fix bug in copy construction of optional<bool>

fix: add -Wmaybe-uninitialized pragma to union storage constructors

doc/92_relnotes.qbk

@@ -11,6 +11,10 @@
 
 [section:relnotes Release Notes]
 
+[heading Boost Release 1.xx]
+
+* Fixed regression in the copy-initialization of `optional<bool>`. This fixes [@https://github.com/boostorg/optional/issues/146 issue #146].
+
 [heading Boost Release 1.91]
 
 * For compilers with full C++11 support (including "unrestricted  unions" and ref-qualifiers)

include/boost/optional/detail/optional_select_implementation.hpp

@@ -23,7 +23,8 @@
     !defined(BOOST_NO_CXX11_TRAILING_RESULT_TYPES) && \
     !defined(BOOST_NO_CXX11_UNRESTRICTED_UNION) &&    \
     !defined(BOOST_NO_CXX11_NOEXCEPT) &&              \
-    !defined(BOOST_NO_CXX11_DEFAULTED_MOVES)
+    !defined(BOOST_NO_CXX11_DEFAULTED_MOVES) &&       \
+    !defined(BOOST_OPTIONAL_CONFIG_DISABLE_UNION_OPTIONAL)
 # define BOOST_OPTIONAL_USES_UNION_IMPLEMENTATION
 #endif
 

include/boost/optional/detail/union_optional.hpp

@@ -74,9 +74,20 @@ union constexpr_union_storage_t
 
     constexpr constexpr_union_storage_t( trivial_init_t ) noexcept : dummy_() {};
 
+#if defined(BOOST_GCC) && (__GNUC__ >= 7)
+// false positive, see https://github.com/boostorg/variant2/issues/55,
+//   https://github.com/boostorg/url/issues/979
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
+#endif
+
     template <class... Args>
     constexpr constexpr_union_storage_t( Args&&... args ) : value_(forward_<Args>(args)...) {}
 
+#if defined(BOOST_GCC) && (__GNUC__ >= 7)
+# pragma GCC diagnostic pop
+#endif
+
     //~constexpr_union_storage_t() = default; // No need to destroy a trivially-destructible type
 };
 
@@ -88,9 +99,20 @@ union fallback_union_storage_t
 
   constexpr fallback_union_storage_t( trivial_init_t ) noexcept : dummy_() {};
 
+#if defined(BOOST_GCC) && (__GNUC__ >= 7)
+// false positive, see https://github.com/boostorg/variant2/issues/55,
+//   https://github.com/boostorg/url/issues/979
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
+#endif
+
   template <class... Args>
   constexpr fallback_union_storage_t( Args&&... args ) : value_(forward_<Args>(args)...) {}
 
+#if defined(BOOST_GCC) && (__GNUC__ >= 7)
+# pragma GCC diagnostic pop
+#endif
+
   ~fallback_union_storage_t(){} // My owner will destroy the `T` if needed.
                                 // Cannot default in a union with nontrivial `T`.
 };
@@ -369,7 +391,9 @@ namespace boost {
     template <typename 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>)>
+              BOOST_OPTIONAL_REQUIRES(!optional_detail::is_in_place_factory<U>),
+              BOOST_OPTIONAL_REQUIRES(!BOOST_OPTIONAL_IS_TAGGED(optional_detail::optional_tag, U))
+              >
     constexpr explicit optional(U&& v)
     : storage(optional_ns::in_place_init, optional_detail::forward_<U>(v))
     {}

test/Jamfile.v2

@@ -40,6 +40,7 @@ compile optional_test_constexpr.cpp ;
 compile optional_test_wuninitialized.cpp ;
 compile optional_test_fwd_header.cpp ;
 run optional_test_conversions_from_U.cpp ;
+run optional_test_constructors.cpp ;
 run optional_test_convert_from_T.cpp ;
 run optional_test_convert_assign.cpp ;
 run optional_test_empty_braces.cpp ;

test/optional_test_constructors.cpp

@@ -0,0 +1,287 @@
+// Copyright (C) 2026 Andrzej Krzemienski.
+//
+// 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:
+//  akrzemi1@gmail.com
+
+#include "boost/optional/optional.hpp"
+#include "boost/core/lightweight_test.hpp"
+#include <string>
+
+
+using boost::optional;
+using boost::none;
+
+struct MyBool
+{
+  bool b;
+  MyBool (bool b) : b(b) {}
+  operator bool() const { return b; };
+};
+
+struct MyExplicitBool
+{
+  bool b;
+  MyExplicitBool (bool b) : b(b) {}
+  operator bool() const { return b; };
+};
+
+struct Any
+{
+  template <typename... T>
+  Any(T&&...) {}
+};
+
+struct JustCopyMoveCtor
+{
+  JustCopyMoveCtor(JustCopyMoveCtor&&) = default;
+  JustCopyMoveCtor(JustCopyMoveCtor const&) = default;
+  JustCopyMoveCtor& operator=(JustCopyMoveCtor&&) = delete;
+  JustCopyMoveCtor& operator=(JustCopyMoveCtor const&) = delete;
+  JustCopyMoveCtor() = delete;
+};
+
+struct JustDefault
+{
+  JustDefault() = default;
+  JustDefault(JustDefault&&) = delete;
+};
+
+template <typename T>
+optional<T> empty_optional()
+{
+    return optional<T>(); // this is to avoid "the most vexing parse"
+}
+
+
+template <typename T, typename U>
+void direct_test_ctor_optional_T_from_empty_optional_T()
+{
+  optional<U> om;
+  const optional<U> oc;
+  BOOST_TEST(!om);
+  BOOST_TEST(!oc);
+
+  {
+    optional<T> ox = om;
+    BOOST_TEST(!ox);
+
+    optional<T> oy = oc;
+    BOOST_TEST(!oy);
+
+    optional<T> oz = empty_optional<U>();
+    BOOST_TEST(!oz);
+  }
+
+  {
+    optional<T> ox = {om};
+    BOOST_TEST(!ox);
+
+    optional<T> oy = {oc};
+    BOOST_TEST(!oy);
+
+    optional<T> oz = {empty_optional<U>()};
+    BOOST_TEST(!oz);
+  }
+
+  {
+    optional<T> ox{om};
+    BOOST_TEST(!ox);
+
+    optional<T> oy{oc};
+    BOOST_TEST(!oy);
+
+    optional<T> oz{empty_optional<U>()};
+    BOOST_TEST(!oz);
+  }
+
+  {
+    optional<T> ox(om);
+    BOOST_TEST(!ox);
+
+    optional<T> oy(oc);
+    BOOST_TEST(!oy);
+
+    optional<T> oz(empty_optional<U>());
+    BOOST_TEST(!oz);
+  }
+}
+
+template <typename T, typename U>
+void test_ctor_optional_T_from_empty_optional_T()
+{
+  direct_test_ctor_optional_T_from_empty_optional_T<T, U>();
+  direct_test_ctor_optional_T_from_empty_optional_T<const T, const U>();
+  direct_test_ctor_optional_T_from_empty_optional_T<optional<T>, optional<U>>();
+  direct_test_ctor_optional_T_from_empty_optional_T<optional<const T>, optional<const U>>();
+  direct_test_ctor_optional_T_from_empty_optional_T<const optional<T>, const optional<U>>();
+}
+
+template <typename T, typename U>
+void direct_test_ctor_optional_T_from_optional_U(U val)
+{
+  optional<U> om;
+  const optional<U> oc;
+  BOOST_TEST(!om);
+  BOOST_TEST(!oc);
+
+  {
+    optional<T> ox{om};
+    BOOST_TEST(!ox);
+
+    optional<T> oy{oc};
+    BOOST_TEST(!oy);
+
+    optional<T> oz{empty_optional<U>()};
+    BOOST_TEST(!oz);
+  }
+
+  {
+    optional<T> ox(om);
+    BOOST_TEST(!ox);
+
+    optional<T> oy(oc);
+    BOOST_TEST(!oy);
+
+    optional<T> oz(empty_optional<U>());
+    BOOST_TEST(!oz);
+  }
+
+  {
+    optional<U> om {val};
+    const optional<U> oc {val};
+
+    {
+      optional<T> ox{om};
+      BOOST_TEST(ox);
+
+      optional<T> oy{oc};
+      BOOST_TEST(oy);
+
+      optional<T> oz{boost::make_optional(val)};
+      BOOST_TEST(oz);
+    }
+    {
+      optional<T> ox(om);
+      BOOST_TEST(ox);
+
+      optional<T> oy(oc);
+      BOOST_TEST(oy);
+
+      optional<T> oz(boost::make_optional(val));
+      BOOST_TEST(oz);
+    }
+  }
+}
+
+template <typename T, typename U>
+void test_ctor_optional_T_from_optional_U(U val)
+{
+  direct_test_ctor_optional_T_from_optional_U<T>(val);
+}
+
+template <typename T>
+void direct_test_ctor_optional_T_from_valued_optional_T(T val)
+{
+  optional<T> om(val);
+  const optional<T> oc(val);
+  BOOST_TEST(om);
+  BOOST_TEST(oc);
+
+  {
+    optional<T> ox = om;
+    BOOST_TEST(ox);
+
+    optional<T> oy = oc;
+    BOOST_TEST(oy);
+
+    optional<T> oz = optional<T>(val);
+    BOOST_TEST(oz);
+  }
+  {
+    optional<T> ox = {om};
+    BOOST_TEST(ox);
+
+    optional<T> oy = {oc};
+    BOOST_TEST(oy);
+
+    optional<T> oz = {optional<T>(val)};
+    BOOST_TEST(oz);
+  }
+}
+
+template <typename T>
+void test_ctor_optional_T_from_valued_optional_T(T val)
+{
+  direct_test_ctor_optional_T_from_valued_optional_T<T>(val);
+  direct_test_ctor_optional_T_from_valued_optional_T<optional<T>>(val);
+  direct_test_ctor_optional_T_from_valued_optional_T<const T>(val);
+  direct_test_ctor_optional_T_from_optional_U<T, T>(val);
+  direct_test_ctor_optional_T_from_optional_U<optional<T>, optional<T>>(val);
+}
+
+template <typename T>
+void direct_test_inplace_tag_constructor()
+{
+  {
+    optional<T> ox (boost::in_place_init);
+    BOOST_TEST(ox);
+  }
+  {
+    optional<T> ox {boost::in_place_init};
+    BOOST_TEST(ox);
+  }
+}
+
+template <typename T>
+void test_inplace_tag_constructor()
+{
+  direct_test_inplace_tag_constructor<T>();
+  direct_test_inplace_tag_constructor<optional<T>>();
+}
+
+
+int main()
+{
+    test_ctor_optional_T_from_empty_optional_T<int, int>();
+    test_ctor_optional_T_from_empty_optional_T<long, long>();
+    test_ctor_optional_T_from_empty_optional_T<std::string, std::string>();
+    test_ctor_optional_T_from_empty_optional_T<JustCopyMoveCtor, JustCopyMoveCtor>();
+    test_ctor_optional_T_from_empty_optional_T<MyBool, MyBool>();
+
+    test_ctor_optional_T_from_empty_optional_T<MyExplicitBool, MyExplicitBool>();
+
+    test_ctor_optional_T_from_empty_optional_T<bool, bool>();
+    test_ctor_optional_T_from_empty_optional_T<Any, Any>();
+
+    test_inplace_tag_constructor<int>();
+    test_inplace_tag_constructor<Any>();
+    test_inplace_tag_constructor<JustDefault>();
+
+    test_ctor_optional_T_from_optional_U<int>(1);
+    test_ctor_optional_T_from_optional_U<long>(1);
+    test_ctor_optional_T_from_optional_U<bool>(MyBool{true});
+    test_ctor_optional_T_from_optional_U<bool>(MyBool{false});
+    test_ctor_optional_T_from_optional_U<MyBool>(true);
+    test_ctor_optional_T_from_optional_U<MyBool>(false);
+    test_ctor_optional_T_from_optional_U<bool>(MyExplicitBool{true});
+    test_ctor_optional_T_from_optional_U<bool>(MyExplicitBool{false});
+    test_ctor_optional_T_from_optional_U<MyExplicitBool>(true);
+    test_ctor_optional_T_from_optional_U<MyExplicitBool>(false);
+    test_ctor_optional_T_from_optional_U<Any>(true);
+    test_ctor_optional_T_from_optional_U<Any>(Any{});
+
+    test_ctor_optional_T_from_valued_optional_T(1);
+
+    optional<MyBool> ob;
+    optional<bool> oa;
+    oa = ob;
+    BOOST_TEST(!oa);
+
+    return boost::report_errors();
+}

test/optional_test_convert_from_T.cpp

@@ -45,6 +45,8 @@ void test_optional_of_superconverting_T() // compile-time test
   superconv<optional<int> > s;
    superconv<optional<int> > & rs = s;
   optional<superconv<optional<int> > > os = rs;
+  (void)s;
+  (void)os;
 #endif
 }
 

test/optional_test_inplace_factory.cpp

@@ -111,10 +111,10 @@ template <typename CharT>
 struct basic_formatter
 {
   template< typename FunT >
-  basic_formatter(FunT&& fun) {}
+  basic_formatter(FunT&&) {}
 
   template< typename FunT >
-  basic_formatter& operator= (FunT&& fun)
+  basic_formatter& operator= (FunT&&)
   {
       return *this;
   }