__VA_ARGS__) \
     BOOST_DESCRIBE_ENUM_END(E)
 
 #define BOOST_DESCRIBE_NESTED_ENUM(E, ...) \
     static_assert(std::is_enum<E>::value, "BOOST_DESCRIBE_NESTED_ENUM should only be used with enums"); \
-    friend BOOST_DESCRIBE_ENUM_BEGIN(E) \
+    BOOST_DESCRIBE_MAYBE_UNUSED friend BOOST_DESCRIBE_ENUM_BEGIN(E) \
     BOOST_DESCRIBE_PP_FOR_EACH(BOOST_DESCRIBE_ENUM_ENTRY, E, ##__VA_ARGS__) \
     BOOST_DESCRIBE_ENUM_END(E)
 

include/boost/describe/enumerators.hpp

@@ -19,7 +19,7 @@ namespace describe
 
 // describe_enumerators<E>
 
-template<class E> using describe_enumerators = decltype( boost_enum_descriptor_fn( static_cast<E*>(0) ) );
+template<class E> using describe_enumerators = decltype( boost_enum_descriptor_fn( static_cast<E**>(0) ) );
 
 // has_describe_enumerators<E>
 

include/boost/describe/members.hpp

@@ -29,9 +29,9 @@ namespace detail
 
 // _describe_members<T>
 
-template<class T> using _describe_public_members = decltype( boost_public_member_descriptor_fn( static_cast<T*>(0) ) );
-template<class T> using _describe_protected_members = decltype( boost_protected_member_descriptor_fn( static_cast<T*>(0) ) );
-template<class T> using _describe_private_members = decltype( boost_private_member_descriptor_fn( static_cast<T*>(0) ) );
+template<class T> using _describe_public_members = decltype( boost_public_member_descriptor_fn( static_cast<T**>(0) ) );
+template<class T> using _describe_protected_members = decltype( boost_protected_member_descriptor_fn( static_cast<T**>(0) ) );
+template<class T> using _describe_private_members = decltype( boost_private_member_descriptor_fn( static_cast<T**>(0) ) );
 
 template<class T> using _describe_members = mp11::mp_append<_describe_public_members<T>, _describe_protected_members<T>, _describe_private_members<T>>;
 

test/has_bases_test.cpp

@@ -27,6 +27,9 @@ struct X3 {};
 class X4 {};
 union X5 {};
 
+struct X6: X1 {};
+struct X7: X2 {};
+
 int main()
 {
     using boost::describe::has_describe_bases;
@@ -46,6 +49,8 @@ int main()
     BOOST_TEST_TRAIT_FALSE((has_describe_bases<X3>));
     BOOST_TEST_TRAIT_FALSE((has_describe_bases<X4>));
     BOOST_TEST_TRAIT_FALSE((has_describe_bases<X5>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_bases<X6>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_bases<X7>));
     BOOST_TEST_TRAIT_FALSE((has_describe_bases<int>));
     BOOST_TEST_TRAIT_FALSE((has_describe_bases<void>));
 

test/has_members_test.cpp

@@ -27,6 +27,9 @@ struct X3 {};
 class X4 {};
 union X5 {};
 
+struct X6: X1 {};
+struct X7: X2 {};
+
 int main()
 {
     using boost::describe::has_describe_members;
@@ -46,6 +49,8 @@ int main()
     BOOST_TEST_TRAIT_FALSE((has_describe_members<X3>));
     BOOST_TEST_TRAIT_FALSE((has_describe_members<X4>));
     BOOST_TEST_TRAIT_FALSE((has_describe_members<X5>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_members<X6>));
+    BOOST_TEST_TRAIT_FALSE((has_describe_members<X7>));
     BOOST_TEST_TRAIT_FALSE((has_describe_members<int>));
     BOOST_TEST_TRAIT_FALSE((has_describe_members<void>));