Restore the original system::error_code from std::error_code (refs #79)

Drone config

.drone.jsonnet

@@ -0,0 +1,253 @@
+# Copyright 2022 Peter Dimov
+# Distributed under the Boost Software License, Version 1.0.
+# https://www.boost.org/LICENSE_1_0.txt
+
+local library = "system";
+
+local triggers =
+{
+    branch: [ "master", "develop", "feature/*" ]
+};
+
+local ubsan = { UBSAN: '1', UBSAN_OPTIONS: 'print_stacktrace=1' };
+local asan = { ASAN: '1' };
+
+local linux_pipeline(name, image, environment, packages = "", sources = [], arch = "amd64") =
+{
+    name: name,
+    kind: "pipeline",
+    type: "docker",
+    trigger: triggers,
+    platform:
+    {
+        os: "linux",
+        arch: arch
+    },
+    steps:
+    [
+        {
+            name: "everything",
+            image: image,
+            environment: environment,
+            commands:
+            [
+                'set -e',
+                'wget -O - https://apt.llvm.org/llvm-snapshot.gpg.key | apt-key add -',
+            ] +
+            (if sources != [] then [ ('apt-add-repository "' + source + '"') for source in sources ] else []) +
+            (if packages != "" then [ 'apt-get update', 'apt-get -y install ' + packages ] else []) +
+            [
+                'export LIBRARY=' + library,
+                './.drone/drone.sh',
+            ]
+        }
+    ]
+};
+
+local macos_pipeline(name, environment, xcode_version = "12.2", osx_version = "catalina", arch = "amd64") =
+{
+    name: name,
+    kind: "pipeline",
+    type: "exec",
+    trigger: triggers,
+    platform: {
+        "os": "darwin",
+        "arch": arch
+    },
+    node: {
+        "os": osx_version
+    },
+    steps: [
+        {
+            name: "everything",
+            environment: environment + { "DEVELOPER_DIR": "/Applications/Xcode-" + xcode_version + ".app/Contents/Developer" },
+            commands:
+            [
+                'export LIBRARY=' + library,
+                './.drone/drone.sh',
+            ]
+        }
+    ]
+};
+
+local windows_pipeline(name, image, environment, arch = "amd64") =
+{
+    name: name,
+    kind: "pipeline",
+    type: "docker",
+    trigger: triggers,
+    platform:
+    {
+        os: "windows",
+        arch: arch
+    },
+    "steps":
+    [
+        {
+            name: "everything",
+            image: image,
+            environment: environment,
+            commands:
+            [
+                'cmd /C .drone\\\\drone.bat ' + library,
+            ]
+        }
+    ]
+};
+
+[
+    linux_pipeline(
+        "Linux 14.04 GCC 4.4",
+        "cppalliance/droneubuntu1404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-4.4', CXXSTD: '98,0x' },
+        "g++-4.4",
+        [ "ppa:ubuntu-toolchain-r/test" ],
+    ),
+
+    linux_pipeline(
+        "Linux 14.04 GCC 4.6",
+        "cppalliance/droneubuntu1404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-4.6', CXXSTD: '98,0x' },
+        "g++-4.6",
+        [ "ppa:ubuntu-toolchain-r/test" ],
+    ),
+
+    linux_pipeline(
+        "Linux 14.04 GCC 4.7",
+        "cppalliance/droneubuntu1404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-4.7', CXXSTD: '98,0x' },
+        "g++-4.7",
+        [ "ppa:ubuntu-toolchain-r/test" ],
+    ),
+
+    linux_pipeline(
+        "Linux 14.04 GCC 4.8*",
+        "cppalliance/droneubuntu1404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11' },
+    ),
+
+    linux_pipeline(
+        "Linux 14.04 GCC 4.9",
+        "cppalliance/droneubuntu1404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-4.9', CXXSTD: '03,11' },
+        "g++-4.9",
+        [ "ppa:ubuntu-toolchain-r/test" ],
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 GCC 5*",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14' },
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 GCC 6",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-6', CXXSTD: '03,11,14' },
+        "g++-6",
+    ),
+
+    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",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-8', CXXSTD: '03,11,14,17' },
+        "g++-8",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9* 32",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a', ADDRMD: '32' },
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9* 64",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a', ADDRMD: '64' },
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9 ARM64 32/64",
+        "cppalliance/droneubuntu2004:multiarch",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a', ADDRMD: '32,64' },
+        arch="arm64",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 10 32 ASAN",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-10', CXXSTD: '03,11,14,17,20', ADDRMD: '32' } + asan,
+        "g++-10-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 10 64 ASAN",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-10', CXXSTD: '03,11,14,17,20', ADDRMD: '64' } + asan,
+        "g++-10-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 13",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-13', CXXSTD: '03,11,14,17,20' },
+        "clang-13",
+        ["deb http://apt.llvm.org/focal/ llvm-toolchain-focal-13 main"],
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 14 UBSAN",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-14', CXXSTD: '03,11,14,17,20' } + ubsan,
+        "clang-14",
+        ["deb http://apt.llvm.org/focal/ llvm-toolchain-focal-14 main"],
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 14 ASAN",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-14', CXXSTD: '03,11,14,17,20' } + asan,
+        "clang-14",
+        ["deb http://apt.llvm.org/focal/ llvm-toolchain-focal-14 main"],
+    ),
+
+    macos_pipeline(
+        "MacOS 10.15 Xcode 12.2 UBSAN",
+        { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '03,11,14,1z' } + ubsan,
+    ),
+
+    macos_pipeline(
+        "MacOS 10.15 Xcode 12.2 ASAN",
+        { 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' },
+    ),
+]

.drone/drone.bat

@@ -0,0 +1,23 @@
+@REM Copyright 2022 Peter Dimov
+@REM Distributed under the Boost Software License, Version 1.0.
+@REM https://www.boost.org/LICENSE_1_0.txt
+
+@ECHO ON
+
+set LIBRARY=%1
+set DRONE_BUILD_DIR=%CD%
+
+set BOOST_BRANCH=develop
+if "%DRONE_BRANCH%" == "master" set BOOST_BRANCH=master
+cd ..
+git clone -b %BOOST_BRANCH% --depth 1 https://github.com/boostorg/boost.git boost-root
+cd boost-root
+git submodule update --init tools/boostdep
+xcopy /s /e /q %DRONE_BUILD_DIR% libs\%LIBRARY%\
+python tools/boostdep/depinst/depinst.py %LIBRARY%
+cmd /c bootstrap
+b2 -d0 headers
+
+if not "%CXXSTD%" == "" set CXXSTD=cxxstd=%CXXSTD%
+if not "%ADDRMD%" == "" set ADDRMD=address-model=%ADDRMD%
+b2 -j3 libs/%LIBRARY%/test toolset=%TOOLSET% %CXXSTD% %ADDRMD% variant=debug,release embed-manifest-via=linker

.drone/drone.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+# Copyright 2022 Peter Dimov
+# Distributed under the Boost Software License, Version 1.0.
+# https://www.boost.org/LICENSE_1_0.txt
+
+set -ex
+
+DRONE_BUILD_DIR=$(pwd)
+
+BOOST_BRANCH=develop
+if [ "$DRONE_BRANCH" = "master" ]; then BOOST_BRANCH=master; fi
+
+cd ..
+git clone -b $BOOST_BRANCH --depth 1 https://github.com/boostorg/boost.git boost-root
+cd boost-root
+git submodule update --init tools/boostdep
+cp -r $DRONE_BUILD_DIR/* libs/$LIBRARY
+python tools/boostdep/depinst/depinst.py $LIBRARY
+./bootstrap.sh
+./b2 -d0 headers
+
+echo "using $TOOLSET : : $COMPILER ;" > ~/user-config.jam
+./b2 -j3 libs/$LIBRARY/test toolset=$TOOLSET cxxstd=$CXXSTD variant=debug,release ${ADDRMD:+address-model=$ADDRMD} ${UBSAN:+undefined-sanitizer=norecover debug-symbols=on} ${ASAN:+address-sanitizer=norecover debug-symbols=on} ${LINKFLAGS:+linkflags=$LINKFLAGS}

.github/workflows/ci.yml

@@ -144,15 +144,19 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - toolset: msvc-14.1
-            cxxstd: "14,17,latest"
+          - toolset: msvc-14.0
+            cxxstd: "14"
             addrmd: 32,64
-            os: windows-2016
+            os: windows-2019
           - toolset: msvc-14.2
-            cxxstd: "14,17,latest"
+            cxxstd: "14,17,20,latest"
             addrmd: 32,64
             os: windows-2019
           - toolset: msvc-14.3
+            cxxstd: "14,17,20,latest"
+            addrmd: 32,64
+            os: windows-2022
+          - toolset: clang-win
             cxxstd: "14,17,latest"
             addrmd: 32,64
             os: windows-2022
@@ -192,7 +196,7 @@ jobs:
         shell: cmd
         run: |
           cd ../boost-root
-          b2 -j3 libs/%LIBRARY%/test toolset=${{matrix.toolset}} cxxstd=${{matrix.cxxstd}} address-model=${{matrix.addrmd}} variant=debug,release
+          b2 -j3 libs/%LIBRARY%/test toolset=${{matrix.toolset}} cxxstd=${{matrix.cxxstd}} address-model=${{matrix.addrmd}} variant=debug,release embed-manifest-via=linker
 
   posix-cmake-subdir:
     strategy:

appveyor.yml

@@ -22,20 +22,12 @@ environment:
       ADDRMD: 32,64
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
       TOOLSET: msvc-14.1
-      CXXSTD: 14,17
-      ADDRMD: 32,64
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
-      TOOLSET: clang-win
-      CXXSTD: 14,17
-      ADDRMD: 64
-    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
-      TOOLSET: msvc-14.2
       CXXSTD: 14,17,latest
       ADDRMD: 32,64
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
       TOOLSET: clang-win
       CXXSTD: 14,17,latest
-      ADDRMD: 64
+      ADDRMD: 32,64
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
       ADDPATH: C:\cygwin\bin;
       TOOLSET: gcc

doc/system/changes.adoc

@@ -1,5 +1,5 @@
 ////
-Copyright 2018-2021 Peter Dimov
+Copyright 2018-2022 Peter Dimov
 Distributed under the Boost Software License, Version 1.0.
 https://www.boost.org/LICENSE_1_0.txt
 ////
@@ -8,6 +8,15 @@ https://www.boost.org/LICENSE_1_0.txt
 # Revision History
 :idprefix:
 
+## Changes in Boost 1.79
+
+* Added a `boost::source_location` parameter to `throw_exception_from_error`.
+* Added `throw_exception_from_error` overloads for `errc::errc_t`,
+  `std::error_code`, `std::errc`, `std::exception_ptr`.
+* `result<T>::value` now automatically supplies `BOOST_CURRENT_LOCATION` to
+  `throw_exception_from_error` via a default argument.
+* Added an `errc::make_error_code` overload taking a source location.
+
 ## Changes in Boost 1.78
 
 * Added support for source locations to `error_code`.

doc/system/copyright.adoc

@@ -14,6 +14,6 @@ http://www.boost.org/LICENSE_1_0.txt
 This documentation is
 
 * Copyright 2003-2017 Beman Dawes
-* Copyright 2018-2021 Peter Dimov
+* Copyright 2018-2022 Peter Dimov
 
 and is distributed under the http://www.boost.org/LICENSE_1_0.txt[Boost Software License, Version 1.0].

doc/system/reference.adoc

@@ -1,6 +1,6 @@
 ////
 Copyright 2003-2017 Beman Dawes
-Copyright 2018-2021 Peter Dimov
+Copyright 2018-2022 Peter Dimov
 
 Distributed under the Boost Software License, Version 1.0.
 
@@ -185,9 +185,13 @@ namespace errc {
 template<> struct is_error_condition_enum<errc::errc_t>
   { static const bool value = true; };
 
-constexpr error_code make_error_code( errc::errc_t e ) noexcept;
 constexpr error_condition make_error_condition( errc::errc_t e ) noexcept;
 
+constexpr error_code make_error_code( errc::errc_t e ) noexcept;
+
+error_code make_error_code( errc::errc_t e,
+  boost::source_location const * loc ) noexcept;
+
 } // namespace system
 } // namespace boost
 ```
@@ -256,6 +260,38 @@ void my_api_function( boost::system::error_code& ec )
 }
 ```
 
+```
+constexpr error_code make_error_code( errc::errc_t e,
+  boost::source_location const * loc ) noexcept;
+```
+[none]
+* {blank}
++
+Returns: :: `error_code( e, generic_category(), loc )`.
+
+Same as the above overload, but takes a source location.
+* {blank}
++
+```
+void my_api_function( boost::system::error_code& ec )
+{
+    void* p = std::malloc( 16 );
+
+    if( p == 0 )
+    {
+        // return ENOMEM
+
+        BOOST_STATIC_CONSTEXPR boost::source_location loc =
+          BOOST_CURRENT_LOCATION;
+
+        ec = make_error_code( boost::system::errc::out_of_memory, &loc );
+        return;
+    }
+
+    // use p
+}
+```
+
 ## <boost/system/{zwsp}error_category.hpp>
 
 ### error_category
@@ -1454,7 +1490,20 @@ namespace system {
 
 // throw_exception_from_error
 
-BOOST_NORETURN inline void throw_exception_from_error( error_code const & e );
+BOOST_NORETURN inline void throw_exception_from_error( error_code const & e,
+  boost::source_location const & loc );
+
+BOOST_NORETURN inline void throw_exception_from_error( std::error_code const & e,
+  boost::source_location const & loc );
+
+BOOST_NORETURN inline void throw_exception_from_error( errc::errc_t const & e,
+  boost::source_location const & loc );
+
+BOOST_NORETURN inline void throw_exception_from_error( std::errc const & e,
+  boost::source_location const & loc );
+
+BOOST_NORETURN inline void throw_exception_from_error( std::exception_ptr & e,
+  boost::source_location const & loc );
 
 // in_place_*
 
@@ -1486,13 +1535,57 @@ If `result<T, E>` is used with other error types, the user is expected to provid
 an appropriate overload of `throw_exception_from_error` in the namespace of `E`.
 
 ```
-BOOST_NORETURN inline void throw_exception_from_error( error_code const & e );
+BOOST_NORETURN inline void throw_exception_from_error( error_code const & e,
+  boost::source_location const & loc );
 ```
 [none]
 * {blank}
 +
 Effects: ::
-  `boost::throw_exception( system_error( e ) )`.
+  `boost::throw_with_location( system_error( e ), loc )`.
+
+```
+BOOST_NORETURN inline void throw_exception_from_error( std::error_code const & e,
+  boost::source_location const & loc );
+```
+[none]
+* {blank}
++
+Effects: ::
+  `boost::throw_with_location( std::system_error( e ), loc )`.
+
+```
+BOOST_NORETURN inline void throw_exception_from_error( errc::errc_t const & e,
+  boost::source_location const & loc );
+```
+[none]
+* {blank}
++
+Effects: ::
+  `boost::throw_with_location( system_error( make_error_code( e ) ), loc )`.
+
+```
+BOOST_NORETURN inline void throw_exception_from_error( std::errc const & e,
+  boost::source_location const & loc );
+```
+[none]
+* {blank}
++
+Effects: ::
+  `boost::throw_with_location( std::system_error( make_error_code( e ) ), loc )`.
+
+```
+BOOST_NORETURN inline void throw_exception_from_error( std::exception_ptr & e,
+  boost::source_location const & loc );
+```
+[none]
+* {blank}
++
+Effects: ::
++
+[disc]
+** If `e` isn't null, `std::rethrow_exception( e )`.
+** Otherwise, `boost::throw_with_location( std::bad_exception(), loc )`.
 
 ### result<T, E>
 
@@ -1528,10 +1621,17 @@ public:
 
     // checked value access
 
-    constexpr T& value() & ;
-    constexpr T const& value() const& ;
-    constexpr T&& value() && ;
-    constexpr T const&& value() const&& ;
+    constexpr T& value( boost::source_location const & loc =
+      BOOST_CURRENT_LOCATION ) & ;
+
+    constexpr T const& value( boost::source_location const & loc =
+      BOOST_CURRENT_LOCATION ) const& ;
+
+    constexpr T&& value( boost::source_location const & loc =
+      BOOST_CURRENT_LOCATION ) && ;
+
+    constexpr T const&& value( boost::source_location const & loc =
+      BOOST_CURRENT_LOCATION ) const&& ;
 
     // unchecked value access
 
@@ -1653,10 +1753,17 @@ Returns: ::
 #### Checked Value Access
 
 ```
-constexpr T& value() & ;
-constexpr T const& value() const& ;
-constexpr T&& value() && ;
-constexpr T const&& value() const&& ;
+constexpr T& value(
+  boost::source_location const & loc = BOOST_CURRENT_LOCATION ) & ;
+
+constexpr T const& value(
+  boost::source_location const & loc = BOOST_CURRENT_LOCATION ) const& ;
+
+constexpr T&& value(
+  boost::source_location const & loc = BOOST_CURRENT_LOCATION ) && ;
+
+constexpr T const&& value(
+  boost::source_location const & loc = BOOST_CURRENT_LOCATION ) const&& ;
 ```
 [none]
 * {blank}
@@ -1664,7 +1771,7 @@ constexpr T const&& value() const&& ;
 Effects: ::
   If `*this` holds a value, returns a reference to it. Otherwise,
   calls `throw_exception_from_error`, passing it a reference to
-  the held error.
+  the held error, and `loc`.
 
 #### Unchecked Value Access
 
@@ -1799,7 +1906,8 @@ public:
 
     // checked value access
 
-    constexpr void value() const;
+    constexpr void value( boost::source_location const & loc =
+      BOOST_CURRENT_LOCATION ) const;
 
     // unchecked value access
 
@@ -1912,14 +2020,15 @@ Returns: ::
 #### Checked Value Access
 
 ```
-constexpr void value() const;
+constexpr void value(
+  boost::source_location const & loc = BOOST_CURRENT_LOCATION ) const;
 ```
 [none]
 * {blank}
 +
 Effects: ::
   If `*this` doesn't hold a value, calls `throw_exception_from_error`,
-  passing it a reference to the held error.
+  passing it a reference to the held error, and `loc`.
 
 #### Unchecked Value Access
 

include/boost/system.hpp

@@ -9,8 +9,9 @@
 
 #include <boost/system/error_code.hpp>
 #include <boost/system/system_error.hpp>
+#include <boost/config.hpp>
 
-#if (__cplusplus >= 201103L) || (defined(_MSC_VER) && _MSC_VER >= 1900)
+#if (__cplusplus >= 201103L) && !(defined(BOOST_GCC) && BOOST_GCC < 40800) || (defined(_MSC_VER) && _MSC_VER >= 1900)
 # include <boost/system/result.hpp>
 #endif
 

include/boost/system/detail/config.hpp

@@ -1,7 +1,7 @@
 #ifndef BOOST_SYSTEM_DETAIL_CONFIG_HPP_INCLUDED
 #define BOOST_SYSTEM_DETAIL_CONFIG_HPP_INCLUDED
 
-// Copyright 2018 Peter Dimov
+// Copyright 2018-2022 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)
@@ -62,4 +62,20 @@
 # define BOOST_SYSTEM_CLANG_6
 #endif
 
+//
+
+#if defined(BOOST_LIBSTDCXX_VERSION) && BOOST_LIBSTDCXX_VERSION < 50000
+# define BOOST_SYSTEM_AVOID_STD_GENERIC_CATEGORY
+#endif
+
+#if defined(__CYGWIN__) || defined(__MINGW32__) || (defined(_MSC_VER) && _MSC_VER == 1800) || (defined(BOOST_LIBSTDCXX_VERSION) && BOOST_LIBSTDCXX_VERSION < 90000)
+
+// Under Cygwin (and MinGW!), std::system_category() is POSIX
+// Under VS2013, std::system_category() isn't quite right
+// Under libstdc++ before 7.4, before 8.3, before 9.1, default_error_condition
+// for the system category returns a condition from the system category
+
+# define BOOST_SYSTEM_AVOID_STD_SYSTEM_CATEGORY
+#endif
+
 #endif // BOOST_SYSTEM_DETAIL_CONFIG_HPP_INCLUDED

include/boost/system/detail/error_category_impl.hpp

@@ -14,6 +14,7 @@
 #include <boost/system/detail/error_condition.hpp>
 #include <boost/system/detail/error_code.hpp>
 #include <boost/system/detail/snprintf.hpp>
+#include <boost/system/detail/config.hpp>
 #include <boost/config.hpp>
 #include <string>
 #include <cstring>
@@ -96,7 +97,7 @@ 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.hpp>
+#include <boost/system/detail/std_category_impl.hpp>
 
 namespace boost
 {
@@ -108,7 +109,7 @@ inline 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_GCC) && BOOST_GCC < 50000
+#if defined(BOOST_SYSTEM_AVOID_STD_GENERIC_CATEGORY)
 
     static const boost::system::detail::std_category generic_instance( this, 0x1F4D3 );
     return generic_instance;
@@ -123,10 +124,7 @@ inline error_category::operator std::error_category const & () const
     if( id_ == detail::system_category_id )
     {
 // This condition must be the same as the one in error_code.hpp
-#if defined(__CYGWIN__) || defined(__MINGW32__) || (defined(_MSC_VER) && _MSC_VER == 1800) || (defined(BOOST_GCC) && BOOST_GCC < 50000)
-
-    // Under Cygwin (and MinGW!), std::system_category() is POSIX
-    // Under VS2013, std::system_category() isn't quite right
+#if defined(BOOST_SYSTEM_AVOID_STD_SYSTEM_CATEGORY)
 
     static const boost::system::detail::std_category system_instance( this, 0x1F4D7 );
     return system_instance;
@@ -145,6 +143,19 @@ inline error_category::operator std::error_category const & () const
         return *p;
     }
 
+    // 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 ) )

include/boost/system/detail/error_code.hpp

@@ -21,6 +21,11 @@
 #include <boost/system/detail/append_int.hpp>
 #include <boost/system/detail/snprintf.hpp>
 #include <boost/system/detail/config.hpp>
+
+#if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
+# include <boost/system/detail/std_category.hpp>
+#endif
+
 #include <boost/assert/source_location.hpp>
 #include <boost/cstdint.hpp>
 #include <boost/config.hpp>
@@ -83,6 +88,28 @@ private:
     // >3: pointer to source_location, failed_ in lsb
     boost::uintptr_t lc_flags_;
 
+private:
+
+    char const* category_name() const BOOST_NOEXCEPT
+    {
+        // return category().name();
+
+        if( lc_flags_ == 0 )
+        {
+            // must match detail::system_error_category::name()
+            return "system";
+        }
+        else if( lc_flags_ == 1 )
+        {
+            // must match detail::interop_error_category::name()
+            return "std:unknown";
+        }
+        else
+        {
+            return d1_.cat_->name();
+        }
+    }
+
 public:
 
     // constructors:
@@ -136,9 +163,21 @@ public:
 #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
 
     error_code( std::error_code const& ec ) BOOST_NOEXCEPT:
-        lc_flags_( 1 )
+        d1_(), lc_flags_( 0 )
     {
-        ::new( d2_ ) std::error_code( ec );
+#ifndef BOOST_NO_RTTI
+
+        if( detail::std_category const* pc2 = dynamic_cast< detail::std_category const* >( &ec.category() ) )
+        {
+            *this = boost::system::error_code( ec.value(), pc2->original_category() );
+        }
+        else
+
+#endif
+        {
+            ::new( d2_ ) std::error_code( ec );
+            lc_flags_ = 1;
+        }
     }
 
 #endif
@@ -188,7 +227,11 @@ public:
 #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
 
             std::error_code const& ec = *reinterpret_cast<std::error_code const*>( d2_ );
-            return ec.value() + 1000 * static_cast<unsigned>( reinterpret_cast<boost::uintptr_t>( &ec.category() ) % 2097143 ); // 2^21-9, prime
+
+            unsigned cv = static_cast<unsigned>( ec.value() );
+            unsigned ch = static_cast<unsigned>( reinterpret_cast<boost::uintptr_t>( &ec.category() ) % 2097143 ); // 2^21-9, prime
+
+            return static_cast<int>( cv + 1000 * ch );
 #else
 
             return -1;
@@ -230,7 +273,14 @@ public:
 
 #endif
 
-        return category().message( value() );
+        if( lc_flags_ == 0 )
+        {
+            return detail::system_error_category_message( value() );
+        }
+        else
+        {
+            return category().message( value() );
+        }
     }
 
     char const * message( char * buffer, std::size_t len ) const BOOST_NOEXCEPT
@@ -238,23 +288,33 @@ public:
 #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
         if( lc_flags_ == 1 )
         {
+            std::error_code const& ec = *reinterpret_cast<std::error_code const*>( d2_ );
+
 #if !defined(BOOST_NO_EXCEPTIONS)
             try
 #endif
             {
-                std::error_code const& ec = *reinterpret_cast<std::error_code const*>( d2_ );
                 detail::snprintf( buffer, len, "%s", ec.message().c_str() );
                 return buffer;
             }
 #if !defined(BOOST_NO_EXCEPTIONS)
             catch( ... )
             {
+                detail::snprintf( buffer, len, "No message text available for error std:%s:%d", ec.category().name(), ec.value() );
+                return buffer;
             }
 #endif
         }
 #endif
 
-        return category().message( value(), buffer, len );
+        if( lc_flags_ == 0 )
+        {
+            return detail::system_error_category_message( value(), buffer, len );
+        }
+        else
+        {
+            return category().message( value(), buffer, len );
+        }
     }
 
     BOOST_SYSTEM_CONSTEXPR bool failed() const BOOST_NOEXCEPT
@@ -532,7 +592,7 @@ public:
         else if( lc_flags_ == 0 )
         {
 // This condition must be the same as the one in error_category_impl.hpp
-#if defined(__CYGWIN__) || defined(__MINGW32__) || (defined(_MSC_VER) && _MSC_VER == 1800) || (defined(BOOST_GCC) && BOOST_GCC < 50000)
+#if defined(BOOST_SYSTEM_AVOID_STD_SYSTEM_CATEGORY)
 
             return std::error_code( 0, boost::system::system_category() );
 
@@ -594,7 +654,7 @@ public:
         else
 #endif
         {
-            std::string r = category().name();
+            std::string r = category_name();
             detail::append_int( r, value() );
             return r;
         }
@@ -604,7 +664,7 @@ public:
         inline friend std::basic_ostream<Ch, Tr>&
         operator<< (std::basic_ostream<Ch, Tr>& os, error_code const & ec)
     {
-        return os << ec.to_string();
+        return os << ec.to_string().c_str();
     }
 
     std::string what() const

include/boost/system/detail/error_condition.hpp

@@ -223,7 +223,7 @@ public:
     operator std::error_condition () const
     {
 // This condition must be the same as the one in error_category_impl.hpp
-#if defined(BOOST_GCC) && BOOST_GCC < 50000
+#if defined(BOOST_SYSTEM_AVOID_STD_GENERIC_CATEGORY)
 
         return std::error_condition( value(), category() );
 

include/boost/system/detail/std_category.hpp

@@ -11,9 +11,6 @@
 // See library home page at http://www.boost.org/libs/system
 
 #include <boost/system/detail/error_category.hpp>
-#include <boost/system/detail/error_condition.hpp>
-#include <boost/system/detail/error_code.hpp>
-#include <boost/system/detail/generic_category.hpp>
 #include <system_error>
 
 //
@@ -33,6 +30,13 @@ private:
 
     boost::system::error_category const * pc_;
 
+public:
+
+    boost::system::error_category const & original_category() const BOOST_NOEXCEPT
+    {
+        return *pc_;
+    }
+
 public:
 
     explicit std_category( boost::system::error_category const * pc, unsigned id ): pc_( pc )
@@ -66,72 +70,10 @@ public:
         return pc_->default_error_condition( ev );
     }
 
-    bool equivalent( int code, const std::error_condition & condition ) const BOOST_NOEXCEPT BOOST_OVERRIDE;
-    bool equivalent( const std::error_code & code, int condition ) const BOOST_NOEXCEPT BOOST_OVERRIDE;
+    inline bool equivalent( int code, const std::error_condition & condition ) const BOOST_NOEXCEPT BOOST_OVERRIDE;
+    inline bool equivalent( const std::error_code & code, int condition ) const BOOST_NOEXCEPT BOOST_OVERRIDE;
 };
 
-inline bool std_category::equivalent( int code, const std::error_condition & condition ) const BOOST_NOEXCEPT
-{
-    if( condition.category() == *this )
-    {
-        boost::system::error_condition bn( condition.value(), *pc_ );
-        return pc_->equivalent( code, bn );
-    }
-    else if( condition.category() == std::generic_category() || condition.category() == boost::system::generic_category() )
-    {
-        boost::system::error_condition bn( condition.value(), boost::system::generic_category() );
-        return pc_->equivalent( code, bn );
-    }
-
-#ifndef BOOST_NO_RTTI
-
-    else if( std_category const* pc2 = dynamic_cast< std_category const* >( &condition.category() ) )
-    {
-        boost::system::error_condition bn( condition.value(), *pc2->pc_ );
-        return pc_->equivalent( code, bn );
-    }
-
-#endif
-
-    else
-    {
-        return default_error_condition( code ) == condition;
-    }
-}
-
-inline bool std_category::equivalent( const std::error_code & code, int condition ) const BOOST_NOEXCEPT
-{
-    if( code.category() == *this )
-    {
-        boost::system::error_code bc( code.value(), *pc_ );
-        return pc_->equivalent( bc, condition );
-    }
-    else if( code.category() == std::generic_category() || code.category() == boost::system::generic_category() )
-    {
-        boost::system::error_code bc( code.value(), boost::system::generic_category() );
-        return pc_->equivalent( bc, condition );
-    }
-
-#ifndef BOOST_NO_RTTI
-
-    else if( std_category const* pc2 = dynamic_cast< std_category const* >( &code.category() ) )
-    {
-        boost::system::error_code bc( code.value(), *pc2->pc_ );
-        return pc_->equivalent( bc, condition );
-    }
-
-#endif
-
-    else if( *pc_ == boost::system::generic_category() )
-    {
-        return std::generic_category().equivalent( code, condition );
-    }
-    else
-    {
-        return false;
-    }
-}
-
 } // namespace detail
 
 } // namespace system

include/boost/system/detail/std_category_impl.hpp

@@ -0,0 +1,97 @@
+#ifndef BOOST_SYSTEM_DETAIL_STD_CATEGORY_IMPL_HPP_INCLUDED
+#define BOOST_SYSTEM_DETAIL_STD_CATEGORY_IMPL_HPP_INCLUDED
+
+// Support for interoperability between Boost.System and <system_error>
+//
+// Copyright 2018, 2021 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)
+//
+// See library home page at http://www.boost.org/libs/system
+
+#include <boost/system/detail/std_category.hpp>
+#include <boost/system/detail/error_condition.hpp>
+#include <boost/system/detail/error_code.hpp>
+#include <boost/system/detail/generic_category.hpp>
+
+//
+
+namespace boost
+{
+
+namespace system
+{
+
+namespace detail
+{
+
+inline bool std_category::equivalent( int code, const std::error_condition & condition ) const BOOST_NOEXCEPT
+{
+    if( condition.category() == *this )
+    {
+        boost::system::error_condition bn( condition.value(), *pc_ );
+        return pc_->equivalent( code, bn );
+    }
+    else if( condition.category() == std::generic_category() || condition.category() == boost::system::generic_category() )
+    {
+        boost::system::error_condition bn( condition.value(), boost::system::generic_category() );
+        return pc_->equivalent( code, bn );
+    }
+
+#ifndef BOOST_NO_RTTI
+
+    else if( std_category const* pc2 = dynamic_cast< std_category const* >( &condition.category() ) )
+    {
+        boost::system::error_condition bn( condition.value(), *pc2->pc_ );
+        return pc_->equivalent( code, bn );
+    }
+
+#endif
+
+    else
+    {
+        return default_error_condition( code ) == condition;
+    }
+}
+
+inline bool std_category::equivalent( const std::error_code & code, int condition ) const BOOST_NOEXCEPT
+{
+    if( code.category() == *this )
+    {
+        boost::system::error_code bc( code.value(), *pc_ );
+        return pc_->equivalent( bc, condition );
+    }
+    else if( code.category() == std::generic_category() || code.category() == boost::system::generic_category() )
+    {
+        boost::system::error_code bc( code.value(), boost::system::generic_category() );
+        return pc_->equivalent( bc, condition );
+    }
+
+#ifndef BOOST_NO_RTTI
+
+    else if( std_category const* pc2 = dynamic_cast< std_category const* >( &code.category() ) )
+    {
+        boost::system::error_code bc( code.value(), *pc2->pc_ );
+        return pc_->equivalent( bc, condition );
+    }
+
+#endif
+
+    else if( *pc_ == boost::system::generic_category() )
+    {
+        return std::generic_category().equivalent( code, condition );
+    }
+    else
+    {
+        return false;
+    }
+}
+
+} // namespace detail
+
+} // namespace system
+
+} // namespace boost
+
+#endif // #ifndef BOOST_SYSTEM_DETAIL_STD_CATEGORY_IMPL_HPP_INCLUDED

include/boost/system/detail/system_category_impl.hpp

@@ -11,6 +11,7 @@
 //  See library home page at http://www.boost.org/libs/system
 
 #include <boost/system/detail/system_category.hpp>
+#include <boost/system/detail/system_category_message.hpp>
 #include <boost/system/detail/error_condition.hpp>
 #include <boost/system/api_config.hpp>
 
@@ -22,7 +23,6 @@
 
 #if defined(BOOST_WINDOWS_API)
 
-#include <boost/system/detail/system_category_message_win32.hpp>
 #include <boost/system/detail/system_category_condition_win32.hpp>
 
 inline boost::system::error_condition boost::system::detail::system_error_category::default_error_condition( int ev ) const BOOST_NOEXCEPT
@@ -39,35 +39,23 @@ inline boost::system::error_condition boost::system::detail::system_error_catego
     }
 }
 
-inline std::string boost::system::detail::system_error_category::message( int ev ) const
-{
-    return system_category_message_win32( ev );
-}
-
-inline char const * boost::system::detail::system_error_category::message( int ev, char * buffer, std::size_t len ) const BOOST_NOEXCEPT
-{
-    return system_category_message_win32( ev, buffer, len );
-}
-
 #else // #if defined(BOOST_WINDOWS_API)
 
-#include <boost/system/detail/generic_category_message.hpp>
-
 inline boost::system::error_condition boost::system::detail::system_error_category::default_error_condition( int ev ) const BOOST_NOEXCEPT
 {
     return error_condition( boost::system::detail::generic_value_tag( ev ) );
 }
 
+#endif // #if defined(BOOST_WINDOWS_API)
+
 inline std::string boost::system::detail::system_error_category::message( int ev ) const
 {
-    return generic_error_category_message( ev );
+    return system_error_category_message( ev );
 }
 
 inline char const * boost::system::detail::system_error_category::message( int ev, char * buffer, std::size_t len ) const BOOST_NOEXCEPT
 {
-    return generic_error_category_message( ev, buffer, len );
+    return system_error_category_message( ev, buffer, len );
 }
 
-#endif // #if defined(BOOST_WINDOWS_API)
-
 #endif // #ifndef BOOST_SYSTEM_DETAIL_SYSTEM_CATEGORY_IMPL_HPP_INCLUDED

include/boost/system/detail/system_category_message.hpp

@@ -0,0 +1,71 @@
+#ifndef BOOST_SYSTEM_DETAIL_SYSTEM_CATEGORY_MESSAGE_HPP_INCLUDED
+#define BOOST_SYSTEM_DETAIL_SYSTEM_CATEGORY_MESSAGE_HPP_INCLUDED
+
+// Implementation of system_error_category_message
+//
+// Copyright 2018, 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)
+//
+// See library home page at http://www.boost.org/libs/system
+
+#include <boost/system/api_config.hpp>
+
+#if !defined(BOOST_POSIX_API) && !defined(BOOST_WINDOWS_API)
+#  error BOOST_POSIX_API or BOOST_WINDOWS_API must be defined
+#endif
+
+#if defined(BOOST_WINDOWS_API)
+
+#include <boost/system/detail/system_category_message_win32.hpp>
+
+namespace boost
+{
+namespace system
+{
+namespace detail
+{
+
+inline std::string system_error_category_message( int ev )
+{
+    return system_category_message_win32( ev );
+}
+
+inline char const * system_error_category_message( int ev, char * buffer, std::size_t len ) BOOST_NOEXCEPT
+{
+    return system_category_message_win32( ev, buffer, len );
+}
+
+} // namespace detail
+} // namespace system
+} // namespace boost
+
+#else // #if defined(BOOST_WINDOWS_API)
+
+#include <boost/system/detail/generic_category_message.hpp>
+
+namespace boost
+{
+namespace system
+{
+namespace detail
+{
+
+inline std::string system_error_category_message( int ev )
+{
+    return generic_error_category_message( ev );
+}
+
+inline char const * system_error_category_message( int ev, char * buffer, std::size_t len ) BOOST_NOEXCEPT
+{
+    return generic_error_category_message( ev, buffer, len );
+}
+
+} // namespace detail
+} // namespace system
+} // namespace boost
+
+#endif // #if defined(BOOST_WINDOWS_API)
+
+#endif // #ifndef BOOST_SYSTEM_DETAIL_SYSTEM_CATEGORY_MESSAGE_HPP_INCLUDED

include/boost/system/errc.hpp

@@ -16,6 +16,7 @@
 #include <boost/system/detail/generic_category.hpp>
 #include <boost/system/detail/error_category_impl.hpp>
 #include <boost/system/detail/config.hpp>
+#include <boost/assert/source_location.hpp>
 #include <boost/config.hpp>
 
 namespace boost
@@ -35,6 +36,12 @@ BOOST_SYSTEM_CONSTEXPR inline error_code make_error_code( errc_t e ) BOOST_NOEXC
     return error_code( e, generic_category() );
 }
 
+// explicit conversion:
+inline error_code make_error_code( errc_t e, boost::source_location const * loc ) BOOST_NOEXCEPT
+{
+    return error_code( e, generic_category(), loc );
+}
+
 // implicit conversion:
 BOOST_SYSTEM_CONSTEXPR inline error_condition make_error_condition( errc_t e ) BOOST_NOEXCEPT
 {

include/boost/system/linux_error.hpp

@@ -10,13 +10,6 @@
 #ifndef BOOST_SYSTEM_LINUX_ERROR_HPP
 #define BOOST_SYSTEM_LINUX_ERROR_HPP
 
-#include <boost/config/pragma_message.hpp>
-
-#if !defined(BOOST_ALLOW_DEPRECATED_HEADERS)
-  BOOST_PRAGMA_MESSAGE("This header is deprecated and is slated for removal."
-  " If you want it retained, please open an issue in github.com/boostorg/system.")
-#endif
-
 //  This header is effectively empty for compiles on operating systems where
 //  it is not applicable.
 

include/boost/system/result.hpp

@@ -1,7 +1,7 @@
 #ifndef BOOST_SYSTEM_RESULT_HPP_INCLUDED
 #define BOOST_SYSTEM_RESULT_HPP_INCLUDED
 
-// Copyright 2017, 2021 Peter Dimov.
+// Copyright 2017, 2021, 2022 Peter Dimov.
 // Distributed under the Boost Software License, Version 1.0.
 // https://www.boost.org/LICENSE_1_0.txt
 
@@ -11,11 +11,14 @@
 #include <boost/system/detail/error_category_impl.hpp>
 #include <boost/variant2/variant.hpp>
 #include <boost/throw_exception.hpp>
+#include <boost/assert/source_location.hpp>
 #include <boost/assert.hpp>
 #include <boost/config.hpp>
 #include <type_traits>
 #include <utility>
 #include <iosfwd>
+#include <system_error>
+#include <exception>
 
 //
 
@@ -26,11 +29,47 @@ namespace system
 
 // throw_exception_from_error
 
-BOOST_NORETURN inline void throw_exception_from_error( error_code const & e )
+#if defined(__GNUC__) && __GNUC__ >= 7 && __GNUC__ <= 8
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wattributes"
+#endif
+
+BOOST_NORETURN BOOST_NOINLINE inline void throw_exception_from_error( error_code const & e, boost::source_location const& loc )
 {
-    boost::throw_exception( system_error( e ) );
+    boost::throw_with_location( system_error( e ), loc );
 }
 
+BOOST_NORETURN BOOST_NOINLINE inline void throw_exception_from_error( errc::errc_t const & e, boost::source_location const& loc )
+{
+    boost::throw_with_location( system_error( make_error_code( e ) ), loc );
+}
+
+BOOST_NORETURN BOOST_NOINLINE inline void throw_exception_from_error( std::error_code const & e, boost::source_location const& loc )
+{
+    boost::throw_with_location( std::system_error( e ), loc );
+}
+
+BOOST_NORETURN BOOST_NOINLINE inline void throw_exception_from_error( std::errc const & e, boost::source_location const& loc )
+{
+    boost::throw_with_location( std::system_error( make_error_code( e ) ), loc );
+}
+
+BOOST_NORETURN BOOST_NOINLINE inline void throw_exception_from_error( std::exception_ptr const & p, boost::source_location const& loc )
+{
+    if( p )
+    {
+        std::rethrow_exception( p );
+    }
+    else
+    {
+        boost::throw_with_location( std::bad_exception(), loc );
+    }
+}
+
+#if defined(__GNUC__) && __GNUC__ >= 7 && __GNUC__ <= 8
+# pragma GCC diagnostic pop
+#endif
+
 // in_place_*
 
 using in_place_value_t = variant2::in_place_index_t<0>;
@@ -39,6 +78,15 @@ constexpr in_place_value_t in_place_value{};
 using in_place_error_t = variant2::in_place_index_t<1>;
 constexpr in_place_error_t in_place_error{};
 
+namespace detail
+{
+
+template<class T> using remove_cvref = typename std::remove_cv< typename std::remove_reference<T>::type >::type;
+
+template<class... T> using is_errc_t = std::is_same<mp11::mp_list<remove_cvref<T>...>, mp11::mp_list<errc::errc_t>>;
+
+} // namespace detail
+
 // result
 
 template<class T, class E = error_code> class result
@@ -65,6 +113,7 @@ public:
     // implicit, value
     template<class A = T, typename std::enable_if<
         std::is_convertible<A, T>::value &&
+        !(detail::is_errc_t<A>::value && std::is_arithmetic<T>::value) &&
         !std::is_constructible<E, A>::value, int>::type = 0>
     constexpr result( A&& a )
         noexcept( std::is_nothrow_constructible<T, A>::value )
@@ -85,6 +134,7 @@ public:
     // explicit, value
     template<class... A, class En = typename std::enable_if<
         std::is_constructible<T, A...>::value &&
+        !(detail::is_errc_t<A...>::value && std::is_arithmetic<T>::value) &&
         !std::is_constructible<E, A...>::value
         >::type>
     explicit constexpr result( A&&... a )
@@ -144,7 +194,7 @@ public:
     // checked value access
 #if defined( BOOST_NO_CXX11_REF_QUALIFIERS )
 
-    BOOST_CXX14_CONSTEXPR T value() const
+    BOOST_CXX14_CONSTEXPR T value( boost::source_location const& loc = BOOST_CURRENT_LOCATION ) const
     {
         if( has_value() )
         {
@@ -152,13 +202,13 @@ public:
         }
         else
         {
-            throw_exception_from_error( variant2::unsafe_get<1>( v_ ) );
+            throw_exception_from_error( variant2::unsafe_get<1>( v_ ), loc );
         }
     }
 
 #else
 
-    BOOST_CXX14_CONSTEXPR T& value() &
+    BOOST_CXX14_CONSTEXPR T& value( boost::source_location const& loc = BOOST_CURRENT_LOCATION ) &
     {
         if( has_value() )
         {
@@ -166,11 +216,11 @@ public:
         }
         else
         {
-            throw_exception_from_error( variant2::unsafe_get<1>( v_ ) );
+            throw_exception_from_error( variant2::unsafe_get<1>( v_ ), loc );
         }
     }
 
-    BOOST_CXX14_CONSTEXPR T const& value() const&
+    BOOST_CXX14_CONSTEXPR T const& value( boost::source_location const& loc = BOOST_CURRENT_LOCATION ) const&
     {
         if( has_value() )
         {
@@ -178,24 +228,24 @@ public:
         }
         else
         {
-            throw_exception_from_error( variant2::unsafe_get<1>( v_ ) );
+            throw_exception_from_error( variant2::unsafe_get<1>( v_ ), loc );
         }
     }
 
     template<class U = T>
         BOOST_CXX14_CONSTEXPR
         typename std::enable_if<std::is_move_constructible<U>::value, T>::type
-        value() &&
+        value( boost::source_location const& loc = BOOST_CURRENT_LOCATION ) &&
     {
-        return std::move( value() );
+        return std::move( value( loc ) );
     }
 
     template<class U = T>
         BOOST_CXX14_CONSTEXPR
         typename std::enable_if<!std::is_move_constructible<U>::value, T&&>::type
-        value() &&
+        value( boost::source_location const& loc = BOOST_CURRENT_LOCATION ) &&
     {
-        return std::move( value() );
+        return std::move( value( loc ) );
     }
 
     template<class U = T>
@@ -206,9 +256,9 @@ public:
     template<class U = T>
         BOOST_CXX14_CONSTEXPR
         typename std::enable_if<!std::is_move_constructible<U>::value, T const&&>::type
-        value() const &&
+        value( boost::source_location const& loc = BOOST_CURRENT_LOCATION ) const &&
     {
-        return std::move( value() );
+        return std::move( value( loc ) );
     }
 
 #endif
@@ -432,14 +482,14 @@ public:
 
     // checked value access
 
-    BOOST_CXX14_CONSTEXPR void value() const
+    BOOST_CXX14_CONSTEXPR void value( boost::source_location const& loc = BOOST_CURRENT_LOCATION ) const
     {
         if( has_value() )
         {
         }
         else
         {
-            throw_exception_from_error( variant2::unsafe_get<1>( v_ ) );
+            throw_exception_from_error( variant2::unsafe_get<1>( v_ ), loc );
         }
     }
 

include/boost/system/system_error.hpp

@@ -23,46 +23,25 @@ private:
 
     error_code code_;
 
-private:
-
-    static std::string build_message( char const * prefix, error_code const & ec )
-    {
-        std::string r;
-
-        if( prefix )
-        {
-            r += prefix;
-            r += ": ";
-        }
-
-        r += ec.what();
-        return r;
-    }
-
-    static std::string build_message( char const * prefix, int ev, error_category const & cat )
-    {
-        return build_message( prefix, error_code( ev, cat ) );
-    }
-
 public:
 
-    explicit system_error( error_code const & ec )
-      : std::runtime_error( build_message( 0, ec ) ), code_( ec ) {}
+    explicit system_error( error_code const & ec ):
+        std::runtime_error( ec.what() ), code_( ec ) {}
 
-    system_error( error_code const & ec, std::string const & prefix )
-      : std::runtime_error( build_message( prefix.c_str(), ec ) ), code_( ec ) {}
+    system_error( error_code const & ec, std::string const & prefix ):
+        std::runtime_error( prefix + ": " + ec.what() ), code_( ec ) {}
 
-    system_error( error_code const & ec, char const * prefix )
-      : std::runtime_error( build_message( prefix, ec ) ), code_( ec ) {}
+    system_error( error_code const & ec, char const * prefix ):
+        std::runtime_error( std::string( prefix ) + ": " + ec.what() ), code_( ec ) {}
 
-    system_error( int ev, error_category const & ecat )
-      : std::runtime_error( build_message( 0, ev, ecat ) ), code_( ev, ecat ) {}
+    system_error( int ev, error_category const & ecat ):
+        std::runtime_error( error_code( ev, ecat ).what() ), code_( ev, ecat ) {}
 
-    system_error( int ev, error_category const & ecat, std::string const & prefix )
-      : std::runtime_error( build_message( prefix.c_str(), ev, ecat ) ), code_( ev, ecat ) {}
+    system_error( int ev, error_category const & ecat, std::string const & prefix ):
+        std::runtime_error( prefix + ": " + error_code( ev, ecat ).what() ), code_( ev, ecat ) {}
 
-    system_error( int ev, error_category const & ecat, char const * prefix )
-      : std::runtime_error( build_message( prefix, ev, ecat ) ), code_( ev, ecat ) {}
+    system_error( int ev, error_category const & ecat, char const * prefix ):
+        std::runtime_error( std::string( prefix ) + ": " + error_code( ev, ecat ).what() ), code_( ev, ecat ) {}
 
     error_code code() const BOOST_NOEXCEPT
     {

test/CMakeLists.txt

@@ -112,6 +112,15 @@ boost_test(TYPE run SOURCES system_error_test3.cpp)
 
 boost_test(TYPE run SOURCES std_interop_test11.cpp)
 
+boost_test(TYPE run SOURCES ec_wstream_test.cpp)
+
+boost_test(TYPE run SOURCES std_interop_test12.cpp)
+
+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)
+
 # result
 
 set(BOOST_TEST_COMPILE_FEATURES cxx_std_11)

test/Jamfile.v2

@@ -20,6 +20,8 @@ project
     <toolset>msvc:<warnings-as-errors>on
     <toolset>gcc:<warnings-as-errors>on
     <toolset>clang:<warnings-as-errors>on
+
+    <toolset>gcc-4.4:<cxxflags>-Wno-sign-compare
   ;
 
 rule system-run ( sources + )
@@ -134,11 +136,20 @@ run system_error_test3.cpp ;
 
 run std_interop_test11.cpp ;
 
+run ec_wstream_test.cpp ;
+
+run std_interop_test12.cpp ;
+
+run errc_test4.cpp ;
+
+run std_interop_test13.cpp ;
+run std_interop_test14.cpp ;
+
 # result
 
 import ../../config/checks/config : requires ;
 
-CPP11 = [ requires cxx11_variadic_templates cxx11_template_aliases cxx11_decltype cxx11_constexpr cxx11_noexcept ] ;
+CPP11 = [ requires cxx11_variadic_templates cxx11_template_aliases cxx11_decltype cxx11_constexpr cxx11_noexcept ] <toolset>gcc-4.7:<build>no ;
 
 run result_default_construct.cpp : : : $(CPP11) ;
 run result_value_construct.cpp : : : $(CPP11) ;
@@ -154,3 +165,4 @@ run result_eq.cpp : : : $(CPP11) ;
 run result_range_for.cpp : : : $(CPP11) ;
 run result_value_construct2.cpp : : : $(CPP11) ;
 run result_error_construct2.cpp : : : $(CPP11) ;
+run result_errc_construct.cpp : : : $(CPP11) ;

test/ec_wstream_test.cpp

@@ -0,0 +1,21 @@
+// Copyright 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// http://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/system/error_code.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <sstream>
+
+namespace sys = boost::system;
+
+int main()
+{
+    {
+        std::wostringstream os;
+        os << sys::error_code();
+
+        BOOST_TEST( os.str() == L"system:0" );
+    }
+
+    return boost::report_errors();
+}

test/errc_test4.cpp

@@ -0,0 +1,17 @@
+// Copyright 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// http://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/system/errc.hpp>
+#include <boost/assert/source_location.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+int main()
+{
+    BOOST_STATIC_CONSTEXPR boost::source_location loc = BOOST_CURRENT_LOCATION;
+
+    BOOST_TEST( make_error_code( boost::system::errc::no_such_file_or_directory, &loc ).has_location() );
+    BOOST_TEST_EQ( make_error_code( boost::system::errc::no_such_file_or_directory, &loc ).location().to_string(), loc.to_string() );
+
+    return boost::report_errors();
+}

test/result_errc_construct.cpp

@@ -0,0 +1,23 @@
+// Copyright 2021 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_trait.hpp>
+#include <type_traits>
+
+using namespace boost::system;
+
+int main()
+{
+    BOOST_TEST_TRAIT_FALSE((std::is_convertible<errc::errc_t, result<int>>));
+    BOOST_TEST_TRAIT_FALSE((std::is_constructible<result<int>, errc::errc_t>));
+
+    BOOST_TEST_TRAIT_FALSE((std::is_convertible<errc::errc_t, result<double>>));
+    BOOST_TEST_TRAIT_FALSE((std::is_constructible<result<double>, errc::errc_t>));
+
+    BOOST_TEST_TRAIT_FALSE((std::is_convertible<errc::errc_t, result<bool>>));
+    BOOST_TEST_TRAIT_FALSE((std::is_constructible<result<bool>, errc::errc_t>));
+
+    return boost::report_errors();
+}

test/result_value_access.cpp

@@ -1,10 +1,11 @@
-// Copyright 2017, 2021 Peter Dimov.
+// 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>
+#include <system_error>
 
 using namespace boost::system;
 
@@ -26,11 +27,15 @@ struct E
 {
 };
 
-BOOST_NORETURN void throw_exception_from_error( Y const & )
+BOOST_NORETURN void throw_exception_from_error( Y const &, boost::source_location const& )
 {
     throw E();
 }
 
+struct E2
+{
+};
+
 int main()
 {
     {
@@ -165,6 +170,78 @@ int main()
         BOOST_TEST_EQ( result<int>( ec ).operator->(), static_cast<int*>(0) );
     }
 
+    {
+        auto ec = make_error_code( std::errc::invalid_argument );
+
+        result<int, std::error_code> const r( ec );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_NOT( r );
+        BOOST_TEST( !r );
+
+        BOOST_TEST_THROWS( r.value(), std::system_error );
+
+        BOOST_TEST_EQ( r.operator->(), static_cast<int*>(0) );
+    }
+
+    {
+        result<int, errc::errc_t> const r( in_place_error, errc::invalid_argument );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_NOT( r );
+        BOOST_TEST( !r );
+
+        BOOST_TEST_THROWS( r.value(), system_error );
+
+        BOOST_TEST_EQ( r.operator->(), static_cast<int*>(0) );
+    }
+
+    {
+        result<int, std::errc> const r( std::errc::invalid_argument );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_NOT( r );
+        BOOST_TEST( !r );
+
+        BOOST_TEST_THROWS( r.value(), std::system_error );
+
+        BOOST_TEST_EQ( r.operator->(), static_cast<int*>(0) );
+    }
+
+    {
+        result<int, std::exception_ptr> const r( std::make_exception_ptr( E2() ) );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_NOT( r );
+        BOOST_TEST( !r );
+
+        BOOST_TEST_THROWS( r.value(), E2 );
+
+        BOOST_TEST_EQ( r.operator->(), static_cast<int*>(0) );
+    }
+
+    {
+        result<int, std::exception_ptr> const r( in_place_error );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_NOT( r );
+        BOOST_TEST( !r );
+
+        BOOST_TEST_THROWS( r.value(), std::bad_exception );
+
+        BOOST_TEST_EQ( r.operator->(), static_cast<int*>(0) );
+    }
+
     {
         result<X> r( 1 );
 
@@ -341,5 +418,77 @@ int main()
         BOOST_TEST_EQ( result<void>( ec ).operator->(), static_cast<void*>(0) );
     }
 
+    {
+        auto ec = make_error_code( std::errc::invalid_argument );
+
+        result<void, std::error_code> const r( ec );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_NOT( r );
+        BOOST_TEST( !r );
+
+        BOOST_TEST_THROWS( r.value(), std::system_error );
+
+        BOOST_TEST_EQ( r.operator->(), static_cast<void*>(0) );
+    }
+
+    {
+        result<void, errc::errc_t> const r( in_place_error, errc::invalid_argument );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_NOT( r );
+        BOOST_TEST( !r );
+
+        BOOST_TEST_THROWS( r.value(), system_error );
+
+        BOOST_TEST_EQ( r.operator->(), static_cast<void*>(0) );
+    }
+
+    {
+        result<void, std::errc> const r( std::errc::invalid_argument );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_NOT( r );
+        BOOST_TEST( !r );
+
+        BOOST_TEST_THROWS( r.value(), std::system_error );
+
+        BOOST_TEST_EQ( r.operator->(), static_cast<void*>(0) );
+    }
+
+    {
+        result<void, std::exception_ptr> const r( std::make_exception_ptr( E2() ) );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_NOT( r );
+        BOOST_TEST( !r );
+
+        BOOST_TEST_THROWS( r.value(), E2 );
+
+        BOOST_TEST_EQ( r.operator->(), static_cast<void*>(0) );
+    }
+
+    {
+        result<void, std::exception_ptr> const r( in_place_error );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_NOT( r );
+        BOOST_TEST( !r );
+
+        BOOST_TEST_THROWS( r.value(), std::bad_exception );
+
+        BOOST_TEST_EQ( r.operator->(), static_cast<void*>(0) );
+    }
+
     return boost::report_errors();
 }

test/std_interop_test12.cpp

@@ -0,0 +1,127 @@
+// Copyright 2021, 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// http://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/system/error_code.hpp>
+#include <boost/system/error_category.hpp>
+#include <boost/system/errc.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/config/pragma_message.hpp>
+#include <boost/config.hpp>
+#include <cerrno>
+
+#if !defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
+
+BOOST_PRAGMA_MESSAGE( "BOOST_SYSTEM_HAS_SYSTEM_ERROR not defined, test will be skipped" )
+int main() {}
+
+#else
+
+#include <system_error>
+
+enum my_errc
+{
+    my_enoent = ENOENT
+};
+
+class my_category: public boost::system::error_category
+{
+public:
+
+    char const* name() const BOOST_NOEXCEPT
+    {
+        return "mycat";
+    }
+
+    boost::system::error_condition default_error_condition( int ev ) const BOOST_NOEXCEPT
+    {
+        switch( ev )
+        {
+        case my_enoent:
+
+            return boost::system::error_condition( ENOENT, boost::system::generic_category() );
+
+        default:
+
+            return boost::system::error_condition( ev, *this );
+        }
+    }
+
+    std::string message( int ev ) const
+    {
+        switch( ev )
+        {
+        case my_enoent:
+
+            return "No such entity";
+
+        default:
+
+            return "Unknown error";
+        }
+    }
+};
+
+#if defined(BOOST_GCC) && BOOST_GCC < 70000
+
+// g++ 6 and earlier do not allow specializations outside the namespace
+
+namespace boost
+{
+namespace system
+{
+
+template<> struct is_error_code_enum<my_errc>: std::true_type {};
+
+} // namespace system
+} // namespace boost
+
+namespace std
+{
+
+template<> struct is_error_code_enum<my_errc>: std::true_type {};
+
+} // namespace std
+
+#else
+
+template<> struct boost::system::is_error_code_enum<my_errc>: std::true_type {};
+template<> struct std::is_error_code_enum<my_errc>: std::true_type {};
+
+#endif
+
+boost::system::error_code make_error_code( my_errc e )
+{
+    // If `cat` is declared constexpr or const, msvc-14.1 and
+    // msvc-14.2 before 19.29 put it in read-only memory,
+    // despite the `ps_` member being mutable. So it crashes.
+
+    static /*BOOST_SYSTEM_CONSTEXPR*/ my_category cat;
+    return boost::system::error_code( e, cat );
+}
+
+int main()
+{
+    {
+        boost::system::error_code e1 = my_enoent;
+
+        BOOST_TEST( e1 == my_enoent );
+        BOOST_TEST_NOT( e1 != my_enoent );
+
+        BOOST_TEST( e1 == boost::system::errc::no_such_file_or_directory );
+        BOOST_TEST( e1 == std::errc::no_such_file_or_directory );
+    }
+
+    {
+        std::error_code e1 = my_enoent;
+
+        BOOST_TEST( e1 == my_enoent );
+        BOOST_TEST_NOT( e1 != my_enoent );
+
+        BOOST_TEST( e1 == std::errc::no_such_file_or_directory );
+    }
+
+    return boost::report_errors();
+}
+
+#endif

test/std_interop_test13.cpp

@@ -0,0 +1,77 @@
+// Copyright 2021, 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// http://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/system/error_code.hpp>
+#include <boost/system/error_category.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/config/pragma_message.hpp>
+#include <boost/config.hpp>
+#include <cerrno>
+
+#if !defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
+
+BOOST_PRAGMA_MESSAGE( "BOOST_SYSTEM_HAS_SYSTEM_ERROR not defined, test will be skipped" )
+int main() {}
+
+#else
+
+#include <system_error>
+
+class my_category_impl: public std::error_category
+{
+public:
+
+    char const* name() const BOOST_NOEXCEPT
+    {
+        return "mycat";
+    }
+
+    std::string message( int /*ev*/ ) const
+    {
+        return "Unknown error";
+    }
+};
+
+std::error_category const& my_category()
+{
+    static my_category_impl mycat;
+    return mycat;
+}
+
+int main()
+{
+    {
+        std::error_code e1( 5, boost::system::system_category() );
+        boost::system::error_code e2( e1 );
+        std::error_code e3( e2 );
+
+        BOOST_TEST_EQ( e1, e3 );
+        BOOST_TEST_EQ( e1.value(), e3.value() );
+        BOOST_TEST_EQ( &e1.category(), &e3.category() );
+    }
+
+    {
+        std::error_code e1( 5, boost::system::generic_category() );
+        boost::system::error_code e2( e1 );
+        std::error_code e3( e2 );
+
+        BOOST_TEST_EQ( e1, e3 );
+        BOOST_TEST_EQ( e1.value(), e3.value() );
+        BOOST_TEST_EQ( &e1.category(), &e3.category() );
+    }
+
+    {
+        std::error_code e1( 5, my_category() );
+        boost::system::error_code e2( e1 );
+        std::error_code e3( e2 );
+
+        BOOST_TEST_EQ( e1, e3 );
+        BOOST_TEST_EQ( e1.value(), e3.value() );
+        BOOST_TEST_EQ( &e1.category(), &e3.category() );
+    }
+
+    return boost::report_errors();
+}
+
+#endif

test/std_interop_test14.cpp

@@ -0,0 +1,57 @@
+// Copyright 2021, 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// http://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/system/error_code.hpp>
+#include <boost/system/error_category.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/config/pragma_message.hpp>
+#include <boost/config.hpp>
+#include <cerrno>
+
+#if !defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
+
+BOOST_PRAGMA_MESSAGE( "BOOST_SYSTEM_HAS_SYSTEM_ERROR not defined, test will be skipped" )
+int main() {}
+
+#else
+
+#include <system_error>
+
+class my_category_impl: public boost::system::error_category
+{
+public:
+
+    char const* name() const BOOST_NOEXCEPT
+    {
+        return "mycat";
+    }
+
+    std::string message( int /*ev*/ ) const
+    {
+        return "Unknown error";
+    }
+};
+
+boost::system::error_category const& my_category()
+{
+    static my_category_impl mycat;
+    return mycat;
+}
+
+int main()
+{
+    {
+        boost::system::error_code e1( 5, my_category() );
+        std::error_code e2( e1 );
+        boost::system::error_code e3( e2 );
+
+        BOOST_TEST_EQ( e1, e3 );
+        BOOST_TEST_EQ( e1.value(), e3.value() );
+        BOOST_TEST_EQ( &e1.category(), &e3.category() );
+    }
+
+    return boost::report_errors();
+}
+
+#endif

test/system_error_test3.cpp

@@ -1,4 +1,4 @@
-// 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
 
@@ -14,22 +14,36 @@ int main()
         sys::error_code ec( 5, sys::generic_category() );
         sys::system_error x1( ec );
 
-		BOOST_TEST_EQ( std::string( x1.what() ), ec.what() );
+        BOOST_TEST_EQ( std::string( x1.what() ), ec.what() );
     }
 
     {
-        BOOST_STATIC_CONSTEXPR boost::source_location loc = BOOST_CURRENT_LOCATION;
-
-        sys::error_code ec( 5, sys::system_category(), &loc );
+        sys::error_code ec( 5, sys::generic_category() );
         sys::system_error x1( ec, "prefix" );
 
         BOOST_TEST_EQ( std::string( x1.what() ), "prefix: " + ec.what() );
     }
 
     {
-        sys::system_error x1( 5, sys::generic_category() );
+        sys::error_code ec( 5, sys::generic_category() );
+        sys::system_error x1( ec, std::string( "prefix2" ) );
 
-        BOOST_TEST_EQ( std::string( x1.what() ), sys::error_code( 5, sys::generic_category() ).what() );
+        BOOST_TEST_EQ( std::string( x1.what() ), "prefix2: " + ec.what() );
+    }
+
+    {
+        BOOST_STATIC_CONSTEXPR boost::source_location loc = BOOST_CURRENT_LOCATION;
+
+        sys::error_code ec( 5, sys::generic_category(), &loc );
+        sys::system_error x1( ec, "prefix3" );
+
+        BOOST_TEST_EQ( std::string( x1.what() ), "prefix3: " + ec.what() );
+    }
+
+    {
+        sys::system_error x1( 5, sys::system_category() );
+
+        BOOST_TEST_EQ( std::string( x1.what() ), sys::error_code( 5, sys::system_category() ).what() );
     }
 
     {
@@ -38,5 +52,11 @@ int main()
         BOOST_TEST_EQ( std::string( x1.what() ), "prefix: " + sys::error_code( 5, sys::system_category() ).what() );
     }
 
+    {
+        sys::system_error x1( 5, sys::system_category(), std::string( "prefix2" ) );
+
+        BOOST_TEST_EQ( std::string( x1.what() ), "prefix2: " + sys::error_code( 5, sys::system_category() ).what() );
+    }
+
     return boost::report_errors();
 }