Add examples/point2.cpp

.drone.jsonnet

@@ -135,47 +135,205 @@ local windows_pipeline(name, image, environment, arch = "amd64") =
     ),
 
     linux_pipeline(
-        "Linux 20.04 GCC 9 ARM64",
+        "Linux 16.04 GCC 5* 32/64",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14', ADDRMD: '32,64' },
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 GCC 6 32/64",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-6', CXXSTD: '03,11,14', ADDRMD: '32,64' },
+        "g++-6-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 GCC 7* 32/64",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17', ADDRMD: '32,64' },
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 GCC 8 32/64",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-8', CXXSTD: '03,11,14,17', ADDRMD: '32,64' },
+        "g++-8-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9* 32/64",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a', ADDRMD: '32,64' },
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9* ARM64",
         "cppalliance/droneubuntu2004:multiarch",
         { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a' },
         arch="arm64",
     ),
 
     linux_pipeline(
-        "Linux 20.04 GCC 9 S390x",
+        "Linux 20.04 GCC 9* S390x",
         "cppalliance/droneubuntu2004:multiarch",
         { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a' },
         arch="s390x",
     ),
 
+    linux_pipeline(
+        "Linux 20.04 GCC 10 32/64",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-10', CXXSTD: '03,11,14,17,20', ADDRMD: '32,64' },
+        "g++-10-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 11* 32/64",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a', ADDRMD: '32,64' },
+    ),
+
     linux_pipeline(
         "Linux 22.04 GCC 12 32 ASAN",
         "cppalliance/droneubuntu2204:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '03,11,14,17,20', ADDRMD: '32' } + asan,
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '03,11,14,17,20,2b', ADDRMD: '32' } + asan,
         "g++-12-multilib",
     ),
 
     linux_pipeline(
         "Linux 22.04 GCC 12 64 ASAN",
         "cppalliance/droneubuntu2204:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '03,11,14,17,20', ADDRMD: '64' } + asan,
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '03,11,14,17,20,2b', ADDRMD: '64' } + asan,
         "g++-12-multilib",
     ),
 
+    linux_pipeline(
+        "Linux 16.04 Clang 3.5",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.5', CXXSTD: '03,11' },
+        "clang-3.5",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 Clang 3.6",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.6', CXXSTD: '03,11,14' },
+        "clang-3.6",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 Clang 3.7",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.7', CXXSTD: '03,11,14' },
+        "clang-3.7",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 Clang 3.8",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.8', CXXSTD: '03,11,14' },
+        "clang-3.8",
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 Clang 3.9",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.9', CXXSTD: '03,11,14' },
+        "clang-3.9",
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 Clang 4.0",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-4.0', CXXSTD: '03,11,14' },
+        "clang-4.0",
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 Clang 5.0",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-5.0', CXXSTD: '03,11,14,1z' },
+        "clang-5.0",
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 Clang 6.0",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-6.0', CXXSTD: '03,11,14,17' },
+        "clang-6.0",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 7",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-7', CXXSTD: '03,11,14,17' },
+        "clang-7",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 8",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-8', CXXSTD: '03,11,14,17' },
+        "clang-8",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 9",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-9', CXXSTD: '03,11,14,17,2a' },
+        "clang-9",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 10",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-10', CXXSTD: '03,11,14,17,2a' },
+        "clang-10",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 11",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-11', CXXSTD: '03,11,14,17,2a' },
+        "clang-11",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 12",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-12', CXXSTD: '03,11,14,17,2a' },
+        "clang-12",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 Clang 13",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-13', CXXSTD: '03,11,14,17,20' },
+        "clang-13",
+    ),
+
     linux_pipeline(
         "Linux 22.04 Clang 14 UBSAN",
         "cppalliance/droneubuntu2204:1",
-        { TOOLSET: 'clang', COMPILER: 'clang++-14', CXXSTD: '03,11,14,17,20' } + ubsan,
+        { TOOLSET: 'clang', COMPILER: 'clang++-14', CXXSTD: '03,11,14,17,20,2b' } + ubsan,
         "clang-14",
     ),
 
     linux_pipeline(
         "Linux 22.04 Clang 14 ASAN",
         "cppalliance/droneubuntu2204:1",
-        { TOOLSET: 'clang', COMPILER: 'clang++-14', CXXSTD: '03,11,14,17,20' } + asan,
+        { TOOLSET: 'clang', COMPILER: 'clang++-14', CXXSTD: '03,11,14,17,20,2b' } + asan,
         "clang-14",
     ),
 
+    linux_pipeline(
+        "Linux 22.04 Clang 15",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-15', CXXSTD: '03,11,14,17,20,2b' },
+        "clang-15",
+        ["deb http://apt.llvm.org/jammy/ llvm-toolchain-jammy-15 main"],
+    ),
+
     macos_pipeline(
         "MacOS 10.15 Xcode 12.2 UBSAN",
         { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '03,11,14,1z' } + ubsan,
@@ -186,9 +344,27 @@ local windows_pipeline(name, image, environment, arch = "amd64") =
         { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '03,11,14,1z' } + asan,
     ),
 
+    windows_pipeline(
+        "Windows VS2015 msvc-14.0",
+        "cppalliance/dronevs2015",
+        { TOOLSET: 'msvc-14.0', CXXSTD: '14,latest' },
+    ),
+
     windows_pipeline(
         "Windows VS2017 msvc-14.1",
         "cppalliance/dronevs2017",
         { TOOLSET: 'msvc-14.1', CXXSTD: '14,17,latest' },
     ),
+
+    windows_pipeline(
+        "Windows VS2019 msvc-14.2",
+        "cppalliance/dronevs2019",
+        { TOOLSET: 'msvc-14.2', CXXSTD: '14,17,20,latest' },
+    ),
+
+    windows_pipeline(
+        "Windows VS2022 msvc-14.3",
+        "cppalliance/dronevs2022:1",
+        { TOOLSET: 'msvc-14.3', CXXSTD: '14,17,20,latest' },
+    ),
 ]

.github/workflows/ci.yml

@@ -126,7 +126,7 @@ jobs:
     runs-on: ${{matrix.os}}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Install packages
         if: matrix.install
@@ -195,7 +195,7 @@ jobs:
     runs-on: ${{matrix.os}}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Setup Boost
         shell: cmd
@@ -239,7 +239,7 @@ jobs:
     runs-on: ${{matrix.os}}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Install packages
         if: matrix.install
@@ -286,7 +286,7 @@ jobs:
     runs-on: ${{matrix.os}}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Install packages
         if: matrix.install
@@ -343,7 +343,7 @@ jobs:
     runs-on: ${{matrix.os}}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Install packages
         if: matrix.install

CMakeLists.txt

@@ -15,6 +15,8 @@ target_include_directories(boost_container_hash INTERFACE include)
 target_link_libraries(boost_container_hash
   INTERFACE
     Boost::config
+    Boost::describe
+    Boost::mp11
     Boost::type_traits
 )
 

README.md

@@ -0,0 +1,20 @@
+# Boost.ContainerHash
+
+The Boost.ContainerHash library, part of [Boost C++ Libraries](https://boost.org),
+provides `boost::hash`, an enhanced implementation of the
+[hash function](https://en.wikipedia.org/wiki/Hash_function) object specified
+by C++11 as `std::hash`, and several support facilities (`hash_combine`,
+`hash_range`, `hash_unordered_range`).
+
+`boost::hash` supports most standard types and some user-defined types out of
+the box, and is extensible; it's possible for a user-defined type `X` to make
+iself hashable via `boost::hash<X>` by defining an appropriate overload of the
+function `hash_value`.
+
+See [the documentation of the library](https://www.boost.org/libs/container_hash)
+for more information.
+
+## License
+
+Distributed under the
+[Boost Software License, Version 1.0](http://boost.org/LICENSE_1_0.txt).

doc/hash.adoc

@@ -22,6 +22,7 @@ include::hash/recent.adoc[]
 include::hash/tutorial.adoc[]
 include::hash/user.adoc[]
 include::hash/combine.adoc[]
+include::hash/describe.adoc[]
 include::hash/reference.adoc[]
 include::hash/notes.adoc[]
 include::hash/links.adoc[]

doc/hash/describe.adoc

@@ -0,0 +1,61 @@
+////
+Copyright 2022 Peter Dimov
+Distributed under the Boost Software License, Version 1.0.
+https://www.boost.org/LICENSE_1_0.txt
+////
+
+[#describe]
+= Hashing User Types with Boost.Describe
+:idprefix: describe_
+
+Let's look at our `point` class again:
+
+[source]
+----
+class point
+{
+    int x;
+    int y;
+
+public:
+
+    point() : x(0), y(0) {}
+    point(int x, int y) : x(x), y(y) {}
+};
+----
+
+If you're using {cpp}14 or above, a much easier way to add
+support for `boost::hash` to `point` is by using
+link:../../../describe/index.html[Boost.Describe] (and
+get an automatic definition of `operator==` for free):
+
+[source]
+----
+
+#include <boost/describe/class.hpp>
+#include <boost/describe/operators.hpp>
+
+class point
+{
+    int x;
+    int y;
+
+    BOOST_DESCRIBE_CLASS(point, (), (), (), (x, y))
+
+public:
+
+    point() : x(0), y(0) {}
+    point(int x, int y) : x(x), y(y) {}
+};
+
+using boost::describe::operators::operator==;
+using boost::describe::operators::operator!=;
+----
+
+(Full code for this example is at
+link:../../examples/point2.cpp[examples/point2.cpp].)
+
+Since the `point` class has been annotated with `BOOST_DESCRIBE_CLASS`,
+the library can enumerate its members (and base classes) and automatically
+synthesize the appropriate `hash_value` overload for it, without us needing
+to do so.

doc/hash/intro.adoc

@@ -32,6 +32,9 @@ Out of the box, `boost::hash` supports
 * unordered sequences, standard or user-defined (sequences for which the hash
   value does not depend on the element order, such as `std::unordered_set` and
   `std::unordered_map`);
+* described structs and classes -- ones that have been annotated with the
+  `BOOST_DESCRIBE_STRUCT` or `BOOST_DESCRIBE_CLASS` macros from
+  link:../../../describe/index.html[Boost.Describe];
 * `std::unique_ptr`, `std::shared_ptr`;
 * `std::type_index`;
 * `std::error_code`, `std::error_condition`;

doc/hash/notes.adoc

@@ -10,6 +10,26 @@ https://www.boost.org/LICENSE_1_0.txt
 = Design and Implementation Notes
 :idprefix: notes_
 
+== Quality of the Hash Function
+
+Many hash functions strive to have little correlation between the input and
+output values. They attempt to uniformally distribute the output values for
+very similar inputs. This hash function makes no such attempt. In fact, for
+integers, the result of the hash function is often just the input value. So
+similar but different input values will often result in similar but different
+output values. This means that it is not appropriate as a general hash
+function. For example, a hash table may discard bits from the hash function
+resulting in likely collisions, or might have poor collision resolution when
+hash values are clustered together. In such cases this hash function will
+perform poorly.
+
+But the standard has no such requirement for the hash function, it just
+requires that the hashes of two different values are unlikely to collide.
+Containers or algorithms designed to work with the standard hash function will
+have to be implemented to work well when the hash function's output is
+correlated to its input. Since they are paying that cost a higher quality hash
+function would be wasteful.
+
 == The hash_value Customization Point
 
 The way one customizes the standard `std::hash` function object for user
@@ -154,22 +174,46 @@ With this improved `hash_combine`, `boost::hash` for strings now passes the
 https://github.com/aappleby/smhasher[SMHasher test suite] by Austin Appleby
 (for a 64 bit `size_t`).
 
-== Quality of the Hash Function
+== hash_range
 
-Many hash functions strive to have little correlation between the input and
-output values. They attempt to uniformally distribute the output values for
-very similar inputs. This hash function makes no such attempt. In fact, for
-integers, the result of the hash function is often just the input value. So
-similar but different input values will often result in similar but different
-output values. This means that it is not appropriate as a general hash
-function. For example, a hash table may discard bits from the hash function
-resulting in likely collisions, or might have poor collision resolution when
-hash values are clustered together. In such cases this hash function will
-perform poorly.
+The traditional implementation of `hash_range(seed, first, last)` has been
 
-But the standard has no such requirement for the hash function, it just
-requires that the hashes of two different values are unlikely to collide.
-Containers or algorithms designed to work with the standard hash function will
-have to be implemented to work well when the hash function's output is
-correlated to its input. Since they are paying that cost a higher quality hash
-function would be wasteful.
+[source]
+----
+for( ; first != last; ++first )
+{
+    boost::hash_combine<typename std::iterator_traits<It>::value_type>( seed, *first );
+}
+----
+
+(the explicit template parameter is needed to support iterators with proxy
+return types such as `std::vector<bool>::iterator`.)
+
+This is logical, consistent and straightforward. In the common case where
+`typename std::iterator_traits<It>::value_type` is `char` -- which it is
+in the common case of `boost::hash<std::string>` -- this however leaves a
+lot of performance on the table, because processing each `char` individually
+is much less efficient than processing several in bulk.
+
+In Boost 1.81, `hash_range` was changed to process elements of type `char`,
+`signed char`, `unsigned char`, `std::byte`, or `char8_t`, four of a time.
+A `uint32_t` is composed from `first[0]` to `first[3]`, and that `uint32_t`
+is fed to `hash_combine`.
+
+In principle, when `size_t` is 64 bit, we could have used `uint64_t` instead.
+We do not, because this allows producing an arbitrary hash value by choosing
+the input bytes appropriately (because `hash_combine` is reversible.)
+
+Allowing control only over 32 bits of the full 64 bit `size_t` value makes
+these "chosen plaintext attacks" harder.
+
+This is not as harmful to performance as it first appears, because the
+input to `hash<string>` (e.g. the key in an unordered container) is often
+short (9 to 13 bytes in some typical scenarios.)
+
+Note that `hash_range` has also traditionally guaranteed that the same element
+sequence yields the same hash value regardless of the iterator type. This
+property remains valid after the changes to `char` range hashing. `hash_range`,
+applied to the `char` sequence `{ 'a', 'b', 'c' }`, results in the same value
+whether the sequence comes from `char[3]`, `std::string`, `std::deque<char>`,
+or `std::list<char>`.

doc/hash/recent.adoc

@@ -21,6 +21,9 @@ Major update.
 * User-defined containers (types that have `begin()` and `end()`
   member functions that return iterators) are now supported out
   of the box.
+* Described structs and classes (those annotated with
+  `BOOST_DESCRIBE_STRUCT` or `BOOST_DESCRIBE_CLASS`) are now
+  supported out of the box.
 * `hash_combine` has been improved.
 * The performance (and quality, as a result of the above change)
   of string hashing has been improved. `boost::hash` for strings

doc/hash/reference.adoc

@@ -29,6 +29,7 @@ namespace container_hash
 template<class T> struct is_range;
 template<class T> struct is_contiguous_range;
 template<class T> struct is_unordered_range;
+template<class T> struct is_described_class;
 
 } // namespace container_hash
 
@@ -103,6 +104,10 @@ template<class T>
 template<class T>
   std::size_t hash_value( T const& v );
 
+// Enabled only when container_hash::is_described_class<T>::value is true
+template<class T>
+  std::size_t hash_value( T const& v );
+
 template<class T>
   std::size_t hash_value( std::shared_ptr<T> const& v );
 
@@ -225,7 +230,7 @@ Effects: ::
 +
 --
 When `typename std::iterator_traits<It>::value_type` is not `char`, `signed char`,
-`unsigned char`,
+`unsigned char`, `std::byte`, or `char8_t`,
 
 [source]
 ----
@@ -446,6 +451,34 @@ Remarks: ::
 This overload handles the standard unordered containers, such as
 `std::unordered_set` and `std::unordered_map`.
 
+[source]
+----
+// Enabled only when container_hash::is_described_class<T>::value is true
+template<class T>
+  std::size_t hash_value( T const& v );
+----
+
+Effects: ::
++
+[source]
+----
+std::size_t seed = 0;
+
+boost::hash_combine( seed, b1 );
+boost::hash_combine( seed, b2 );
+// ...
+boost::hash_combine( seed, bM );
+
+boost::hash_combine( seed, m1 );
+boost::hash_combine( seed, m2 );
+// ...
+boost::hash_combine( seed, mN );
+
+return seed;
+----
++
+where `bi` are the bases of `v` and `mi` are its members.
+
 [source]
 ----
 template<class T>
@@ -633,3 +666,40 @@ template<class T> struct is_unordered_range
 
 Users are allowed to specialize `is_unordered_range` for their types
 if the default behavior does not deduce the correct value.
+
+== <boost/container_hash/{zwsp}is_described_class.hpp>
+
+Defines the trait `boost::container_hash::is_described_class`.
+
+[source]
+----
+namespace boost
+{
+
+namespace container_hash
+{
+
+template<class T> struct is_described_class;
+
+} // namespace container_hash
+
+} // namespace boost
+----
+
+=== is_described_class<T>
+
+[source]
+----
+template<class T> struct is_described_class
+{
+    static constexpr bool value = /* see below */;
+};
+----
+
+`is_described_class<T>::value` is `true` when
+`boost::describe::has_describe_bases<T>::value` is `true`,
+`boost::describe::has_describe_members<T>::value` is `true`, and
+`T` is not a union.
+
+Users are allowed to specialize `is_described_class` for their types
+if the default behavior does not deduce the correct value.

doc/hash/thanks.adoc

@@ -1,6 +1,13 @@
+////
+Copyright 2005-2008 Daniel James
+Copyright 2022 Christian Mazakas
+Copyright 2022 Peter Dimov
+Distributed under the Boost Software License, Version 1.0.
+https://www.boost.org/LICENSE_1_0.txt
+////
+
 [#thanks]
 = Acknowledgements
-
 :idprefix: thanks_
 
 This library is based on the design by Peter Dimov. During the initial development Joaquín M López Muñoz made many useful suggestions and contributed fixes.
@@ -12,3 +19,5 @@ The implementation of the hash function for pointers is based on suggestions mad
 Some useful improvements to the floating point hash algorithm were suggested by Daniel Krügler.
 
 The original implementation came from Jeremy B. Maitin-Shepard's hash table library, although this is a complete rewrite.
+
+The documentation was converted from Quickbook to AsciiDoc by Christian Mazakas.

doc/hash/user.adoc

@@ -74,7 +74,7 @@ assert(books.find(knife) != books.end());
 assert(books.find(dandelion) == books.end());
 ----
 
-The full example can be found in:
+The full example can be found in
 link:../../examples/books.hpp[examples/books.hpp] and
 link:../../examples/books.cpp[examples/books.cpp].
 

examples/Jamfile.v2

@@ -7,3 +7,4 @@ run books.cpp ;
 run point.cpp ;
 run portable.cpp ;
 run template.cpp : : : <toolset>msvc-8.0:<build>no ;
+run point2.cpp ;

examples/point2.cpp

@@ -0,0 +1,65 @@
+
+// Copyright 2005 Daniel James.
+// Copyright 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+// Force use of assert.
+#if defined(NDEBUG)
+#undef NDEBUG
+#endif
+
+#include <boost/container_hash/hash.hpp>
+#include <boost/describe/class.hpp>
+#include <boost/describe/operators.hpp>
+#include <cassert>
+
+// This example illustrates how to use Boost.Describe to obtain
+// automatic boost::hash support. For full details see the hash
+// tutorial.
+
+#if defined(BOOST_DESCRIBE_CXX14)
+
+class point
+{
+    int x;
+    int y;
+
+    BOOST_DESCRIBE_CLASS(point, (), (), (), (x, y))
+
+public:
+
+    point() : x(0), y(0) {}
+    point(int x, int y) : x(x), y(y) {}
+};
+
+using boost::describe::operators::operator==;
+using boost::describe::operators::operator!=;
+
+int main()
+{
+    boost::hash<point> point_hasher;
+
+    point p1(0, 0);
+    point p2(1, 2);
+    point p3(4, 1);
+    point p4 = p1;
+
+    assert(point_hasher(p1) == point_hasher(p4));
+
+    // These tests could legally fail, but if they did it'd be a pretty bad
+    // hash function.
+    assert(point_hasher(p1) != point_hasher(p2));
+    assert(point_hasher(p1) != point_hasher(p3));
+}
+
+#else
+
+#include <cstdio>
+
+int main()
+{
+    std::puts( "This example requires C++14." );
+}
+
+#endif

include/boost/container_hash/detail/hash_range.hpp

@@ -27,6 +27,14 @@ template<> struct is_char_type<char>: public boost::true_type {};
 template<> struct is_char_type<signed char>: public boost::true_type {};
 template<> struct is_char_type<unsigned char>: public boost::true_type {};
 
+#if defined(__cpp_char8_t) && __cpp_char8_t >= 201811L
+template<> struct is_char_type<char8_t>: public boost::true_type {};
+#endif
+
+#if defined(__cpp_lib_byte) && __cpp_lib_byte >= 201603L
+template<> struct is_char_type<std::byte>: public boost::true_type {};
+#endif
+
 #endif
 
 template<class It>

include/boost/container_hash/hash.hpp

@@ -14,6 +14,7 @@
 #include <boost/container_hash/is_range.hpp>
 #include <boost/container_hash/is_contiguous_range.hpp>
 #include <boost/container_hash/is_unordered_range.hpp>
+#include <boost/container_hash/is_described_class.hpp>
 #include <boost/container_hash/detail/hash_tuple.hpp>
 #include <boost/container_hash/detail/hash_mix.hpp>
 #include <boost/container_hash/detail/hash_range.hpp>
@@ -25,7 +26,15 @@
 #include <boost/type_traits/make_unsigned.hpp>
 #include <boost/type_traits/enable_if.hpp>
 #include <boost/type_traits/conjunction.hpp>
+#include <boost/type_traits/is_union.hpp>
+#include <boost/describe/bases.hpp>
+#include <boost/describe/members.hpp>
 #include <boost/cstdint.hpp>
+
+#if defined(BOOST_DESCRIBE_CXX14)
+# include <boost/mp11/algorithm.hpp>
+#endif
+
 #include <string>
 #include <iterator>
 #include <complex>
@@ -54,6 +63,10 @@
 #include <variant>
 #endif
 
+#if !defined(BOOST_NO_CXX17_HDR_STRING_VIEW)
+# include <string_view>
+#endif
+
 namespace boost
 {
 
@@ -383,6 +396,49 @@ namespace boost
         return boost::hash_unordered_range( v.begin(), v.end() );
     }
 
+#endif
+
+    // described classes
+
+#if defined(BOOST_DESCRIBE_CXX14)
+
+#if defined(_MSC_VER) && _MSC_VER == 1900
+# pragma warning(push)
+# pragma warning(disable: 4100) // unreferenced formal parameter
+#endif
+
+    template <typename T>
+    typename boost::enable_if_<container_hash::is_described_class<T>::value, std::size_t>::type
+        hash_value( T const& v )
+    {
+        static_assert( !boost::is_union<T>::value, "described unions are not supported" );
+
+        std::size_t r = 0;
+
+        using Bd = describe::describe_bases<T, describe::mod_any_access>;
+
+        mp11::mp_for_each<Bd>([&](auto D){
+
+            using B = typename decltype(D)::type;
+            boost::hash_combine( r, (B const&)v );
+
+        });
+
+        using Md = describe::describe_members<T, describe::mod_any_access>;
+
+        mp11::mp_for_each<Md>([&](auto D){
+
+            boost::hash_combine( r, v.*D.pointer );
+
+        });
+
+        return r;
+    }
+
+#if defined(_MSC_VER) && _MSC_VER == 1900
+# pragma warning(pop)
+#endif
+
 #endif
 
     // std::unique_ptr, std::shared_ptr
@@ -577,6 +633,30 @@ namespace boost
     };
 
 #endif
-}
+
+    // boost::unordered::hash_is_avalanching
+
+    namespace unordered
+    {
+        template<class T> struct hash_is_avalanching;
+        template<class Ch> struct hash_is_avalanching< boost::hash< std::basic_string<Ch> > >: boost::is_integral<Ch> {};
+
+        // boost::is_integral<char8_t> is false, but should be true (https://github.com/boostorg/type_traits/issues/175)
+#if defined(__cpp_char8_t) && __cpp_char8_t >= 201811L
+        template<> struct hash_is_avalanching< boost::hash< std::basic_string<char8_t> > >: boost::true_type {};
+#endif
+
+#if !defined(BOOST_NO_CXX17_HDR_STRING_VIEW)
+
+        template<class Ch> struct hash_is_avalanching< boost::hash< std::basic_string_view<Ch> > >: boost::is_integral<Ch> {};
+
+#if defined(__cpp_char8_t) && __cpp_char8_t >= 201811L
+        template<> struct hash_is_avalanching< boost::hash< std::basic_string_view<char8_t> > >: boost::true_type {};
+#endif
+
+#endif
+    } // namespace unordered
+
+} // namespace boost
 
 #endif // #ifndef BOOST_FUNCTIONAL_HASH_HASH_HPP

include/boost/container_hash/hash_fwd.hpp

@@ -1,5 +1,5 @@
 // Copyright 2005-2009 Daniel James.
-// Copyright 2021 Peter Dimov.
+// Copyright 2021, 2022 Peter Dimov.
 // Distributed under the Boost Software License, Version 1.0.
 // https://www.boost.org/LICENSE_1_0.txt
 
@@ -17,6 +17,7 @@ namespace container_hash
 template<class T> struct is_range;
 template<class T> struct is_contiguous_range;
 template<class T> struct is_unordered_range;
+template<class T> struct is_described_class;
 
 } // namespace container_hash
 

include/boost/container_hash/is_contiguous_range.hpp

@@ -10,7 +10,7 @@
 #include <boost/config.hpp>
 #include <boost/config/workaround.hpp>
 
-#if !defined(BOOST_NO_CXX11_DECLTYPE) && !defined(BOOST_NO_SFINAE_EXPR) && !BOOST_WORKAROUND(BOOST_GCC, < 40700)
+#if !defined(BOOST_NO_CXX11_DECLTYPE) && !defined(BOOST_NO_SFINAE_EXPR) && !BOOST_WORKAROUND(BOOST_GCC, < 40700) && !BOOST_WORKAROUND(BOOST_MSVC, < 1910)
 
 #include <boost/type_traits/is_integral.hpp>
 #include <boost/type_traits/declval.hpp>

include/boost/container_hash/is_described_class.hpp

@@ -0,0 +1,38 @@
+// Copyright 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#ifndef BOOST_HASH_IS_DESCRIBED_CLASS_HPP_INCLUDED
+#define BOOST_HASH_IS_DESCRIBED_CLASS_HPP_INCLUDED
+
+#include <boost/type_traits/integral_constant.hpp>
+#include <boost/type_traits/is_union.hpp>
+#include <boost/describe/bases.hpp>
+#include <boost/describe/members.hpp>
+
+namespace boost
+{
+namespace container_hash
+{
+
+#if defined(BOOST_DESCRIBE_CXX11)
+
+template<class T> struct is_described_class: boost::integral_constant<bool,
+    describe::has_describe_bases<T>::value &&
+    describe::has_describe_members<T>::value &&
+    !boost::is_union<T>::value>
+{
+};
+
+#else
+
+template<class T> struct is_described_class: boost::false_type
+{
+};
+
+#endif
+
+} // namespace container_hash
+} // namespace boost
+
+#endif // #ifndef BOOST_HASH_IS_DESCRIBED_CLASS_HPP_INCLUDED

test/CMakeLists.txt

@@ -1,4 +1,4 @@
-# Copyright 2018, 2019, 2021 Peter Dimov
+# Copyright 2018, 2019, 2021, 2022 Peter Dimov
 # Distributed under the Boost Software License, Version 1.0.
 # See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt
 
@@ -6,6 +6,7 @@ include(BoostTestJamfile OPTIONAL RESULT_VARIABLE HAVE_BOOST_TEST)
 
 if(HAVE_BOOST_TEST)
 
-boost_test_jamfile(FILE Jamfile.v2 LINK_LIBRARIES Boost::container_hash Boost::core Boost::utility)
+boost_test_jamfile(FILE Jamfile.v2
+  LINK_LIBRARIES Boost::container_hash Boost::core Boost::utility Boost::unordered)
 
 endif()

test/Jamfile.v2

@@ -101,3 +101,17 @@ run hash_unordered_map_test.cpp ;
 run is_range_test3.cpp ;
 run is_contiguous_range_test2.cpp ;
 run is_unordered_range_test2.cpp ;
+run is_contiguous_range_test3.cpp ;
+
+run is_described_class_test.cpp
+  : : : <warnings>extra ;
+run is_described_class_test2.cpp
+  : : : <warnings>extra ;
+run is_described_class_test3.cpp
+  : : : <warnings>extra ;
+
+run described_class_test.cpp
+  : : : <warnings>extra ;
+
+run hash_is_avalanching_test.cpp ;
+run hash_is_avalanching_test2.cpp ;

test/cmake_subdir_test/CMakeLists.txt

@@ -11,6 +11,8 @@ add_subdirectory(../.. boostorg/container_hash)
 add_subdirectory(../../../config boostorg/config)
 add_subdirectory(../../../type_traits boostorg/type_traits)
 add_subdirectory(../../../static_assert boostorg/static_assert)
+add_subdirectory(../../../describe boostorg/describe)
+add_subdirectory(../../../mp11 boostorg/mp11)
 
 add_executable(quick ../quick.cpp)
 target_link_libraries(quick Boost::container_hash)

test/described_class_test.cpp

@@ -0,0 +1,159 @@
+// Copyright 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#if defined(__clang__)
+# pragma clang diagnostic ignored "-Wunused-private-field"
+#endif
+
+#include <boost/container_hash/hash.hpp>
+#include <boost/describe/class.hpp>
+#include <boost/describe/operators.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+
+#if !defined(BOOST_DESCRIBE_CXX14)
+
+#include <boost/config/pragma_message.hpp>
+
+BOOST_PRAGMA_MESSAGE( "Skipping test because BOOST_DESCRIBE_CXX14 is not defined" )
+
+int main() {}
+
+#else
+
+struct X1
+{
+    int m;
+    explicit X1( int m_ ): m( m_ ) {}
+};
+
+BOOST_DESCRIBE_STRUCT( X1, (), (m) )
+
+struct X2
+{
+    int m;
+    explicit X2( int m_ ): m( m_ ) {}
+};
+
+BOOST_DESCRIBE_STRUCT( X2, (), (m) )
+
+struct X3
+{
+    int m;
+    explicit X3( int m_ ): m( m_ ) {}
+};
+
+BOOST_DESCRIBE_STRUCT( X3, (), (m) )
+
+class Y: public X1, protected X2, private X3
+{
+public:
+
+    int m1;
+
+protected:
+
+    int m2;
+
+private:
+
+    int m3;
+
+public:
+
+    Y( int x1, int x2, int x3, int m1_, int m2_, int m3_ ):
+      X1( x1 ), X2( x2 ), X3( x3 ), m1( m1_ ), m2( m2_ ), m3( m3_ ) {}
+
+    BOOST_DESCRIBE_CLASS( Y, (X1, X2, X3), (m1), (m2), (m3) )
+};
+
+using boost::describe::operators::operator==;
+using boost::describe::operators::operator!=;
+using boost::describe::operators::operator<<;
+
+int main()
+{
+    Y y1( 0, 0, 0, 0, 0, 0 );
+
+    BOOST_TEST_EQ( y1, y1 );
+    BOOST_TEST_EQ( boost::hash<Y>()(y1), boost::hash<Y>()(y1) );
+
+    Y y2( 1, 0, 0, 0, 0, 0 );
+
+    BOOST_TEST_NE( y1, y2 );
+    BOOST_TEST_NE( boost::hash<Y>()(y1), boost::hash<Y>()(y2) );
+
+    Y y3( 0, 1, 0, 0, 0, 0 );
+
+    BOOST_TEST_NE( y1, y3 );
+    BOOST_TEST_NE( boost::hash<Y>()(y1), boost::hash<Y>()(y3) );
+
+    BOOST_TEST_NE( y2, y3 );
+    BOOST_TEST_NE( boost::hash<Y>()(y2), boost::hash<Y>()(y3) );
+
+    Y y4( 0, 0, 1, 0, 0, 0 );
+
+    BOOST_TEST_NE( y1, y4 );
+    BOOST_TEST_NE( boost::hash<Y>()(y1), boost::hash<Y>()(y4) );
+
+    BOOST_TEST_NE( y2, y4 );
+    BOOST_TEST_NE( boost::hash<Y>()(y2), boost::hash<Y>()(y4) );
+
+    BOOST_TEST_NE( y3, y4 );
+    BOOST_TEST_NE( boost::hash<Y>()(y3), boost::hash<Y>()(y4) );
+
+    Y y5( 0, 0, 0, 1, 0, 0 );
+
+    BOOST_TEST_NE( y1, y5 );
+    BOOST_TEST_NE( boost::hash<Y>()(y1), boost::hash<Y>()(y5) );
+
+    BOOST_TEST_NE( y2, y5 );
+    BOOST_TEST_NE( boost::hash<Y>()(y2), boost::hash<Y>()(y5) );
+
+    BOOST_TEST_NE( y3, y5 );
+    BOOST_TEST_NE( boost::hash<Y>()(y3), boost::hash<Y>()(y5) );
+
+    BOOST_TEST_NE( y4, y5 );
+    BOOST_TEST_NE( boost::hash<Y>()(y4), boost::hash<Y>()(y5) );
+
+    Y y6( 0, 0, 0, 0, 1, 0 );
+
+    BOOST_TEST_NE( y1, y6 );
+    BOOST_TEST_NE( boost::hash<Y>()(y1), boost::hash<Y>()(y6) );
+
+    BOOST_TEST_NE( y2, y6 );
+    BOOST_TEST_NE( boost::hash<Y>()(y2), boost::hash<Y>()(y6) );
+
+    BOOST_TEST_NE( y3, y6 );
+    BOOST_TEST_NE( boost::hash<Y>()(y3), boost::hash<Y>()(y6) );
+
+    BOOST_TEST_NE( y4, y6 );
+    BOOST_TEST_NE( boost::hash<Y>()(y4), boost::hash<Y>()(y6) );
+
+    BOOST_TEST_NE( y5, y6 );
+    BOOST_TEST_NE( boost::hash<Y>()(y5), boost::hash<Y>()(y6) );
+
+    Y y7( 0, 0, 0, 0, 0, 1 );
+
+    BOOST_TEST_NE( y1, y7 );
+    BOOST_TEST_NE( boost::hash<Y>()(y1), boost::hash<Y>()(y7) );
+
+    BOOST_TEST_NE( y2, y7 );
+    BOOST_TEST_NE( boost::hash<Y>()(y2), boost::hash<Y>()(y7) );
+
+    BOOST_TEST_NE( y3, y7 );
+    BOOST_TEST_NE( boost::hash<Y>()(y3), boost::hash<Y>()(y7) );
+
+    BOOST_TEST_NE( y4, y7 );
+    BOOST_TEST_NE( boost::hash<Y>()(y4), boost::hash<Y>()(y7) );
+
+    BOOST_TEST_NE( y5, y7 );
+    BOOST_TEST_NE( boost::hash<Y>()(y5), boost::hash<Y>()(y7) );
+
+    BOOST_TEST_NE( y6, y7 );
+    BOOST_TEST_NE( boost::hash<Y>()(y6), boost::hash<Y>()(y7) );
+
+    return boost::report_errors();
+}
+
+#endif

test/hash_container_test.cpp

@@ -48,5 +48,13 @@ int main()
     test<float>();
     test<double>();
 
+#if defined(__cpp_char8_t) && __cpp_char8_t >= 201811L
+    test<char8_t>();
+#endif
+
+#if defined(__cpp_lib_byte) && __cpp_lib_byte >= 201603L
+    test<std::byte>();
+#endif
+
     return boost::report_errors();
 }

test/hash_function_pointer_test.cpp

@@ -14,8 +14,8 @@
 #include <boost/core/lightweight_test.hpp>
 #include "./compile_time.hpp"
 
-void void_func1() { static int x = 1; ++x; }
-void void_func2() { static int x = 2; --x; }
+void void_func1() { static int x = 1; ++x; (void)x; }
+void void_func2() { static int x = 2; --x; (void)x; }
 int int_func1(int) { return 0; }
 int int_func2(int) { return 1; }
 

test/hash_is_avalanching_test.cpp

@@ -0,0 +1,57 @@
+// Copyright 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/container_hash/hash.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <boost/config.hpp>
+#include <boost/config/pragma_message.hpp>
+
+#if defined(BOOST_NO_CXX11_HDR_TYPE_TRAITS)
+
+BOOST_PRAGMA_MESSAGE( "Test skipped, BOOST_NO_CXX11_HDR_TYPE_TRAITS is defined" )
+int main() {}
+
+#elif defined(BOOST_NO_CXX11_TEMPLATE_ALIASES)
+
+BOOST_PRAGMA_MESSAGE( "Test skipped, BOOST_NO_CXX11_TEMPLATE_ALIASES is defined" )
+int main() {}
+
+#else
+
+#include <boost/unordered/hash_traits.hpp>
+#include <string>
+
+enum my_char { min = 0, max = 255 };
+
+int main()
+{
+    using boost::unordered::hash_is_avalanching;
+
+    BOOST_TEST_TRAIT_TRUE(( hash_is_avalanching< boost::hash<std::string> > ));
+    BOOST_TEST_TRAIT_TRUE(( hash_is_avalanching< boost::hash<std::wstring> > ));
+
+#if !defined(BOOST_NO_CXX11_CHAR16_T)
+
+    BOOST_TEST_TRAIT_TRUE(( hash_is_avalanching< boost::hash<std::u16string> > ));
+
+#endif
+
+#if !defined(BOOST_NO_CXX11_CHAR32_T)
+
+    BOOST_TEST_TRAIT_TRUE(( hash_is_avalanching< boost::hash<std::u32string> > ));
+
+#endif
+
+#if defined(__cpp_char8_t) && __cpp_char8_t >= 201811L
+
+    BOOST_TEST_TRAIT_TRUE(( hash_is_avalanching< boost::hash< std::basic_string<char8_t> > > ));
+
+#endif
+
+    BOOST_TEST_TRAIT_FALSE(( hash_is_avalanching< boost::hash<std::basic_string<my_char> > > ));
+
+    return boost::report_errors();
+}
+
+#endif

test/hash_is_avalanching_test2.cpp

@@ -0,0 +1,62 @@
+// Copyright 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/container_hash/hash.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <boost/config.hpp>
+#include <boost/config/pragma_message.hpp>
+
+#if defined(BOOST_NO_CXX11_HDR_TYPE_TRAITS)
+
+BOOST_PRAGMA_MESSAGE( "Test skipped, BOOST_NO_CXX11_HDR_TYPE_TRAITS is defined" )
+int main() {}
+
+#elif defined(BOOST_NO_CXX11_TEMPLATE_ALIASES)
+
+BOOST_PRAGMA_MESSAGE( "Test skipped, BOOST_NO_CXX11_TEMPLATE_ALIASES is defined" )
+int main() {}
+
+#elif defined(BOOST_NO_CXX17_HDR_STRING_VIEW)
+
+BOOST_PRAGMA_MESSAGE( "Test skipped, BOOST_NO_CXX17_HDR_STRING_VIEW is defined" )
+int main() {}
+
+#else
+
+#include <boost/unordered/hash_traits.hpp>
+#include <string_view>
+
+enum my_char { min = 0, max = 255 };
+
+int main()
+{
+    using boost::unordered::hash_is_avalanching;
+
+    BOOST_TEST_TRAIT_TRUE(( hash_is_avalanching< boost::hash<std::string_view> > ));
+    BOOST_TEST_TRAIT_TRUE(( hash_is_avalanching< boost::hash<std::wstring_view> > ));
+
+#if !defined(BOOST_NO_CXX11_CHAR16_T)
+
+    BOOST_TEST_TRAIT_TRUE(( hash_is_avalanching< boost::hash<std::u16string_view> > ));
+
+#endif
+
+#if !defined(BOOST_NO_CXX11_CHAR32_T)
+
+    BOOST_TEST_TRAIT_TRUE(( hash_is_avalanching< boost::hash<std::u32string_view> > ));
+
+#endif
+
+#if defined(__cpp_char8_t) && __cpp_char8_t >= 201811L
+
+    BOOST_TEST_TRAIT_TRUE(( hash_is_avalanching< boost::hash< std::basic_string_view<char8_t> > > ));
+
+#endif
+
+    BOOST_TEST_TRAIT_FALSE(( hash_is_avalanching< boost::hash<std::basic_string_view<my_char> > > ));
+
+    return boost::report_errors();
+}
+
+#endif

test/is_contiguous_range_test.cpp

@@ -51,7 +51,7 @@ int main()
     BOOST_TEST_TRAIT_TRUE((is_contiguous_range<std::wstring const>));
 
 // std::vector doesn't have data() in C++03
-#if !defined(BOOST_NO_CXX11_DECLTYPE) && !defined(BOOST_NO_SFINAE_EXPR) && !BOOST_WORKAROUND(BOOST_GCC, < 40700)
+#if !defined(BOOST_NO_CXX11_DECLTYPE) && !defined(BOOST_NO_SFINAE_EXPR) && !BOOST_WORKAROUND(BOOST_GCC, < 40700) && !BOOST_WORKAROUND(BOOST_MSVC, < 1910)
     BOOST_TEST_TRAIT_TRUE((is_contiguous_range< std::vector<X> >));
     BOOST_TEST_TRAIT_TRUE((is_contiguous_range< std::vector<X> const >));
 #endif

test/is_contiguous_range_test2.cpp

@@ -50,7 +50,7 @@ int main()
 {
     using boost::container_hash::is_contiguous_range;
 
-#if !defined(BOOST_NO_CXX11_DECLTYPE) && !defined(BOOST_NO_SFINAE_EXPR) && !BOOST_WORKAROUND(BOOST_GCC, < 40700)
+#if !defined(BOOST_NO_CXX11_DECLTYPE) && !defined(BOOST_NO_SFINAE_EXPR) && !BOOST_WORKAROUND(BOOST_GCC, < 40700) && !BOOST_WORKAROUND(BOOST_MSVC, < 1910)
 
     BOOST_TEST_TRAIT_TRUE((is_contiguous_range<X1>));
 

test/is_contiguous_range_test3.cpp

@@ -0,0 +1,25 @@
+// Copyright 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/container_hash/is_contiguous_range.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <cstddef>
+
+struct X1
+{
+    char const* begin() const;
+    char const* end() const;
+    std::size_t size() const;
+
+    char data[16];
+};
+
+int main()
+{
+    using boost::container_hash::is_contiguous_range;
+
+    BOOST_TEST_TRAIT_FALSE((is_contiguous_range<X1>));
+
+    return boost::report_errors();
+}

test/is_described_class_test.cpp

@@ -0,0 +1,56 @@
+// Copyright 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/container_hash/is_described_class.hpp>
+#include <boost/describe/class.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <string>
+
+struct X1
+{
+};
+
+struct X2
+{
+    int m;
+};
+
+struct Y1
+{
+};
+
+BOOST_DESCRIBE_STRUCT( Y1, (), () )
+
+struct Y2: Y1
+{
+    int m;
+};
+
+BOOST_DESCRIBE_STRUCT( Y2, (Y1), (m) )
+
+int main()
+{
+    using boost::container_hash::is_described_class;
+
+    BOOST_TEST_TRAIT_FALSE((is_described_class<void>));
+    BOOST_TEST_TRAIT_FALSE((is_described_class<int>));
+    BOOST_TEST_TRAIT_FALSE((is_described_class<X1>));
+    BOOST_TEST_TRAIT_FALSE((is_described_class<X2>));
+    BOOST_TEST_TRAIT_FALSE((is_described_class<int[2]>));
+    BOOST_TEST_TRAIT_FALSE((is_described_class<std::string>));
+
+#if defined(BOOST_DESCRIBE_CXX14)
+
+    BOOST_TEST_TRAIT_TRUE((is_described_class<Y1>));
+    BOOST_TEST_TRAIT_TRUE((is_described_class<Y2>));
+
+#else
+
+    BOOST_TEST_TRAIT_FALSE((is_described_class<Y1>));
+    BOOST_TEST_TRAIT_FALSE((is_described_class<Y2>));
+
+#endif
+
+    return boost::report_errors();
+}

test/is_described_class_test2.cpp

@@ -0,0 +1,35 @@
+// Copyright 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/type_traits/integral_constant.hpp>
+#include <boost/describe/class.hpp>
+
+struct X
+{
+};
+
+BOOST_DESCRIBE_STRUCT( X, (), () )
+
+namespace boost
+{
+namespace container_hash
+{
+
+template<class T> struct is_described_class;
+template<> struct is_described_class<X>: boost::false_type {};
+
+} // namespace container_hash
+} // namespace boost
+
+#include <boost/container_hash/is_described_class.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+
+int main()
+{
+    using boost::container_hash::is_described_class;
+
+    BOOST_TEST_TRAIT_FALSE((is_described_class<X>));
+
+    return boost::report_errors();
+}

test/is_described_class_test3.cpp

@@ -0,0 +1,31 @@
+// Copyright 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/container_hash/is_described_class.hpp>
+#include <boost/describe/class.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+
+union Y1
+{
+};
+
+BOOST_DESCRIBE_STRUCT( Y1, (), () )
+
+union Y2
+{
+    int m1;
+    float m2;
+};
+
+BOOST_DESCRIBE_STRUCT( Y2, (), (m1, m2) )
+
+int main()
+{
+    using boost::container_hash::is_described_class;
+
+    BOOST_TEST_TRAIT_FALSE((is_described_class<Y1>));
+    BOOST_TEST_TRAIT_FALSE((is_described_class<Y2>));
+
+    return boost::report_errors();
+}