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

doc/describe/examples.adoc

@@ -161,6 +161,18 @@ using boost::describe::operators::operator==;
 The rest of the relational operators are also provided and can
 be enabled similarly.
 
+[#example_struct_to_tuple]
+## struct_to_tuple
+
+This example defines a function `struct_to_tuple` that takes
+a described class type as an argument and returns a tuple of
+all its public members.
+
+[source]
+----
+include::../../example/struct_to_tuple.cpp[lines=5..-1]
+----
+
 [#example_to_json]
 ## Automatic Conversion to JSON
 

doc/describe/reference.adoc

@@ -88,7 +88,7 @@ enum class E: Base { v1, v2, ..., vN };
 BOOST_DESCRIBE_ENUM(E, v1, v2, ..., vN)
 ```
 
-## <boost/describe/enumerators.hpp>
+## <boost/describe/{zwsp}enumerators{zwsp}.hpp>
 
 ```
 namespace boost {
@@ -332,7 +332,7 @@ Since the library does not provide a way to describe bases and members separatel
 `has_describe_bases` and `has_describe_members` are, in practice, synonyms. They
 are provided separately for consistency.
 
-## <boost/describe/enum_to_string.hpp>
+## <boost/describe/{zwsp}enum_to_string{zwsp}.hpp>
 
 ```
 namespace boost {
@@ -349,7 +349,7 @@ The function `enum_to_string` returns the name of the enumerator `e`. `E` must
 be a described enumeration type. If `e` does not correspond to one of the described
 values, the function returns `def`.
 
-## <boost/describe/enum_from_string.hpp>
+## <boost/describe/{zwsp}enum_from_string{zwsp}.hpp>
 
 ```
 namespace boost {
@@ -440,7 +440,7 @@ Returns the negated result of `operator<`.
 Outputs a representation of `t` to `os` by recursively using `operator<<`
 to output all bases and then all members.
 
-## <boost/describe/descriptor_by_name.hpp>
+## <boost/describe/{zwsp}descriptor_by_name{zwsp}.hpp>
 
 ```
 namespace boost {
@@ -478,7 +478,7 @@ using N = BOOST_DESCRIBE_MAKE_NAME(some_member);
 using D = descriptor_by_name<L, N>; // descriptor for SomeType::some_member
 ```
 
-## <boost/describe/descriptor_by_pointer.hpp>
+## <boost/describe/{zwsp}descriptor_by_pointer{zwsp}.hpp>
 
 ```
 namespace boost {

example/struct_to_tuple.cpp

@@ -0,0 +1,55 @@
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/describe.hpp>
+#include <tuple>
+
+namespace desc = boost::describe;
+
+template<class T, template<class...> class L, class... D>
+auto struct_to_tuple_impl( T const& t, L<D...> )
+{
+    return std::make_tuple( t.*D::pointer... );
+}
+
+template<class T, class Dm = desc::describe_members<T,
+    desc::mod_public | desc::mod_inherited>>
+auto struct_to_tuple( T const& t )
+{
+    return struct_to_tuple_impl( t, Dm() );
+}
+
+#include <boost/core/type_name.hpp>
+#include <iostream>
+
+struct X
+{
+    int a = 1;
+};
+
+BOOST_DESCRIBE_STRUCT(X, (), (a))
+
+struct Y
+{
+    float b = 3.14f;
+};
+
+BOOST_DESCRIBE_STRUCT(Y, (), (b))
+
+struct Z: X, Y
+{
+};
+
+BOOST_DESCRIBE_STRUCT(Z, (X, Y), ())
+
+int main()
+{
+    Z z;
+
+    auto tp = struct_to_tuple( z );
+
+    std::cout <<
+        boost::core::type_name<decltype(tp)>() << ": "
+        << std::get<0>(tp) << ", " << std::get<1>(tp);
+}

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>>;
 

meta/libraries.json

@@ -9,6 +9,7 @@
     ],
     "description": "A C++14 reflection library.",
     "category": [
+        "Emulation",
         "Metaprogramming"
     ]
 }

test/Jamfile

@@ -63,6 +63,9 @@ run operator_lt_test.cpp ;
 run descriptor_by_name_test.cpp ;
 run descriptor_by_pointer_test.cpp ;
 
+compile unnamed_namespace_test.cpp ;
+compile unnamed_namespace_test2.cpp ;
+
 # examples
 
 obj describe_cxx14 : describe_cxx14.cpp ;
@@ -85,3 +88,4 @@ run ../example/json_rpc.cpp : : : $(CXX14) $(JSON) ;
 run ../example/hash_value.cpp : : : $(CXX14) ;
 run ../example/equality.cpp : : : $(CXX14) ;
 link ../example/console.cpp : $(CXX14) $(JSON) ;
+run ../example/struct_to_tuple.cpp : : : $(CXX14) ;

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>));
 

test/unnamed_namespace_test.cpp

@@ -0,0 +1,35 @@
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/describe.hpp>
+
+#if !defined(BOOST_DESCRIBE_CXX14)
+
+#include <boost/config/pragma_message.hpp>
+
+BOOST_PRAGMA_MESSAGE("Skipping test because C++14 is not available")
+
+#else
+
+namespace
+{
+
+enum E { v };
+
+BOOST_DESCRIBE_ENUM(E, v)
+
+struct S
+{
+};
+
+BOOST_DESCRIBE_STRUCT(S, (), ())
+
+class C
+{
+    BOOST_DESCRIBE_CLASS(C, (), (), (), ())
+};
+
+} // namespace
+
+#endif // !defined(BOOST_DESCRIBE_CXX14)

test/unnamed_namespace_test2.cpp

@@ -0,0 +1,45 @@
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/describe.hpp>
+
+#if !defined(BOOST_DESCRIBE_CXX14)
+
+#include <boost/config/pragma_message.hpp>
+
+BOOST_PRAGMA_MESSAGE("Skipping test because C++14 is not available")
+
+#else
+
+namespace
+{
+
+enum E { v };
+
+BOOST_DESCRIBE_ENUM(E, v)
+
+struct X
+{
+};
+
+BOOST_DESCRIBE_STRUCT(X, (), ())
+
+class Y
+{
+    BOOST_DESCRIBE_CLASS(Y, (), (), (), ())
+};
+
+} // namespace
+
+using namespace boost::describe;
+
+using L1 = describe_enumerators<E>;
+
+using L2 = describe_bases<X, mod_any_access>;
+using L3 = describe_members<X, mod_any_access>;
+
+using L4 = describe_bases<Y, mod_any_access>;
+using L5 = describe_members<Y, mod_any_access>;
+
+#endif // !defined(BOOST_DESCRIBE_CXX14)