Merge branch 'develop'

.github/workflows/ci.yml

@@ -142,9 +142,8 @@ jobs:
           - toolset: clang
             compiler: clang++-16
             cxxstd: "03,11,14,17,20,2b"
-            os: ubuntu-latest
+            os: ubuntu-24.04
             install: clang-16
-            container: ubuntu:24.04
           - toolset: clang
             compiler: clang++-17
             cxxstd: "03,11,14,17,20,2b"
@@ -225,10 +224,6 @@ jobs:
             cxxstd: 14,latest
             addrmd: 32,64
             os: windows-2019
-          - toolset: msvc-14.1
-            cxxstd: "11,14,17,20,latest"
-            addrmd: 32,64
-            os: windows-2019
           - toolset: msvc-14.2
             cxxstd: "14,17,20,latest"
             addrmd: 32,64

doc/11_development.qbk

@@ -50,6 +50,18 @@ In the general case, the internal representation is something equivalent to:
     alignas(T) char _value [sizeof(T)];
   };
 
+or:
+
+  template <typename T>
+  class Optional
+  {
+    bool _has_value = false;
+    union {
+      T         _value;
+      DummyType _non_value;
+    };
+  };
+
 Next, because we need to pass around these "optional" `int`s as normal `int`s,
 like returning them from functions, when copying, we need to copy `_has_value`,
 which indicates whether we have the value or not, and, if we do have value, and

doc/27_ref_optional_synopsis.qbk

@@ -197,6 +197,9 @@ They are empty, trivially copyable classes with disabled default constructor.
         template<class F> constexpr auto flat_map( F f ) & -> ``['see below]``; ``[link reference_optional_flat_map __GO_TO__]``
         template<class F> constexpr auto flat_map( F f ) && -> ``['see below]``; ``[link reference_optional_flat_map_move __GO_TO__]``
 
+        constexpr operator optional<T&>() & noexcept; ``[link reference_optional_conversion_to_ref __GO_TO__]``
+        constexpr operator optional<T const&>() const& noexcept; ``[link reference_optional_conversion_to_ref __GO_TO__]``
+
         T const* get_ptr() const ; ``[link reference_optional_get_ptr __GO_TO__]``
         T*       get_ptr() ; ``[link reference_optional_get_ptr __GO_TO__]``
 

doc/28_ref_optional_semantics.qbk

@@ -2,6 +2,7 @@
     Boost.Optional
 
     Copyright (c) 2003-2007 Fernando Luis Cacciola Carballal
+    Copyright (C) 2014 - 2026 Andrzej Krzemieński.
 
     Distributed under the Boost Software License, Version 1.0.
     (See accompanying file LICENSE_1_0.txt or copy at
@@ -25,31 +26,31 @@ __SPACE__
 
 [: `constexpr optional<T>::optional() noexcept;`]
 
-* [*Effect:] Default-Constructs an `optional`.
-* [*Postconditions:] `*this` is [_uninitialized].
-* [*Notes:] T's default constructor [_is not] called.
+* [*Postconditions:] `*this` does ['not] contain a value (is "uninitialized").
+* [*Remarks:] No contained value is initialized. For every object type `T` these constructors are core constant expressions.
 * [*Example:]
 ``
-optional<T> def ;
-assert ( !def ) ;
+optional<T> oN ;
+assert ( !oN ) ;
 ``
 
 __SPACE__
 
-[#reference_optional_constructor_none_t]
 
+[#reference_optional_constructor_none_t]
 [: `constexpr optional<T>::optional( none_t ) noexcept;`]
 
-* [*Effect:] Constructs an `optional` uninitialized.
-* [*Postconditions:] `*this` is [_uninitialized].
-* [*Notes:] `T`'s default constructor [_is not] called. The expression
+* [*Postconditions:] `*this` does ['not] contain a value (is "uninitialized").
+* [*Remarks:] No contained value is initialized. For every object type `T` these constructors are core constant expressions. The expression
 `boost::none` denotes an instance of `boost::none_t` that can be used as
 the parameter.
 * [*Example:]
 ``
 #include <boost/none.hpp>
+
 optional<T> n(none) ;
 assert ( !n ) ;
+assert ( n == none ) ;
 ``
 
 __SPACE__
@@ -752,6 +753,26 @@ __SPACE__
 
 __SPACE__
 
+
+[#reference_optional_conversion_to_ref]
+
+[: `constexpr optional<T>::operator optional<T&>() & noexcept ;`]
+
+* [*Returns:] If `*this` contains a value `optional<T&>(**this)`, otherwise `optional<T&>()`.
+
+[: `constexpr optional<T>::operator optional<T const&>() const& noexcept ;`]
+
+* [*Returns:] If `*this` contains a value `optional<T const&>(**this)`, otherwise `optional<T&>()`.
+
+* [*Example:]
+``
+const optional<int> oi = 1;
+optional<const int&> ri = oi;
+``
+
+__SPACE__
+
+
 [#reference_optional_get_value_or_value]
 
 [: `T const& optional<T>::get_value_or( T const& default) const ;`]

doc/90_dependencies.qbk

@@ -72,7 +72,6 @@ The implementation uses the following other Boost modules:
 # assert
 # config
 # core
-# static_assert
 # throw_exception
 # type_traits
 

doc/91_comparison_with_std.qbk

@@ -47,7 +47,17 @@
   `std::ranges::find(rng, boost::none)`] [`std::vector<optional<int>> rng;`
 
   `std::ranges::find(rng, boost::optional<int>{})`] [optional<T> is never [@https://en.cppreference.com/w/cpp/concepts/equality_comparable `std::equality_comparable_with`] `nullopt_t` in `std`. ] ]
+
+  [ [```
+  void test(vector<optional<T>> rng, T val) {
+    std::ranges::find(rng, val);
+  }
+  ```] [```
+  void test(vector<optional<T>> rng, T val) {
+    std::ranges::find(rng, make_optional(val));
+  }
+  ```] [For `std::optional`, code without `make_optional()` compiles but is ['undefined behavior] when `T` is itself an `optional`. ] ]
+
 ]
 
-
 [endsect][/ std_comp]

doc/92_relnotes.qbk

@@ -18,7 +18,7 @@
   `constexpr` support:
 
     * In C++11, some constructors and `const`-qualified accessors become usable
-      in compile-time contexts (are ['core constant expressions] for types
+      in compile-time contexts (are ['core constant expressions]) for types
       satisfying certain constraints.
     * In C++14 even some mutating operations become core constant expressions (those
       that do not require changing the state of `optional` from not having a value to
@@ -26,7 +26,7 @@
     * In C++17 all constructors (including copy and move) become core constant expressions
       for co-operating types.
 
-  This addresses [@https://github.com/boostorg/optional/issues/143 issue #143].
+  This addresses issues [@https://github.com/boostorg/optional/issues/132 #132] and [@https://github.com/boostorg/optional/issues/143 #143].
 
 * *Breaking change.* In the said implementation, abandoned the mechanism for customizing
   `swap`. Hardly anyone knows about this mechanism and it was never documented.
@@ -37,10 +37,31 @@
   * Construct `o = u`, where `o` is of type `optional<T>` and `u` is of type `U` convertible to `T`,
     does not create a temporary `T`.
 
+* In the said implementation, added a conversion from `optional<T>&` to `optional<T&>`. This addresses [@https://github.com/boostorg/optional/issues/142 issue #142].
+
 * `none_t` is now `std::equality_comparable`, which means that `none_t` and `optional<T>`
   model concept `std::equality_comparable_with` (for `std::equality_comparable` `T`s),
   which means that you can `std::ranges::find(rng, boost::none)` for a range of optional objects.
 
+* *Warning.* In the future releases we intend to introduce the range interface
+  in `optional`, so that `std::ranges::range<optional<T>>` will be `true`.
+  This may affect the overload resolution in programs that make decisions based
+  on predicates such as `std::ranges::range`. For instance, the following code
+  will start behaving differently:
+
+  ```
+  template <typename T>
+  void serialize(T const& v)
+  {
+    if constexpr (std::ranges::range<T>)
+      serialize_as_range(v);
+    else if constexpr (custom::is_optional_like<T>)
+      serialize_as_optional(v);
+    else
+      serialize_as_value(v);
+  }
+  ```
+
 [heading Boost Release 1.87]
 
 * *Breaking change.* Dropped support for C++03. C++11 is now the required minimum; at least some C++11 features.

include/boost/optional/detail/union_optional.hpp

@@ -122,6 +122,15 @@ struct constexpr_guarded_storage
     BOOST_CXX14_CONSTEXPR void reset () noexcept { init_ = false; }
 
     //~constexpr_guarded_storage() = default;
+
+#if (defined(_MSC_VER) && 1910 <= _MSC_VER && _MSC_VER <= 1916)
+  // Workaround for MSVC 14.1x bug where it eagerly tries to define the copy/move operations
+  // these are declared but never defined
+    constexpr_guarded_storage(const constexpr_guarded_storage&);
+    constexpr_guarded_storage(constexpr_guarded_storage&&);
+    constexpr_guarded_storage& operator=(const constexpr_guarded_storage&);
+    constexpr_guarded_storage& operator=(constexpr_guarded_storage&&);
+#endif
 };
 
 
@@ -155,6 +164,15 @@ struct fallback_guarded_storage
     }
 
     ~fallback_guarded_storage() { if (init_) storage_.value_.T::~T(); }
+
+#if (defined(_MSC_VER) && 1910 <= _MSC_VER && _MSC_VER <= 1916)
+// Workaround for MSVC 14.1x bug where it eagerly tries to define the copy/move operations
+// These are declared but never defined
+  fallback_guarded_storage(const fallback_guarded_storage&);
+  fallback_guarded_storage(fallback_guarded_storage&&);
+  fallback_guarded_storage& operator=(const fallback_guarded_storage&);
+  fallback_guarded_storage& operator=(fallback_guarded_storage&&);
+#endif
 };
 
 
@@ -349,7 +367,9 @@ namespace boost {
     }
 
     template <typename U,
-              BOOST_OPTIONAL_REQUIRES(::std::is_constructible<T, U&&>)>
+              BOOST_OPTIONAL_REQUIRES(::std::is_constructible<T, U&&>),
+              BOOST_OPTIONAL_REQUIRES(!optional_detail::is_typed_in_place_factory<U>),
+              BOOST_OPTIONAL_REQUIRES(!optional_detail::is_in_place_factory<U>)>
     constexpr explicit optional(U&& v)
     : storage(optional_ns::in_place_init, optional_detail::forward_<U>(v))
     {}
@@ -359,6 +379,20 @@ namespace boost {
     : storage(in_place_init, optional_detail::forward_<Args>(args)...)
     {}
 
+    BOOST_CXX14_CONSTEXPR operator optional<T&>() & noexcept
+    {
+      return this->has_value() ? optional<T&>(**this) : optional<T&>();
+    }
+
+    BOOST_CONSTEXPR operator optional<const T&>() const& noexcept
+    {
+      return this->has_value() ? optional<const T&>(**this) : optional<const T&>();
+    }
+
+    BOOST_CXX14_CONSTEXPR operator optional<T&>() && noexcept = delete;
+    BOOST_CONSTEXPR operator optional<const T&>() const&& noexcept = delete;
+
+
     BOOST_CXX14_CONSTEXPR void reset() noexcept
     {
       storage.reset();
@@ -463,7 +497,9 @@ namespace boost {
               BOOST_OPTIONAL_REQUIRES(!::std::is_same<typename ::std::decay<U>::type, optional>),
               BOOST_OPTIONAL_REQUIRES(!optional_detail::conjunction<::std::is_scalar<T>, ::std::is_same<T, BOOST_OPTIONAL_DECAY(U)>>),
               BOOST_OPTIONAL_REQUIRES(::std::is_constructible<T, U>),
-              BOOST_OPTIONAL_REQUIRES(::std::is_assignable<T&, U>)
+              BOOST_OPTIONAL_REQUIRES(::std::is_assignable<T&, U>),
+              BOOST_OPTIONAL_REQUIRES(!optional_detail::is_typed_in_place_factory<U>),
+              BOOST_OPTIONAL_REQUIRES(!optional_detail::is_in_place_factory<U>)
              >
     BOOST_OPTIONAL_CXX20_CONSTEXPR optional& operator=(U&& v)
     {

test/Jamfile.v2

@@ -28,7 +28,6 @@ project
             cxx11_explicit_conversion_operators
 #            cxx11_noexcept
             cxx11_rvalue_references
-            cxx11_static_assert
             cxx11_variadic_templates
         ]
     ;
@@ -81,6 +80,7 @@ compile-fail optional_test_fail3b.cpp ;
 compile-fail optional_test_ref_fail1.cpp ;
 compile-fail optional_test_ref_fail3.cpp ;
 compile-fail optional_test_ref_fail4.cpp ;
+compile-fail optional_test_ref_fail_convert_from_temporary_optional_T.cpp ;
 compile-fail optional_test_inplace_fail.cpp ;
 compile-fail optional_test_inplace_fail2.cpp ;
 compile-fail optional_test_fail_implicit_bool_convert.cpp ;

test/optional_test_constexpr.cpp

@@ -10,7 +10,6 @@
 //  akrzemi1@gmail.com
 
 #include "boost/optional.hpp"
-#include <string>
 
 #ifdef BOOST_OPTIONAL_USES_UNION_IMPLEMENTATION
 
@@ -130,24 +129,4 @@ namespace test_optional_ref
   static_assert(*iref == 9, "");
 }
 
-namespace test_msvc_14_1
-{
-  struct Aggr
-  {
-    boost::optional<std::string> os;
-  };
-
-  void test()
-  {
-    Aggr a;
-    Aggr b = a;
-    b = a;
-    Aggr c = Aggr();
-    b = Aggr();
-    (void)a;
-    (void)b;
-    (void)c;
-  }
-}
-
 #endif // BOOST_OPTIONAL_USES_UNION_IMPLEMENTATION

test/optional_test_inplace_factory.cpp

@@ -105,9 +105,42 @@ void test_assign()
 #endif
 }
 
+// begin Boost.Log case
+
+template <typename CharT>
+struct basic_formatter
+{
+  template< typename FunT >
+  basic_formatter(FunT&& fun) {}
+
+  template< typename FunT >
+  basic_formatter& operator= (FunT&& fun)
+  {
+      return *this;
+  }
+};
+
+template< typename CharT>
+struct chained_formatter
+{
+};
+
+void test_boost_log_case()
+{
+#ifndef BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT
+
+  boost::optional<basic_formatter<char>> of( boost::in_place(chained_formatter<char>()) );
+  of = boost::in_place(chained_formatter<char>());
+
+#endif //BOOST_OPTIONAL_NO_INPLACE_FACTORY_SUPPORT
+}
+
+// end Boost.Log case
+
 int main()
 {
   test_ctor();
   test_assign();
+  test_boost_log_case();
   return boost::report_errors();
 }

test/optional_test_msvc_bug_workaround.cpp

@@ -32,6 +32,7 @@ void test()
   //BOOST_TEST(v);
   boost::optional<boost::optional<int>> vv;
   bool xx = vv?true : false;
+  (void)xx;
   BOOST_TEST_EQ(*v, 7);
 #endif
 }

test/optional_test_ref_fail_convert_from_temporary_optional_T.cpp

@@ -0,0 +1,21 @@
+// Copyright (C) 2003, Fernando Luis Cacciola Carballal.
+//
+// Use, modification, and distribution is subject to 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)
+//
+// See http://www.boost.org/lib/optional for documentation.
+//
+// You are welcome to contact the author at:
+//  fernando_cacciola@hotmail.com
+//
+#include "boost/optional.hpp"
+
+//
+// THIS TEST SHOULD FAIL TO COMPILE
+//
+void optional_reference__test_no_converting_initialization()
+{
+  boost::optional<const int&> o (boost::optional<int>(1));
+  (void)o;
+}

test/optional_test_ref_to_val.cpp

@@ -24,7 +24,13 @@ using boost::none;
 struct Value
 {
   int val;
-  explicit Value(int v) : val(v) {}
+  BOOST_CONSTEXPR explicit Value(int v) : val(v) {}
+};
+
+struct Guard
+{
+  int val;
+  BOOST_CONSTEXPR explicit Guard(int v) : val(v) {}
 };
 
 int val(int const& i)
@@ -37,6 +43,11 @@ int val(Value const& v)
   return v.val;
 }
 
+int val(Guard const& v)
+{
+  return v.val;
+}
+
 template <typename Tref>
 optional<Tref&> make_opt_ref(Tref& v)
 {
@@ -47,21 +58,21 @@ template <typename Tval, typename Tref>
 void test_construct_from_optional_ref()
 {
     Tref v1 (1), v2 (2);
-    
+
     optional<Tref&> opt_ref0;
     optional<Tref&> opt_ref1 (v1);
-    
+
     optional<Tval> opt_val0 (opt_ref0);
     optional<Tval> opt_val1 (opt_ref1);
     optional<Tval> opt_val2 (make_opt_ref(v2));
-    
+
     BOOST_TEST (!opt_val0);
     BOOST_TEST (opt_val1);
     BOOST_TEST (opt_val2);
-    
+
     BOOST_TEST_EQ (1, val(*opt_val1));
     BOOST_TEST_EQ (2, val(*opt_val2));
-    
+
     BOOST_TEST (boost::addressof(*opt_val1) != boost::addressof(v1));
     BOOST_TEST (boost::addressof(*opt_val2) != boost::addressof(v2));
 }
@@ -70,29 +81,121 @@ template <typename Tval, typename Tref>
 void test_assign_from_optional_ref()
 {
     Tref v1 (1), v2 (2);
-    
+
     optional<Tref&> opt_ref0;
     optional<Tref&> opt_ref1 (v1);
-    
+
     optional<Tval> opt_val0;
     optional<Tval> opt_val1;
     optional<Tval> opt_val2;
-    
+
     opt_val0 = opt_ref0;
     opt_val1 = opt_ref1;
     opt_val2 = make_opt_ref(v2);
-    
+
     BOOST_TEST (!opt_val0);
     BOOST_TEST (opt_val1);
     BOOST_TEST (opt_val2);
-    
+
     BOOST_TEST_EQ (1, val(*opt_val1));
     BOOST_TEST_EQ (2, val(*opt_val2));
-    
+
     BOOST_TEST (boost::addressof(*opt_val1) != boost::addressof(v1));
     BOOST_TEST (boost::addressof(*opt_val2) != boost::addressof(v2));
 }
 
+template <typename T>
+void test_convert_optional_T_to_optional_T_ref()
+{
+#ifdef BOOST_OPTIONAL_USES_UNION_IMPLEMENTATION
+  using boost::optional;
+  using boost::in_place_init;
+
+  { // optional<T>& -> optional<T&>
+    optional<T> ovN, ov1(in_place_init, 1), ov2(in_place_init, 2);
+
+    optional<T&> orN = ovN;
+    optional<T&> or1 = ov1;
+    optional<T&> or2 = ov2;
+
+    BOOST_TEST_EQ (!!orN, !!ovN);
+    BOOST_TEST_EQ (!!or1, !!ov1);
+    BOOST_TEST_EQ (!!or2, !!ov2);
+
+    BOOST_TEST (or1);
+    BOOST_TEST (or2);
+    BOOST_TEST_EQ (val(*or1), 1);
+    BOOST_TEST_EQ (val(*or2), 2);
+    BOOST_TEST (boost::addressof(*or1) == boost::addressof(*ov1));
+    BOOST_TEST (boost::addressof(*or2) == boost::addressof(*ov2));
+  }
+
+  { // const optional<T>& -> optional<const T&>
+    constexpr optional<T> ovN;
+    constexpr optional<T> ov1(in_place_init, 1);
+    constexpr optional<T> ov2(in_place_init, 2);
+
+    optional<const T&> orN = ovN;
+    optional<const T&> or1 = ov1;
+    optional<const T&> or2 = ov2;
+
+    BOOST_TEST_EQ (!!orN, !!ovN);
+    BOOST_TEST_EQ (!!or1, !!ov1);
+    BOOST_TEST_EQ (!!or2, !!ov2);
+
+    BOOST_TEST (or1);
+    BOOST_TEST (or2);
+    BOOST_TEST_EQ (val(*or1), 1);
+    BOOST_TEST_EQ (val(*or2), 2);
+    BOOST_TEST (boost::addressof(*or1) == boost::addressof(*ov1));
+    BOOST_TEST (boost::addressof(*or2) == boost::addressof(*ov2));
+  }
+
+  { // optional<const T>& -> optional<const T&>
+    optional<const T> ovN;
+    optional<const T> ov1(in_place_init, 1);
+    optional<const T> ov2(in_place_init, 2);
+
+    optional<const T&> orN = ovN;
+    optional<const T&> or1 = ov1;
+    optional<const T&> or2 = ov2;
+
+    BOOST_TEST_EQ (!!orN, !!ovN);
+    BOOST_TEST_EQ (!!or1, !!ov1);
+    BOOST_TEST_EQ (!!or2, !!ov2);
+
+    BOOST_TEST (or1);
+    BOOST_TEST (or2);
+    BOOST_TEST_EQ (val(*or1), 1);
+    BOOST_TEST_EQ (val(*or2), 2);
+    BOOST_TEST (boost::addressof(*or1) == boost::addressof(*ov1));
+    BOOST_TEST (boost::addressof(*or2) == boost::addressof(*ov2));
+  }
+
+  { // optional<T>& -> optional<const T&>
+    optional<T> ovN;
+    optional<T> ov1(in_place_init, 1);
+    optional<T> ov2(in_place_init, 2);
+
+    optional<const T&> orN = ovN;
+    optional<const T&> or1 = ov1;
+    optional<const T&> or2 = ov2;
+
+    BOOST_TEST_EQ (!!orN, !!ovN);
+    BOOST_TEST_EQ (!!or1, !!ov1);
+    BOOST_TEST_EQ (!!or2, !!ov2);
+
+    BOOST_TEST (or1);
+    BOOST_TEST (or2);
+    BOOST_TEST_EQ (val(*or1), 1);
+    BOOST_TEST_EQ (val(*or2), 2);
+    BOOST_TEST (boost::addressof(*or1) == boost::addressof(*ov1));
+    BOOST_TEST (boost::addressof(*or2) == boost::addressof(*ov2));
+  }
+
+#endif // BOOST_OPTIONAL_USES_UNION_IMPLEMENTATION
+}
+
 
 int main()
 {
@@ -100,17 +203,21 @@ int main()
     test_construct_from_optional_ref<int, int const>();
     test_construct_from_optional_ref<int const, int const>();
     test_construct_from_optional_ref<int const, int>();
-    
+
     test_construct_from_optional_ref<Value, Value>();
     test_construct_from_optional_ref<Value, Value const>();
     test_construct_from_optional_ref<Value const, Value const>();
     test_construct_from_optional_ref<Value const, Value>();
-    
+
     test_assign_from_optional_ref<int, int>();
     test_assign_from_optional_ref<int, int const>();
 
     test_assign_from_optional_ref<Value, Value>();
     test_assign_from_optional_ref<Value, Value const>();
 
+    test_convert_optional_T_to_optional_T_ref<int>();
+    test_convert_optional_T_to_optional_T_ref<Value>();
+    test_convert_optional_T_to_optional_T_ref<Guard>();
+
     return boost::report_errors();
 }