Disable throws_assign_fail.cpp for GCC/release, because gcc-12 fails it at compile time

.github/workflows/ci.yml

@@ -47,6 +47,10 @@ jobs:
             cxxstd: "03,11,14,17,2a"
             os: ubuntu-20.04
             install: g++-11
+          - toolset: gcc-12
+            cxxstd: "03,11,14,17,20"
+            os: ubuntu-22.04
+            install: g++-12
           - toolset: clang
             compiler: clang++-3.9
             cxxstd: "03,11,14"
@@ -92,8 +96,18 @@ jobs:
             os: ubuntu-20.04
           - toolset: clang
             compiler: clang++-12
-            cxxstd: "03,11,14,17,2a"
+            cxxstd: "03,11,14,17,20"
             os: ubuntu-20.04
+          - toolset: clang
+            compiler: clang++-13
+            cxxstd: "03,11,14,17,20"
+            os: ubuntu-22.04
+            install: clang-13
+          - toolset: clang
+            compiler: clang++-14
+            cxxstd: "03,11,14,17,20"
+            os: ubuntu-22.04
+            install: clang-14
           - toolset: clang
             cxxstd: "03,11,14,17,2a"
             os: macos-10.15
@@ -205,6 +219,7 @@ jobs:
         include:
           - os: ubuntu-18.04
           - os: ubuntu-20.04
+          - os: ubuntu-22.04
           - os: macos-10.15
 
     runs-on: ${{matrix.os}}
@@ -251,6 +266,7 @@ jobs:
         include:
           - os: ubuntu-18.04
           - os: ubuntu-20.04
+          - os: ubuntu-22.04
           - os: macos-10.15
 
     runs-on: ${{matrix.os}}
@@ -307,6 +323,7 @@ jobs:
         include:
           - os: ubuntu-18.04
           - os: ubuntu-20.04
+          - os: ubuntu-22.04
           - os: macos-10.15
 
     runs-on: ${{matrix.os}}

appveyor.yml

@@ -24,10 +24,6 @@ environment:
       TOOLSET: msvc-14.1
       CXXSTD: 14,17,latest
       ADDRMD: 32,64
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
-      TOOLSET: clang-win
-      CXXSTD: 14,17,latest
-      ADDRMD: 32,64
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
       ADDPATH: C:\cygwin\bin;
       TOOLSET: gcc

doc/system/changes.adoc

@@ -8,6 +8,15 @@ https://www.boost.org/LICENSE_1_0.txt
 # Revision History
 :idprefix:
 
+## Changes in Boost 1.80
+
+* When an `error_code` is converted to `std::error_code` and then back
+  to `error_code`, the original is now restored, if possible.
+* Reworked the conversion from `error_category` to `std::error_category`
+  to avoid the one-time allocation that shows up on leak checkers.
+* Added a constructor that allows replacing the source location of an
+  `error_code`, and a corresponding `assign`.
+
 ## Changes in Boost 1.79
 
 * Added a `boost::source_location` parameter to `throw_exception_from_error`.

doc/system/reference.adoc

@@ -610,9 +610,8 @@ public:
     template<class ErrorCodeEnum>
       constexpr error_code( ErrorCodeEnum e ) noexcept;
 
-    template<class ErrorCodeEnum>
-      error_code( ErrorCodeEnum e, boost::source_location const * loc )
-        noexcept;
+    error_code( error_code const& ec,
+      boost::source_location const * loc ) noexcept;
 
     error_code( std::error_code const& ec ) noexcept;
 
@@ -626,9 +625,8 @@ public:
     template<class ErrorCodeEnum>
       constexpr error_code & operator=( ErrorCodeEnum e ) noexcept;
 
-    template<class ErrorCodeEnum>
-      void assign( ErrorCodeEnum e,
-        boost::source_location const * loc ) noexcept;
+    void assign( error_code const& ec,
+      boost::source_location const * loc ) noexcept;
 
     constexpr void clear() noexcept;
 
@@ -757,17 +755,17 @@ Ensures: :: `*this == make_error_code( e )`.
 Remarks: :: This constructor is only enabled when `is_error_code_enum<ErrorCodeEnum>::value` is `true`.
 
 ```
-template<class ErrorCodeEnum>
-  error_code( ErrorCodeEnum e, boost::source_location const * loc ) noexcept;
+error_code( error_code const& ec,
+  boost::source_location const * loc ) noexcept;
 ```
 [none]
 * {blank}
 +
-Requires: :: `loc` points to a valid `boost::source_location` object with static storage duration.
-Ensures: :: `*this == make_error_code( e )`.
-Remarks: :: This constructor is only enabled when `is_error_code_enum<ErrorCodeEnum>::value` is `true`.
-  When `make_error_code( e )` is not a default-constructed `error_code` and doesn't wrap a
-  `std::error_code`, `has_location()` is `true` and `&location()` is `loc`.
+Requires: :: `loc` points to a valid `boost::source_location` object with static storage duration, or is `nullptr`.
+Ensures: :: `*this == ec`.
+Remarks: :: When `ec` is a default-constructed `error_code` or wraps a `std::error_code`,
+  or when `loc` is `nullptr`, `*this` stores no location (`has_location()` is `false`).
+  Otherwise, `*this` stores `loc` (`has_location()` is `true` and `&location()` is `loc`.)
 
 ```
 error_code( std::error_code const & ec ) noexcept;
@@ -808,16 +806,13 @@ Ensures: :: `*this == make_error_code( e )`.
 Remarks: :: This operator is only enabled when `is_error_code_enum<ErrorCodeEnum>::value` is `true`.
 
 ```
-template<class ErrorCodeEnum>
-  void assign( ErrorCodeEnum e,
-    boost::source_location const * loc ) noexcept;
+void assign( error_code const& ec,
+  boost::source_location const * loc ) noexcept;
 ```
 [none]
 * {blank}
 +
-Requires: :: `loc` points to a valid `boost::source_location` object with static storage duration.
-Effects: :: `*this = error_code( e, loc )`.
-Remarks: :: This function is only enabled when `is_error_code_enum<ErrorCodeEnum>::value` is `true`.
+Effects: :: `*this = error_code( ec, loc )`.
 
 ```
 constexpr void clear() noexcept;

include/boost/system/detail/config.hpp

@@ -13,7 +13,7 @@
 
 // BOOST_SYSTEM_HAS_SYSTEM_ERROR
 
-#if !defined(BOOST_NO_CXX11_HDR_SYSTEM_ERROR) && !defined(BOOST_NO_CXX11_HDR_ATOMIC)
+#if !defined(BOOST_NO_CXX11_HDR_SYSTEM_ERROR) && !defined(BOOST_NO_CXX11_HDR_ATOMIC) && !defined(BOOST_NO_CXX11_HDR_MUTEX)
 # define BOOST_SYSTEM_HAS_SYSTEM_ERROR
 #endif
 

include/boost/system/detail/error_category.hpp

@@ -48,6 +48,11 @@ class std_category;
 #pragma GCC diagnostic ignored "-Wnon-virtual-dtor"
 #endif
 
+#if defined(BOOST_MSVC)
+#pragma warning(push)
+#pragma warning(disable: 4351) //  new behavior: elements of array will be default initialized
+#endif
+
 class BOOST_SYMBOL_VISIBLE error_category
 {
 private:
@@ -76,13 +81,21 @@ private:
 
     boost::ulong_long_type id_;
 
+    static std::size_t const stdcat_size_ = 4 * sizeof( void const* );
+
+    union
+    {
+        mutable unsigned char stdcat_[ stdcat_size_ ];
+        void const* stdcat_align_;
+    };
+
 #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
 
-    mutable std::atomic< boost::system::detail::std_category* > ps_;
+    mutable std::atomic< unsigned > sc_init_;
 
 #else
 
-    boost::system::detail::std_category* ps_;
+    unsigned sc_init_;
 
 #endif
 
@@ -103,11 +116,11 @@ protected:
 
 #endif
 
-    BOOST_SYSTEM_CONSTEXPR error_category() BOOST_NOEXCEPT: id_( 0 ), ps_()
+    BOOST_SYSTEM_CONSTEXPR error_category() BOOST_NOEXCEPT: id_( 0 ), stdcat_(), sc_init_()
     {
     }
 
-    explicit BOOST_SYSTEM_CONSTEXPR error_category( boost::ulong_long_type id ) BOOST_NOEXCEPT: id_( id ), ps_()
+    explicit BOOST_SYSTEM_CONSTEXPR error_category( boost::ulong_long_type id ) BOOST_NOEXCEPT: id_( id ), stdcat_(), sc_init_()
     {
     }
 
@@ -158,14 +171,22 @@ public:
     }
 
 #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
+
+    void init_stdcat() const;
+
 # if defined(__SUNPRO_CC) // trailing __global is not supported
     operator std::error_category const & () const;
 # else
     operator std::error_category const & () const BOOST_SYMBOL_VISIBLE;
 # endif
+
 #endif
 };
 
+#if defined(BOOST_MSVC)
+#pragma warning(pop)
+#endif
+
 #if ( defined( BOOST_GCC ) && BOOST_GCC >= 40600 ) || defined( BOOST_CLANG )
 #pragma GCC diagnostic pop
 #endif

include/boost/system/detail/error_category_impl.hpp

@@ -98,25 +98,65 @@ inline char const * error_category::message( int ev, char * buffer, std::size_t
 #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
 
 #include <boost/system/detail/std_category_impl.hpp>
+#include <mutex>
+#include <new>
 
 namespace boost
 {
 namespace system
 {
 
-inline error_category::operator std::error_category const & () const
+namespace detail
+{
+
+template<class = void> struct stdcat_mx_holder
+{
+    static std::mutex mx_;
+};
+
+template<class T> std::mutex stdcat_mx_holder<T>::mx_;
+
+} // namespace detail
+
+inline void error_category::init_stdcat() const
+{
+    static_assert( sizeof( stdcat_ ) >= sizeof( boost::system::detail::std_category ), "sizeof(stdcat_) is not enough for std_category" );
+
+#if defined(BOOST_MSVC) && BOOST_MSVC < 1900
+    // no alignof
+#else
+
+    static_assert( alignof( decltype(stdcat_align_) ) >= alignof( boost::system::detail::std_category ), "alignof(stdcat_) is not enough for std_category" );
+
+#endif
+
+    std::lock_guard<std::mutex> lk( boost::system::detail::stdcat_mx_holder<>::mx_ );
+
+    if( sc_init_.load( std::memory_order_acquire ) == 0 )
+    {
+        ::new( static_cast<void*>( stdcat_ ) ) boost::system::detail::std_category( this, 0 );
+        sc_init_.store( 1, std::memory_order_release );
+    }
+}
+
+#if defined( BOOST_GCC ) && BOOST_GCC >= 40800 && BOOST_GCC < 70000
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wstrict-aliasing"
+#endif
+
+inline BOOST_NOINLINE error_category::operator std::error_category const & () const
 {
     if( id_ == detail::generic_category_id )
     {
 // This condition must be the same as the one in error_condition.hpp
 #if defined(BOOST_SYSTEM_AVOID_STD_GENERIC_CATEGORY)
 
-    static const boost::system::detail::std_category generic_instance( this, 0x1F4D3 );
-    return generic_instance;
+        static const boost::system::detail::std_category generic_instance( this, 0x1F4D3 );
+        return generic_instance;
 
 #else
 
-    return std::generic_category();
+        return std::generic_category();
 
 #endif
     }
@@ -126,49 +166,28 @@ inline error_category::operator std::error_category const & () const
 // This condition must be the same as the one in error_code.hpp
 #if defined(BOOST_SYSTEM_AVOID_STD_SYSTEM_CATEGORY)
 
-    static const boost::system::detail::std_category system_instance( this, 0x1F4D7 );
-    return system_instance;
+        static const boost::system::detail::std_category system_instance( this, 0x1F4D7 );
+        return system_instance;
 
 #else
 
-    return std::system_category();
+        return std::system_category();
 
 #endif
     }
 
-    detail::std_category* p = ps_.load( std::memory_order_acquire );
-
-    if( p != 0 )
+    if( sc_init_.load( std::memory_order_acquire ) == 0 )
     {
-        return *p;
+        init_stdcat();
     }
 
-    // One `std_category` object is allocated for every
-    // user-defined `error_category` that is converted to
-    // `std::error_category`.
-    //
-    // This one-time allocation will show up on leak checkers.
-    // That's unavoidable. There is no way to deallocate the
-    // `std_category` object because first, `error_category`
-    // is a literal type (so it can't have a destructor) and
-    // second, `error_category` needs to be usable during program
-    // shutdown.
-    //
-    // https://github.com/boostorg/system/issues/78
-
-    detail::std_category* q = new detail::std_category( this, 0 );
-
-    if( ps_.compare_exchange_strong( p, q, std::memory_order_release, std::memory_order_acquire ) )
-    {
-        return *q;
-    }
-    else
-    {
-        delete q;
-        return *p;
-    }
+    return *static_cast<boost::system::detail::std_category const*>( static_cast<void const*>( stdcat_ ) );
 }
 
+#if defined( BOOST_GCC ) && BOOST_GCC >= 40800 && BOOST_GCC < 70000
+#pragma GCC diagnostic pop
+#endif
+
 } // namespace system
 } // namespace boost
 

include/boost/system/detail/error_code.hpp

@@ -144,19 +144,14 @@ public:
         *this = make_error_code( e );
     }
 
-    template<class ErrorCodeEnum> error_code( ErrorCodeEnum e, source_location const * loc,
-        typename detail::enable_if<is_error_code_enum<ErrorCodeEnum>::value>::type* = 0 ) BOOST_NOEXCEPT:
+    error_code( error_code const& ec, source_location const * loc ) BOOST_NOEXCEPT:
         d1_(), lc_flags_( 0 )
     {
-        error_code e2 = make_error_code( e );
+        *this = ec;
 
-        if( e2.lc_flags_ == 0 || e2.lc_flags_ == 1 )
+        if( ec.lc_flags_ != 0 && ec.lc_flags_ != 1 )
         {
-            *this = e2;
-        }
-        else
-        {
-            *this = error_code( e2.d1_.val_, *e2.d1_.cat_, loc );
+            lc_flags_ = ( loc? reinterpret_cast<boost::uintptr_t>( loc ): 2 ) | ( ec.lc_flags_ & 1 );
         }
     }
 
@@ -194,6 +189,11 @@ public:
         *this = error_code( val, cat, loc );
     }
 
+    void assign( error_code const& ec, source_location const * loc ) BOOST_NOEXCEPT
+    {
+        *this = error_code( ec, loc );
+    }
+
     template<typename ErrorCodeEnum>
         BOOST_SYSTEM_CONSTEXPR typename detail::enable_if<is_error_code_enum<ErrorCodeEnum>::value, error_code>::type &
         operator=( ErrorCodeEnum val ) BOOST_NOEXCEPT
@@ -202,13 +202,6 @@ public:
         return *this;
     }
 
-    template<typename ErrorCodeEnum>
-        typename detail::enable_if<is_error_code_enum<ErrorCodeEnum>::value, void>::type
-        assign( ErrorCodeEnum val, source_location const * loc ) BOOST_NOEXCEPT
-    {
-        *this = error_code( val, loc );
-    }
-
     BOOST_SYSTEM_CONSTEXPR void clear() BOOST_NOEXCEPT
     {
         *this = error_code();

include/boost/system/result.hpp

@@ -174,6 +174,43 @@ public:
     {
     }
 
+    // converting
+    template<class T2, class E2, class En = typename std::enable_if<
+        std::is_convertible<T2, T>::value &&
+        std::is_convertible<E2, E>::value
+        >::type>
+    BOOST_CXX14_CONSTEXPR result( result<T2, E2> const& r2 )
+        noexcept(
+            std::is_nothrow_constructible<T, T2 const&>::value &&
+            std::is_nothrow_constructible<E, E2>::value &&
+            std::is_nothrow_default_constructible<E2>::value &&
+            std::is_nothrow_copy_constructible<E2>::value )
+        : v_( in_place_error, r2.error() )
+    {
+        if( r2 )
+        {
+            v_.template emplace<0>( *r2 );
+        }
+    }
+
+    template<class T2, class E2, class En = typename std::enable_if<
+        std::is_convertible<T2, T>::value &&
+        std::is_convertible<E2, E>::value
+        >::type>
+    BOOST_CXX14_CONSTEXPR result( result<T2, E2>&& r2 )
+        noexcept(
+            std::is_nothrow_constructible<T, T2&&>::value &&
+            std::is_nothrow_constructible<E, E2>::value &&
+            std::is_nothrow_default_constructible<E2>::value &&
+            std::is_nothrow_copy_constructible<E2>::value )
+        : v_( in_place_error, r2.error() )
+    {
+        if( r2 )
+        {
+            v_.template emplace<0>( std::move( *r2 ) );
+        }
+    }
+
     // queries
 
     constexpr bool has_value() const noexcept

test/CMakeLists.txt

@@ -121,6 +121,9 @@ boost_test(TYPE run SOURCES errc_test4.cpp)
 boost_test(TYPE run SOURCES std_interop_test13.cpp)
 boost_test(TYPE run SOURCES std_interop_test14.cpp)
 
+boost_test(TYPE run SOURCES ec_location_test3.cpp)
+boost_test(TYPE run SOURCES ec_location_test4.cpp)
+
 # result
 
 set(BOOST_TEST_COMPILE_FEATURES cxx_std_11)
@@ -139,3 +142,4 @@ boost_test(TYPE run SOURCES result_eq.cpp)
 boost_test(TYPE run SOURCES result_range_for.cpp)
 boost_test(TYPE run SOURCES result_value_construct2.cpp)
 boost_test(TYPE run SOURCES result_error_construct2.cpp)
+boost_test(TYPE run SOURCES result_convert_construct.cpp)

test/Jamfile.v2

@@ -61,7 +61,11 @@ run single_instance_test.cpp single_instance_lib1 single_instance_lib2 : : : <li
 run single_instance_test.cpp single_instance_lib1 single_instance_lib2 : : : <link>shared : single_instance_lib_shared ;
 
 system-run before_main_test.cpp ;
-run-fail throws_assign_fail.cpp ;
+
+run-fail throws_assign_fail.cpp : : :
+    # GCC 12 catches this at compile time with a warning
+    <toolset>gcc,<variant>release:<build>no ;
+
 system-run constexpr_test.cpp ;
 system-run win32_hresult_test.cpp ;
 
@@ -145,6 +149,9 @@ run errc_test4.cpp ;
 run std_interop_test13.cpp ;
 run std_interop_test14.cpp ;
 
+run ec_location_test3.cpp ;
+run ec_location_test4.cpp ;
+
 # result
 
 import ../../config/checks/config : requires ;
@@ -166,3 +173,4 @@ run result_range_for.cpp : : : $(CPP11) ;
 run result_value_construct2.cpp : : : $(CPP11) ;
 run result_error_construct2.cpp : : : $(CPP11) ;
 run result_errc_construct.cpp : : : $(CPP11) ;
+run result_convert_construct.cpp : : : $(CPP11) ;

test/ec_location_test3.cpp

@@ -0,0 +1,90 @@
+// Copyright 2021, 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/system.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <cerrno>
+
+int main()
+{
+    int const val = ENOENT;
+    boost::system::error_category const & cat = boost::system::generic_category();
+
+    {
+        boost::system::error_code ec;
+
+        BOOST_TEST( !ec.has_location() );
+        BOOST_TEST_EQ( ec.location(), boost::source_location() );
+
+        BOOST_STATIC_CONSTEXPR boost::source_location loc = BOOST_CURRENT_LOCATION;
+
+        boost::system::error_code ec2( ec, &loc );
+
+        BOOST_TEST_EQ( ec2, ec );
+
+        BOOST_TEST( !ec2.has_location() );
+        BOOST_TEST_EQ( ec2.location(), boost::source_location() );
+
+        boost::system::error_code ec3( ec2, 0 );
+
+        BOOST_TEST_EQ( ec3, ec2 );
+
+        BOOST_TEST( !ec3.has_location() );
+        BOOST_TEST_EQ( ec3.location(), boost::source_location() );
+    }
+
+    {
+        boost::system::error_code ec( val, cat );
+
+        BOOST_TEST( !ec.has_location() );
+        BOOST_TEST_EQ( ec.location(), boost::source_location() );
+
+        BOOST_STATIC_CONSTEXPR boost::source_location loc = BOOST_CURRENT_LOCATION;
+
+        boost::system::error_code ec2( ec, &loc );
+
+        BOOST_TEST_EQ( ec2, ec );
+
+        BOOST_TEST( ec2.has_location() );
+        BOOST_TEST_EQ( ec2.location(), loc );
+
+        boost::system::error_code ec3( ec2, 0 );
+
+        BOOST_TEST_EQ( ec3, ec2 );
+
+        BOOST_TEST( !ec3.has_location() );
+        BOOST_TEST_EQ( ec3.location(), boost::source_location() );
+    }
+
+#if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
+
+    {
+        std::error_code e2( val, std::generic_category() );
+
+        boost::system::error_code ec( e2 );
+
+        BOOST_TEST( !ec.has_location() );
+        BOOST_TEST_EQ( ec.location(), boost::source_location() );
+
+        BOOST_STATIC_CONSTEXPR boost::source_location loc = BOOST_CURRENT_LOCATION;
+
+        boost::system::error_code ec2( ec, &loc );
+
+        BOOST_TEST_EQ( ec2, ec );
+
+        BOOST_TEST( !ec2.has_location() );
+        BOOST_TEST_EQ( ec2.location(), boost::source_location() );
+
+        boost::system::error_code ec3( ec2, 0 );
+
+        BOOST_TEST_EQ( ec3, ec2 );
+
+        BOOST_TEST( !ec3.has_location() );
+        BOOST_TEST_EQ( ec3.location(), boost::source_location() );
+    }
+
+#endif
+
+    return boost::report_errors();
+}

test/ec_location_test4.cpp

@@ -0,0 +1,93 @@
+// Copyright 2021, 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/system.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <cerrno>
+
+int main()
+{
+    int const val = ENOENT;
+    boost::system::error_category const & cat = boost::system::generic_category();
+
+    {
+        boost::system::error_code ec;
+        boost::system::error_code ec2( ec );
+
+        BOOST_TEST( !ec.has_location() );
+        BOOST_TEST_EQ( ec.location(), boost::source_location() );
+
+        BOOST_STATIC_CONSTEXPR boost::source_location loc = BOOST_CURRENT_LOCATION;
+
+        ec.assign( ec, &loc );
+
+        BOOST_TEST_EQ( ec, ec2 );
+
+        BOOST_TEST( !ec.has_location() );
+        BOOST_TEST_EQ( ec.location(), boost::source_location() );
+
+        ec.assign( ec, 0 );
+
+        BOOST_TEST_EQ( ec, ec2 );
+
+        BOOST_TEST( !ec.has_location() );
+        BOOST_TEST_EQ( ec.location(), boost::source_location() );
+    }
+
+    {
+        boost::system::error_code ec( val, cat );
+        boost::system::error_code ec2( ec );
+
+        BOOST_TEST( !ec.has_location() );
+        BOOST_TEST_EQ( ec.location(), boost::source_location() );
+
+        BOOST_STATIC_CONSTEXPR boost::source_location loc = BOOST_CURRENT_LOCATION;
+
+        ec.assign( ec, &loc );
+
+        BOOST_TEST_EQ( ec, ec2 );
+
+        BOOST_TEST( ec.has_location() );
+        BOOST_TEST_EQ( ec.location(), loc );
+
+        ec.assign( ec, 0 );
+
+        BOOST_TEST_EQ( ec, ec2 );
+
+        BOOST_TEST( !ec.has_location() );
+        BOOST_TEST_EQ( ec.location(), boost::source_location() );
+    }
+
+#if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
+
+    {
+        std::error_code e2( val, std::generic_category() );
+
+        boost::system::error_code ec( e2 );
+        boost::system::error_code ec2( ec );
+
+        BOOST_TEST( !ec.has_location() );
+        BOOST_TEST_EQ( ec.location(), boost::source_location() );
+
+        BOOST_STATIC_CONSTEXPR boost::source_location loc = BOOST_CURRENT_LOCATION;
+
+        ec.assign( ec, &loc );
+
+        BOOST_TEST_EQ( ec, ec2 );
+
+        BOOST_TEST( !ec.has_location() );
+        BOOST_TEST_EQ( ec.location(), boost::source_location() );
+
+        ec.assign( ec, 0 );
+
+        BOOST_TEST_EQ( ec, ec2 );
+
+        BOOST_TEST( !ec.has_location() );
+        BOOST_TEST_EQ( ec.location(), boost::source_location() );
+    }
+
+#endif
+
+    return boost::report_errors();
+}

test/result_convert_construct.cpp

@@ -0,0 +1,202 @@
+// Copyright 2017, 2021, 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/system/result.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+
+using namespace boost::system;
+
+struct X
+{
+    static int instances;
+
+    int v_;
+
+    X(): v_() { ++instances; }
+
+    X( int v ): v_( v ) { ++instances; }
+
+    X( X const& r ): v_( r.v_ ) { ++instances; }
+
+    X& operator=( X const& ) = delete;
+
+    ~X() { --instances; }
+};
+
+bool operator==( X const & x1, X const & x2 )
+{
+    return x1.v_ == x2.v_;
+}
+
+std::ostream& operator<<( std::ostream& os, X const & x )
+{
+    os << "X:" << x.v_;
+    return os;
+}
+
+int X::instances = 0;
+
+int main()
+{
+    {
+        result<int> r( 5 );
+        result<long> r2 = r;
+
+        BOOST_TEST( r2 ) && BOOST_TEST_EQ( *r2, 5 );
+    }
+
+    {
+        result<int> const r( 6 );
+        result<long> r2 = r;
+
+        BOOST_TEST( r2 ) && BOOST_TEST_EQ( *r2, 6 );
+    }
+
+    {
+        result<long> r2 = result<int>( 7 );
+
+        BOOST_TEST( r2 ) && BOOST_TEST_EQ( *r2, 7 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        result<int> r( 5 );
+        result<X> r2 = r;
+
+        BOOST_TEST( r2 ) && BOOST_TEST_EQ( *r2, 5 );
+        BOOST_TEST_EQ( X::instances, 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        result<int> const r( 6 );
+        result<X> r2 = r;
+
+        BOOST_TEST( r2 ) && BOOST_TEST_EQ( *r2, 6 );
+        BOOST_TEST_EQ( X::instances, 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        result<X> r2 = result<int>( 7 );
+
+        BOOST_TEST( r2 ) && BOOST_TEST_EQ( *r2, 7 );
+        BOOST_TEST_EQ( X::instances, 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        auto ec = make_error_code( errc::invalid_argument );
+
+        result<int> r( ec );
+        result<long> r2 = r;
+
+        BOOST_TEST( !r2 );
+        BOOST_TEST_EQ( r2.error(), ec );
+    }
+
+    {
+        auto ec = make_error_code( errc::invalid_argument );
+
+        result<int> r( ec );
+        result<long> r2 = r;
+
+        BOOST_TEST( !r2 );
+        BOOST_TEST_EQ( r2.error(), ec );
+    }
+
+    {
+        auto ec = make_error_code( errc::invalid_argument );
+
+        result<long> r2 = result<int>( ec );
+
+        BOOST_TEST( !r2 );
+        BOOST_TEST_EQ( r2.error(), ec );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        result<char const*, int> r( "test" );
+        result<std::string, X> r2 = r;
+
+        BOOST_TEST( r2 ) && BOOST_TEST_EQ( *r2, std::string( "test" ) );
+        BOOST_TEST_EQ( X::instances, 0 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        result<char const*, int> const r( "test" );
+        result<std::string, X> r2 = r;
+
+        BOOST_TEST( r2 ) && BOOST_TEST_EQ( *r2, std::string( "test" ) );
+        BOOST_TEST_EQ( X::instances, 0 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        result<std::string, X> r2 = result<char const*, int>( "test" );
+
+        BOOST_TEST( r2 ) && BOOST_TEST_EQ( *r2, std::string( "test" ) );
+        BOOST_TEST_EQ( X::instances, 0 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        result<char const*, int> r( 5 );
+        result<std::string, X> r2 = r;
+
+        BOOST_TEST( !r2 );
+        BOOST_TEST_EQ( r2.error(), X(5) );
+        BOOST_TEST_EQ( X::instances, 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        result<char const*, int> const r( 6 );
+        result<std::string, X> r2 = r;
+
+        BOOST_TEST( !r2 );
+        BOOST_TEST_EQ( r2.error(), X(6) );
+        BOOST_TEST_EQ( X::instances, 1 );
+    }
+
+    {
+        result<std::string, X> r2 = result<char const*, int>( 7 );
+
+        BOOST_TEST( !r2 );
+        BOOST_TEST_EQ( r2.error(), X(7) );
+        BOOST_TEST_EQ( X::instances, 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        BOOST_TEST_TRAIT_TRUE((std::is_constructible<result<long>, result<int>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_convertible<result<int>, result<long>>));
+
+        BOOST_TEST_TRAIT_FALSE((std::is_constructible<result<int>, result<void*>>));
+        BOOST_TEST_TRAIT_FALSE((std::is_convertible<result<void*>, result<int>>));
+
+        BOOST_TEST_TRAIT_FALSE((std::is_constructible<result<int>, result<void>>));
+        BOOST_TEST_TRAIT_FALSE((std::is_convertible<result<void>, result<int>>));
+
+        BOOST_TEST_TRAIT_FALSE((std::is_constructible<result<void>, result<int>>));
+        BOOST_TEST_TRAIT_FALSE((std::is_convertible<result<int>, result<void>>));
+
+        BOOST_TEST_TRAIT_FALSE((std::is_constructible<result<int, void*>, result<int, int>>));
+        BOOST_TEST_TRAIT_FALSE((std::is_convertible<result<int, int>, result<int, void*>>));
+    }
+
+    return boost::report_errors();
+}

test/result_error_construct.cpp

@@ -62,13 +62,13 @@ int main()
         BOOST_TEST( !r.has_value() );
         BOOST_TEST( r.has_error() );
 
-        BOOST_TEST_EQ( r.error(), std::error_code( EINVAL, generic_category() ) );
+        BOOST_TEST_EQ( r.error(), error_code( EINVAL, generic_category() ) );
     }
 
     {
         auto ec = make_error_code( errc::invalid_argument );
 
-        result<std::error_code> r( in_place_error, ec );
+        result<error_code> r( in_place_error, ec );
 
         BOOST_TEST( !r.has_value() );
         BOOST_TEST( r.has_error() );
@@ -77,12 +77,12 @@ int main()
     }
 
     {
-        result<std::error_code> r( in_place_error, EINVAL, generic_category() );
+        result<error_code> r( in_place_error, EINVAL, generic_category() );
 
         BOOST_TEST( !r.has_value() );
         BOOST_TEST( r.has_error() );
 
-        BOOST_TEST_EQ( r.error(), std::error_code( EINVAL, generic_category() ) );
+        BOOST_TEST_EQ( r.error(), error_code( EINVAL, generic_category() ) );
     }
 
     BOOST_TEST_EQ( X::instances, 0 );
@@ -140,8 +140,8 @@ int main()
     BOOST_TEST_EQ( X::instances, 0 );
 
     {
-        BOOST_TEST_TRAIT_TRUE((std::is_constructible<result<int>, std::error_code>));
-        BOOST_TEST_TRAIT_TRUE((std::is_convertible<std::error_code, result<int>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_constructible<result<int>, error_code>));
+        BOOST_TEST_TRAIT_TRUE((std::is_convertible<error_code, result<int>>));
 
         BOOST_TEST_TRAIT_TRUE((std::is_constructible<result<std::string, X>, int>));
         BOOST_TEST_TRAIT_FALSE((std::is_convertible<int, result<std::string, X>>));
@@ -178,7 +178,7 @@ int main()
         BOOST_TEST( !r.has_value() );
         BOOST_TEST( r.has_error() );
 
-        BOOST_TEST_EQ( r.error(), std::error_code( EINVAL, generic_category() ) );
+        BOOST_TEST_EQ( r.error(), error_code( EINVAL, generic_category() ) );
     }
 
     return boost::report_errors();

test/result_error_construct2.cpp

@@ -41,7 +41,7 @@ int main()
         BOOST_TEST( !r.has_value() );
         BOOST_TEST( r.has_error() );
 
-        BOOST_TEST_EQ( r.error(), std::error_code( EINVAL, generic_category() ) );
+        BOOST_TEST_EQ( r.error(), error_code( EINVAL, generic_category() ) );
     }
 
     {