Add system/detail/mutex.hpp, use it in error_category_impl.hpp

.drone.jsonnet

@@ -173,48 +173,114 @@ local windows_pipeline(name, image, environment, arch = "amd64") =
     ),
 
     linux_pipeline(
-        "Linux 20.04 GCC 9 ARM64 32/64",
+        "Linux 20.04 GCC 9* ARM64",
         "cppalliance/droneubuntu2004:multiarch",
-        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a', ADDRMD: '32,64' },
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a' },
         arch="arm64",
     ),
 
     linux_pipeline(
-        "Linux 20.04 GCC 10 32 ASAN",
+        "Linux 20.04 GCC 9* S390x",
+        "cppalliance/droneubuntu2004:multiarch",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a' },
+        arch="s390x",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 10 32",
         "cppalliance/droneubuntu2004:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++-10', CXXSTD: '03,11,14,17,20', ADDRMD: '32' } + asan,
+        { TOOLSET: 'gcc', COMPILER: 'g++-10', CXXSTD: '03,11,14,17,20', ADDRMD: '32' },
         "g++-10-multilib",
     ),
 
     linux_pipeline(
-        "Linux 20.04 GCC 10 64 ASAN",
+        "Linux 20.04 GCC 10 64",
         "cppalliance/droneubuntu2004:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++-10', CXXSTD: '03,11,14,17,20', ADDRMD: '64' } + asan,
+        { TOOLSET: 'gcc', COMPILER: 'g++-10', CXXSTD: '03,11,14,17,20', ADDRMD: '64' },
         "g++-10-multilib",
     ),
 
     linux_pipeline(
-        "Linux 20.04 Clang 13",
-        "cppalliance/droneubuntu2004:1",
+        "Linux 22.04 GCC 11* 32",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a', ADDRMD: '32' },
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 11* 64",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14,17,2a', ADDRMD: '64' },
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 12 32 ASAN",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '03,11,14,17,20,2b', ADDRMD: '32' } + asan,
+        "g++-12-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 12 64 ASAN",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '03,11,14,17,20,2b', ADDRMD: '64' } + asan,
+        "g++-12-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 Clang 3.5",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.5', CXXSTD: '03,11' },
+        "clang-3.5",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 Clang 3.6",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.6', CXXSTD: '03,11,14' },
+        "clang-3.6",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 Clang 3.7",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.7', CXXSTD: '03,11,14' },
+        "clang-3.7",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 Clang 3.8",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.8', CXXSTD: '03,11,14' },
+        "clang-3.8",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 Clang 13",
+        "cppalliance/droneubuntu2204:1",
         { 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",
+        "Linux 22.04 Clang 14 UBSAN",
+        "cppalliance/droneubuntu2204:1",
         { 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",
+        "Linux 22.04 Clang 14 ASAN",
+        "cppalliance/droneubuntu2204:1",
         { 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"],
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 Clang 15",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-15', CXXSTD: '03,11,14,17,20,2b' },
+        "clang-15",
+        ["deb http://apt.llvm.org/jammy/ llvm-toolchain-jammy-15 main"],
     ),
 
     macos_pipeline(

.github/workflows/ci.yml

@@ -19,22 +19,26 @@ jobs:
         include:
           - toolset: gcc-4.8
             cxxstd: "03,11"
-            os: ubuntu-18.04
+            os: ubuntu-latest
+            container: ubuntu:18.04
             install: g++-4.8
           - toolset: gcc-5
             cxxstd: "03,11,14,1z"
-            os: ubuntu-18.04
+            os: ubuntu-latest
+            container: ubuntu:18.04
             install: g++-5
           - toolset: gcc-6
             cxxstd: "03,11,14,1z"
-            os: ubuntu-18.04
+            os: ubuntu-latest
+            container: ubuntu:18.04
             install: g++-6
           - toolset: gcc-7
             cxxstd: "03,11,14,17"
-            os: ubuntu-18.04
+            os: ubuntu-latest
+            container: ubuntu:18.04
           - toolset: gcc-8
             cxxstd: "03,11,14,17,2a"
-            os: ubuntu-18.04
+            os: ubuntu-20.04
             install: g++-8
           - toolset: gcc-9
             cxxstd: "03,11,14,17,2a"
@@ -48,33 +52,36 @@ jobs:
             os: ubuntu-20.04
             install: g++-11
           - toolset: gcc-12
-            cxxstd: "03,11,14,17,20"
+            cxxstd: "03,11,14,17,20,2b"
             os: ubuntu-22.04
             install: g++-12
           - toolset: clang
             compiler: clang++-3.9
             cxxstd: "03,11,14"
-            os: ubuntu-18.04
+            os: ubuntu-latest
+            container: ubuntu:18.04
             install: clang-3.9
           - toolset: clang
             compiler: clang++-4.0
             cxxstd: "03,11,14"
-            os: ubuntu-18.04
+            os: ubuntu-latest
+            container: ubuntu:18.04
             install: clang-4.0
           - toolset: clang
             compiler: clang++-5.0
             cxxstd: "03,11,14,1z"
-            os: ubuntu-18.04
+            os: ubuntu-latest
+            container: ubuntu:18.04
             install: clang-5.0
           - toolset: clang
             compiler: clang++-6.0
             cxxstd: "03,11,14,17"
-            os: ubuntu-18.04
+            os: ubuntu-20.04
             install: clang-6.0
           - toolset: clang
             compiler: clang++-7
             cxxstd: "03,11,14,17"
-            os: ubuntu-18.04
+            os: ubuntu-20.04
             install: clang-7
           - toolset: clang
             compiler: clang++-8
@@ -100,26 +107,40 @@ jobs:
             os: ubuntu-20.04
           - toolset: clang
             compiler: clang++-13
-            cxxstd: "03,11,14,17,20"
+            cxxstd: "03,11,14,17,20,2b"
             os: ubuntu-22.04
             install: clang-13
           - toolset: clang
             compiler: clang++-14
-            cxxstd: "03,11,14,17,20"
+            cxxstd: "03,11,14,17,20,2b"
             os: ubuntu-22.04
             install: clang-14
           - toolset: clang
             cxxstd: "03,11,14,17,2a"
-            os: macos-10.15
+            os: macos-11
+          - toolset: clang
+            cxxstd: "03,11,14,17,2a"
+            os: macos-12
 
     runs-on: ${{matrix.os}}
+    container: ${{matrix.container}}
+
+    defaults:
+      run:
+        shell: bash
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
+
+      - name: Setup container environment
+        if: matrix.container
+        run: |
+          apt-get update
+          apt-get -y install sudo python git g++
 
       - name: Install packages
         if: matrix.install
-        run: sudo apt install ${{matrix.install}}
+        run: sudo apt-get -y install ${{matrix.install}}
 
       - name: Setup Boost
         run: |
@@ -182,7 +203,7 @@ jobs:
     runs-on: ${{matrix.os}}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Setup Boost
         shell: cmd
@@ -217,19 +238,19 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: ubuntu-18.04
           - os: ubuntu-20.04
           - os: ubuntu-22.04
-          - os: macos-10.15
+          - os: macos-11
+          - os: macos-12
 
     runs-on: ${{matrix.os}}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Install packages
         if: matrix.install
-        run: sudo apt install ${{matrix.install}}
+        run: sudo apt-get -y install ${{matrix.install}}
 
       - name: Setup Boost
         run: |
@@ -264,19 +285,19 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: ubuntu-18.04
           - os: ubuntu-20.04
           - os: ubuntu-22.04
-          - os: macos-10.15
+          - os: macos-11
+          - os: macos-12
 
     runs-on: ${{matrix.os}}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Install packages
         if: matrix.install
-        run: sudo apt install ${{matrix.install}}
+        run: sudo apt-get -y install ${{matrix.install}}
 
       - name: Setup Boost
         run: |
@@ -321,19 +342,19 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: ubuntu-18.04
           - os: ubuntu-20.04
           - os: ubuntu-22.04
-          - os: macos-10.15
+          - os: macos-11
+          - os: macos-12
 
     runs-on: ${{matrix.os}}
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v3
 
       - name: Install packages
         if: matrix.install
-        run: sudo apt install ${{matrix.install}}
+        run: sudo apt-get -y install ${{matrix.install}}
 
       - name: Setup Boost
         run: |

CMakeLists.txt

@@ -2,7 +2,7 @@
 # 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
 
-cmake_minimum_required(VERSION 3.5...3.16)
+cmake_minimum_required(VERSION 3.5...3.20)
 
 project(boost_system VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CXX)
 
@@ -20,6 +20,15 @@ target_link_libraries(boost_system
     Boost::winapi
 )
 
+if(CMAKE_VERSION VERSION_GREATER 3.18 AND CMAKE_GENERATOR MATCHES "Visual Studio")
+
+  file(GLOB_RECURSE boost_system_IDEFILES CONFIGURE_DEPENDS include/*.hpp)
+  source_group(TREE ${PROJECT_SOURCE_DIR}/include FILES ${boost_system_IDEFILES} PREFIX "Header Files")
+  list(APPEND boost_system_IDEFILES extra/boost_system.natvis)
+  target_sources(boost_system PRIVATE ${boost_system_IDEFILES})
+
+endif()
+
 if(BUILD_TESTING)
 
   add_subdirectory(test)

appveyor.yml

@@ -40,6 +40,12 @@ environment:
       ADDPATH: C:\mingw-w64\x86_64-6.3.0-posix-seh-rt_v5-rev1\mingw64\bin;
       TOOLSET: gcc
       CXXSTD: 03,11,14,1z
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2015
+      CMAKE: 1
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      CMAKE_SUBDIR: 1
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
+      CMAKE_INSTALL: 1
 
 install:
   - set BOOST_BRANCH=develop
@@ -59,4 +65,27 @@ test_script:
   - PATH=%ADDPATH%%PATH%
   - if not "%CXXSTD%" == "" set CXXSTD=cxxstd=%CXXSTD%
   - if not "%ADDRMD%" == "" set ADDRMD=address-model=%ADDRMD%
-  - b2 -j3 libs/system/test toolset=%TOOLSET% %CXXSTD% %ADDRMD% variant=debug,release embed-manifest-via=linker
+  - if "%CMAKE%%CMAKE_SUBDIR%%CMAKE_INSTALL%" == ""  b2 -j3 libs/system/test toolset=%TOOLSET% %CXXSTD% %ADDRMD% variant=debug,release embed-manifest-via=linker
+
+  - if not "%CMAKE%" == ""  mkdir __build__ && cd __build__
+  - if not "%CMAKE%" == ""  cmake -DBUILD_TESTING=ON -DBOOST_INCLUDE_LIBRARIES=system -DBoost_VERBOSE=ON ..
+  - if not "%CMAKE%" == ""  cmake --build . --target tests -j 3 --config Debug & ctest --output-on-failure --no-tests=error -j 3 -C Debug
+  - if not "%CMAKE%" == ""  cmake --build . --target tests -j 3 --config Release & ctest --output-on-failure --no-tests=error -j 3 -C Release
+  - if not "%CMAKE%" == ""  cmake --build . --target tests -j 3 --config MinSizeRel & ctest --output-on-failure --no-tests=error -j 3 -C MinSizeRel
+  - if not "%CMAKE%" == ""  cmake --build . --target tests -j 3 --config RelWithDebInfo & ctest --output-on-failure --no-tests=error -j 3 -C RelWithDebInfo
+
+  - if not "%CMAKE_SUBDIR%" == ""  cd libs/system/test/cmake_subdir_test && mkdir __build__ && cd __build__
+  - if not "%CMAKE_SUBDIR%" == ""  cmake ..
+  - if not "%CMAKE_SUBDIR%" == ""  cmake --build . --config Debug && cmake --build . --target check --config Debug
+  - if not "%CMAKE_SUBDIR%" == ""  cmake --build . --config Release && cmake --build . --target check --config Release
+  - if not "%CMAKE_SUBDIR%" == ""  cmake --build . --config MinSizeRel && cmake --build . --target check --config MinSizeRel
+  - if not "%CMAKE_SUBDIR%" == ""  cmake --build . --config RelWithDebInfo && cmake --build . --target check --config RelWithDebInfo
+
+  - if not "%CMAKE_INSTALL%" == ""  mkdir __build__ && cd __build__
+  - if not "%CMAKE_INSTALL%" == ""  cmake -DBOOST_INCLUDE_LIBRARIES=system -DCMAKE_INSTALL_PREFIX=C:/cmake-prefix ..
+  - if not "%CMAKE_INSTALL%" == ""  cmake --build . --target install --config Debug
+  - if not "%CMAKE_INSTALL%" == ""  cmake --build . --target install --config Release
+  - if not "%CMAKE_INSTALL%" == ""  cd ../libs/system/test/cmake_install_test && mkdir __build__ && cd __build__
+  - if not "%CMAKE_INSTALL%" == ""  cmake -DCMAKE_INSTALL_PREFIX=C:/cmake-prefix ..
+  - if not "%CMAKE_INSTALL%" == ""  cmake --build . --config Debug && cmake --build . --target check --config Debug
+  - if not "%CMAKE_INSTALL%" == ""  cmake --build . --config Release && cmake --build . --target check --config Release

doc/system/changes.adoc

@@ -8,6 +8,14 @@ https://www.boost.org/LICENSE_1_0.txt
 # Revision History
 :idprefix:
 
+## Changes in Boost 1.81
+
+* The macro `BOOST_SYSTEM_DISABLE_THREADS` can now be defined to disable
+  the use of `<mutex>` (e.g. on single-threaded libstdc++).
+* Added `value_type`, `error_type`, `in_place_value`, `in_place_error`
+  to `result<>`.
+* Added `emplace` to `result<>`.
+
 ## Changes in Boost 1.80
 
 * When an `error_code` is converted to `std::error_code` and then back

doc/system/reference.adoc

@@ -29,6 +29,11 @@ When `BOOST_SYSTEM_USE_UTF8` is defined, on Windows the library returns
 UTF-8 messages using code page `CP_UTF8` instead of the default `CP_ACP`.
 This macro has no effect on POSIX.
 
+When `BOOST_SYSTEM_DISABLE_THREADS` is defined, the library assumes that
+the current platform doesn't support multiple threads and disables the use
+of the standard header `<mutex>`, eliminating the mutex locks. The single
+threaded `libstdc++` is one such platform.
+
 ## Deprecated Names
 
 In the process of adding Boost.System to the {cpp}11 standard library, the
@@ -1595,6 +1600,12 @@ template<class T, class E = error_code> class result
 {
 public:
 
+    using value_type = T;
+    using error_type = E;
+
+    static constexpr in_place_value_t in_place_value{};
+    static constexpr in_place_error_t in_place_error{};
+
     // constructors
 
     constexpr result();
@@ -1648,6 +1659,11 @@ public:
 
     constexpr E error() const;
 
+    // emplace
+
+    template<class... A>
+      constexpr T& emplace( A&&... a );
+
     // swap
 
     constexpr void swap( result& r );
@@ -1843,6 +1859,20 @@ constexpr E error() const;
 Effects: ::
   If `*this` holds an error, returns it. Otherwise, returns `E()`.
 
+#### emplace
+
+```
+template<class... A>
+  constexpr T& emplace( A&&... a );
+```
+[none]
+* {blank}
++
+Ensures: ::
+  `*this` holds the value `T( std::forward<A>(a)... )`.
+Returns: ::
+  A reference to the contained value.
+
 #### swap
 
 ```
@@ -1911,6 +1941,12 @@ template<class E> class result<void, E>
 {
 public:
 
+    using value_type = void;
+    using error_type = E;
+
+    static constexpr in_place_value_t in_place_value{};
+    static constexpr in_place_error_t in_place_error{};
+
     // constructors
 
     constexpr result() noexcept;
@@ -1945,6 +1981,10 @@ public:
 
     constexpr E error() const;
 
+    // emplace
+
+    constexpr void emplace();
+
     // swap
 
     constexpr void swap( result& r );
@@ -2088,6 +2128,17 @@ constexpr E error() const;
 Effects: ::
   If `*this` holds an error, returns it. Otherwise, returns `E()`.
 
+#### emplace
+
+```
+constexpr void emplace();
+```
+[none]
+* {blank}
++
+Ensures: ::
+  `*this` holds an unspecified value.
+
 #### swap
 
 ```

extra/boost_system.natvis

@@ -0,0 +1,53 @@
+<?xml version="1.0" encoding="utf-8"?>
+<AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
+
+    <Type Name="boost::system::error_category">
+        <DisplayString Condition="id_ == 0xb2ab117a257edfd0">[generic]</DisplayString>
+        <DisplayString Condition="id_ == 0xb2ab117a257edfd1">[system]</DisplayString>
+        <DisplayString Condition="id_ == 0xb2ab117a257edfd2">[interop]</DisplayString>
+        <DisplayString Condition="id_ != 0">[{id_,x}]</DisplayString>
+        <DisplayString>@{((uintptr_t)this),x}</DisplayString>
+    </Type>
+
+    <Type Name="boost::system::error_code">
+        <DisplayString Condition="lc_flags_ == 0">{d1_.val_} [system] ✓</DisplayString>
+
+        <DisplayString Condition="lc_flags_ == 1 &amp;&amp; ((std::error_code*)d2_)->_Mycat->_Addr==1">{((std::error_code*)d2_)->_Myval} [std:future]</DisplayString>
+        <DisplayString Condition="lc_flags_ == 1 &amp;&amp; ((std::error_code*)d2_)->_Mycat->_Addr==3">{((std::error_code*)d2_)->_Myval} [std:generic]</DisplayString>
+        <DisplayString Condition="lc_flags_ == 1 &amp;&amp; ((std::error_code*)d2_)->_Mycat->_Addr==5">{((std::error_code*)d2_)->_Myval} [std:iostream]</DisplayString>
+        <DisplayString Condition="lc_flags_ == 1 &amp;&amp; ((std::error_code*)d2_)->_Mycat->_Addr==7">{((std::error_code*)d2_)->_Myval} [std:system]</DisplayString>
+        <DisplayString Condition="lc_flags_ == 1">{((std::error_code*)d2_)->_Myval} std@{((uintptr_t)((std::error_code*)d2_)->_Mycat),x}</DisplayString>
+
+        <DisplayString Condition="d1_.cat_->id_ == 0xb2ab117a257edfd0 &amp;&amp;
+            (lc_flags_ == 2 || (lc_flags_ &gt; 3 &amp;&amp; ( lc_flags_ % 2 == 0 )))">{d1_.val_} [generic] ✓</DisplayString>
+        <DisplayString Condition="d1_.cat_->id_ == 0xb2ab117a257edfd1 &amp;&amp;
+            (lc_flags_ == 2 || (lc_flags_ &gt; 3 &amp;&amp; ( lc_flags_ % 2 == 0 )))">{d1_.val_} [system] ✓</DisplayString>
+        <DisplayString Condition="d1_.cat_->id_ == 0xb2ab117a257edfd2 &amp;&amp;
+            (lc_flags_ == 2 || (lc_flags_ &gt; 3 &amp;&amp; ( lc_flags_ % 2 == 0 )))">{d1_.val_} [interop] ✓</DisplayString>
+        <DisplayString Condition="d1_.cat_->id_ != 0 &amp;&amp;
+            (lc_flags_ == 2 || (lc_flags_ &gt; 3 &amp;&amp; ( lc_flags_ % 2 == 0 )))">{d1_.val_} [{d1_.cat_->id_,x}] ✓</DisplayString>
+        <DisplayString Condition=
+            "lc_flags_ == 2 || (lc_flags_ &gt; 3 &amp;&amp; ( lc_flags_ % 2 == 0 ))">{d1_.val_} @{((uintptr_t)d1_.cat_),x} ✓</DisplayString>
+
+        <DisplayString Condition="d1_.cat_->id_ == 0xb2ab117a257edfd0 &amp;&amp;
+            (lc_flags_ &gt;= 3 &amp;&amp; ( lc_flags_ % 2 == 1 ))">{d1_.val_} [generic]</DisplayString>
+        <DisplayString Condition="d1_.cat_->id_ == 0xb2ab117a257edfd1 &amp;&amp;
+            (lc_flags_ &gt;= 3 &amp;&amp; ( lc_flags_ % 2 == 1 ))">{d1_.val_} [system]</DisplayString>
+        <DisplayString Condition="d1_.cat_->id_ == 0xb2ab117a257edfd2 &amp;&amp;
+            (lc_flags_ &gt;= 3 &amp;&amp; ( lc_flags_ % 2 == 1 ))">{d1_.val_} [interop]</DisplayString>
+        <DisplayString Condition="d1_.cat_->id_ != 0 &amp;&amp;
+            (lc_flags_ &gt;= 3 &amp;&amp; ( lc_flags_ % 2 == 1 ))">{d1_.val_} [{d1_.cat_->id_,x}]</DisplayString>
+        <DisplayString Condition=
+            "lc_flags_ &gt;= 3 &amp;&amp; ( lc_flags_ % 2 == 1 )">{d1_.val_} @{((uintptr_t)d1_.cat_),x}</DisplayString>
+
+        <Expand>
+            <Item Name="std::error_code" Condition="lc_flags_ == 1">(std::error_code*)d2_</Item>
+            <Item Name="[location]" Condition="lc_flags_ &gt; 3">*((boost::source_location*)(lc_flags_ &amp; ~1))</Item>
+        </Expand>
+    </Type>
+
+    <Type Name="boost::system::result&lt;*,*&gt;">
+        <DisplayString>{v_}</DisplayString>
+    </Type>
+
+</AutoVisualizer>

include/boost/system/detail/config.hpp

@@ -12,8 +12,14 @@
 #include <boost/config/workaround.hpp>
 
 // BOOST_SYSTEM_HAS_SYSTEM_ERROR
+//
+// The macro BOOST_SYSTEM_DISABLE_THREADS can be defined on configurations
+// that provide <system_error> and <atomic>, but not <mutex>, such as the
+// single-threaded libstdc++.
+//
+// https://github.com/boostorg/system/issues/92
 
-#if !defined(BOOST_NO_CXX11_HDR_SYSTEM_ERROR) && !defined(BOOST_NO_CXX11_HDR_ATOMIC) && !defined(BOOST_NO_CXX11_HDR_MUTEX)
+#if !defined(BOOST_NO_CXX11_HDR_SYSTEM_ERROR) && !defined(BOOST_NO_CXX11_HDR_ATOMIC) && ( !defined(BOOST_NO_CXX11_HDR_MUTEX) || defined(BOOST_SYSTEM_DISABLE_THREADS) )
 # define BOOST_SYSTEM_HAS_SYSTEM_ERROR
 #endif
 
@@ -58,7 +64,9 @@
 
 // BOOST_SYSTEM_CLANG_6
 
-#if defined(__clang__) && (__clang_major__ < 7 || (defined(__APPLE__) && __clang_major__ < 11))
+// Android NDK r18b has Clang 7.0.2 that still needs the workaround
+// https://github.com/boostorg/system/issues/100
+#if defined(__clang__) && (__clang_major__ < 7 || (defined(__APPLE__) && __clang_major__ < 11) || (defined(__ANDROID__) && __clang_major__ == 7))
 # define BOOST_SYSTEM_CLANG_6
 #endif
 

include/boost/system/detail/error_category.hpp

@@ -48,7 +48,7 @@ class std_category;
 #pragma GCC diagnostic ignored "-Wnon-virtual-dtor"
 #endif
 
-#if defined(BOOST_MSVC)
+#if defined(BOOST_MSVC) && BOOST_MSVC < 1900
 #pragma warning(push)
 #pragma warning(disable: 4351) //  new behavior: elements of array will be default initialized
 #endif
@@ -183,7 +183,7 @@ public:
 #endif
 };
 
-#if defined(BOOST_MSVC)
+#if defined(BOOST_MSVC) && BOOST_MSVC < 1900
 #pragma warning(pop)
 #endif
 

include/boost/system/detail/error_category_impl.hpp

@@ -98,7 +98,7 @@ 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_impl.hpp>
-#include <mutex>
+#include <boost/system/detail/mutex.hpp>
 #include <new>
 
 namespace boost
@@ -111,10 +111,10 @@ namespace detail
 
 template<class = void> struct stdcat_mx_holder
 {
-    static std::mutex mx_;
+    static mutex mx_;
 };
 
-template<class T> std::mutex stdcat_mx_holder<T>::mx_;
+template<class T> mutex stdcat_mx_holder<T>::mx_;
 
 } // namespace detail
 
@@ -130,11 +130,11 @@ inline void error_category::init_stdcat() const
 
 #endif
 
-    std::lock_guard<std::mutex> lk( boost::system::detail::stdcat_mx_holder<>::mx_ );
+    system::detail::lock_guard<system::detail::mutex> lk( 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 );
+        ::new( static_cast<void*>( stdcat_ ) ) boost::system::detail::std_category( this, system::detail::id_wrapper<0>() );
         sc_init_.store( 1, std::memory_order_release );
     }
 }
@@ -151,7 +151,7 @@ inline BOOST_NOINLINE error_category::operator std::error_category const & () co
 // 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 );
+        static const boost::system::detail::std_category generic_instance( this, system::detail::id_wrapper<0x1F4D3>() );
         return generic_instance;
 
 #else
@@ -166,7 +166,7 @@ inline BOOST_NOINLINE error_category::operator std::error_category const & () co
 // 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 );
+        static const boost::system::detail::std_category system_instance( this, system::detail::id_wrapper<0x1F4D7>() );
         return system_instance;
 
 #else

include/boost/system/detail/error_code.hpp

@@ -29,6 +29,7 @@
 #include <boost/assert/source_location.hpp>
 #include <boost/cstdint.hpp>
 #include <boost/config.hpp>
+#include <boost/config/workaround.hpp>
 #include <ostream>
 #include <new>
 #include <cstdio>
@@ -57,12 +58,14 @@ namespace system
 //  and error_code containing a pointer to an object of a type derived
 //  from error_category.
 
+bool operator==( const error_code & code, const error_condition & condition ) BOOST_NOEXCEPT;
 std::size_t hash_value( error_code const & ec );
 
 class error_code
 {
 private:
 
+    friend bool operator==( const error_code & code, const error_condition & condition ) BOOST_NOEXCEPT;
     friend std::size_t hash_value( error_code const & ec );
 
 private:
@@ -114,7 +117,10 @@ public:
 
     // constructors:
 
-    BOOST_SYSTEM_CONSTEXPR error_code() BOOST_NOEXCEPT:
+#if !BOOST_WORKAROUND(BOOST_GCC, < 40800)
+    BOOST_CONSTEXPR
+#endif
+    error_code() BOOST_NOEXCEPT:
         d1_(), lc_flags_( 0 )
     {
     }
@@ -397,7 +403,12 @@ public:
     {
 #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
 
-        if( lhs.lc_flags_ == 1 && rhs.lc_flags_ == 1 )
+        bool s1 = lhs.lc_flags_ == 1;
+        bool s2 = rhs.lc_flags_ == 1;
+
+        if( s1 != s2 ) return false;
+
+        if( s1 && s2 )
         {
             std::error_code const& e1 = *reinterpret_cast<std::error_code const*>( lhs.d2_ );
             std::error_code const& e2 = *reinterpret_cast<std::error_code const*>( rhs.d2_ );
@@ -415,7 +426,13 @@ public:
     {
 #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
 
-        if( lhs.lc_flags_ == 1 && rhs.lc_flags_ == 1 )
+        bool s1 = lhs.lc_flags_ == 1;
+        bool s2 = rhs.lc_flags_ == 1;
+
+        if( s1 < s2 ) return true;
+        if( s2 < s1 ) return false;
+
+        if( s1 && s2 )
         {
             std::error_code const& e1 = *reinterpret_cast<std::error_code const*>( lhs.d2_ );
             std::error_code const& e2 = *reinterpret_cast<std::error_code const*>( rhs.d2_ );
@@ -434,48 +451,6 @@ public:
         return !( lhs == rhs );
     }
 
-    inline friend bool operator==( const error_code & code, const error_condition & condition ) BOOST_NOEXCEPT
-    {
-#if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
-
-        if( code.lc_flags_ == 1 )
-        {
-            return static_cast<std::error_code>( code ) == static_cast<std::error_condition>( condition );
-        }
-        else
-
-#endif
-        {
-            return code.category().equivalent( code.value(), condition ) || condition.category().equivalent( code, condition.value() );
-        }
-    }
-
-    inline friend bool operator==( const error_condition & condition, const error_code & code ) BOOST_NOEXCEPT
-    {
-#if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
-
-        if( code.lc_flags_ == 1 )
-        {
-            return static_cast<std::error_code>( code ) == static_cast<std::error_condition>( condition );
-        }
-        else
-
-#endif
-        {
-            return code.category().equivalent( code.value(), condition ) || condition.category().equivalent( code, condition.value() );
-        }
-    }
-
-    inline friend bool operator!=( const error_code & lhs, const error_condition & rhs ) BOOST_NOEXCEPT
-    {
-        return !( lhs == rhs );
-    }
-
-    inline friend bool operator!=( const error_condition & lhs, const error_code & rhs ) BOOST_NOEXCEPT
-    {
-        return !( lhs == rhs );
-    }
-
 #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
 
     inline friend bool operator==( std::error_code const & lhs, error_code const & rhs ) BOOST_NOEXCEPT
@@ -678,6 +653,37 @@ public:
     }
 };
 
+inline bool operator==( const error_code & code, const error_condition & condition ) BOOST_NOEXCEPT
+{
+#if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
+
+    if( code.lc_flags_ == 1 )
+    {
+        return static_cast<std::error_code>( code ) == static_cast<std::error_condition>( condition );
+    }
+    else
+
+#endif
+    {
+        return code.category().equivalent( code.value(), condition ) || condition.category().equivalent( code, condition.value() );
+    }
+}
+
+inline bool operator==( const error_condition & condition, const error_code & code ) BOOST_NOEXCEPT
+{
+    return code == condition;
+}
+
+inline bool operator!=( const error_code & lhs, const error_condition & rhs ) BOOST_NOEXCEPT
+{
+    return !( lhs == rhs );
+}
+
+inline bool operator!=( const error_condition & lhs, const error_code & rhs ) BOOST_NOEXCEPT
+{
+    return !( lhs == rhs );
+}
+
 inline std::size_t hash_value( error_code const & ec )
 {
 #if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)

include/boost/system/detail/error_condition.hpp

@@ -261,6 +261,58 @@ public:
         return !( lhs == rhs );
     }
 
+    //
+
+    template<class E, class N = typename detail::enable_if<std::is_error_condition_enum<E>::value>::type>
+    BOOST_SYSTEM_CONSTEXPR inline friend bool operator==( error_condition const & lhs, E rhs ) BOOST_NOEXCEPT
+    {
+        return lhs == make_error_condition( rhs );
+    }
+
+    template<class E, class N = typename detail::enable_if<std::is_error_condition_enum<E>::value>::type>
+    BOOST_SYSTEM_CONSTEXPR inline friend bool operator==( E lhs, error_condition const & rhs ) BOOST_NOEXCEPT
+    {
+        return make_error_condition( lhs ) == rhs;
+    }
+
+    template<class E, class N = typename detail::enable_if<std::is_error_condition_enum<E>::value>::type>
+    BOOST_SYSTEM_CONSTEXPR inline friend bool operator!=( error_condition const & lhs, E rhs ) BOOST_NOEXCEPT
+    {
+        return !( lhs == rhs );
+    }
+
+    template<class E, class N = typename detail::enable_if<std::is_error_condition_enum<E>::value>::type>
+    BOOST_SYSTEM_CONSTEXPR inline friend bool operator!=( E lhs, error_condition const & rhs ) BOOST_NOEXCEPT
+    {
+        return !( lhs == rhs );
+    }
+
+    //
+
+    template<class E, class N1 = void, class N2 = typename detail::enable_if<std::is_error_code_enum<E>::value>::type>
+    inline friend bool operator==( error_condition const & lhs, E rhs ) BOOST_NOEXCEPT
+    {
+        return lhs == make_error_code( rhs );
+    }
+
+    template<class E, class N1 = void, class N2 = typename detail::enable_if<std::is_error_code_enum<E>::value>::type>
+    inline friend bool operator==( E lhs, error_condition const & rhs ) BOOST_NOEXCEPT
+    {
+        return make_error_code( lhs ) == rhs;
+    }
+
+    template<class E, class N1 = void, class N2 = typename detail::enable_if<std::is_error_code_enum<E>::value>::type>
+    inline friend bool operator!=( error_condition const & lhs, E rhs ) BOOST_NOEXCEPT
+    {
+        return !( lhs == rhs );
+    }
+
+    template<class E, class N1 = void, class N2 = typename detail::enable_if<std::is_error_code_enum<E>::value>::type>
+    inline friend bool operator!=( E lhs, error_condition const & rhs ) BOOST_NOEXCEPT
+    {
+        return !( lhs == rhs );
+    }
+
 #endif
 
     std::string to_string() const

include/boost/system/detail/mutex.hpp

@@ -0,0 +1,88 @@
+#ifndef BOOST_SYSTEM_DETAIL_MUTEX_HPP_INCLUDED
+#define BOOST_SYSTEM_DETAIL_MUTEX_HPP_INCLUDED
+
+// Copyright 2023 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt)
+
+#include <boost/config.hpp>
+
+#if defined(BOOST_SYSTEM_DISABLE_THREADS)
+
+namespace boost
+{
+namespace system
+{
+namespace detail
+{
+
+struct mutex
+{
+    void lock()
+    {
+    }
+
+    void unlock()
+    {
+    }
+};
+
+} // namespace detail
+} // namespace system
+} // namespace boost
+
+#else
+
+#include <mutex>
+
+namespace boost
+{
+namespace system
+{
+namespace detail
+{
+
+using std::mutex;
+
+} // namespace detail
+} // namespace system
+} // namespace boost
+
+#endif
+
+namespace boost
+{
+namespace system
+{
+namespace detail
+{
+
+template<class Mtx> class lock_guard
+{
+private:
+
+    Mtx& mtx_;
+
+private:
+
+    lock_guard( lock_guard const& );
+    lock_guard& operator=( lock_guard const& );
+
+public:
+
+    explicit lock_guard( Mtx& mtx ): mtx_( mtx )
+    {
+        mtx_.lock();
+    }
+
+    ~lock_guard()
+    {
+        mtx_.unlock();
+    }
+};
+
+} // namespace detail
+} // namespace system
+} // namespace boost
+
+#endif // #ifndef BOOST_SYSTEM_DETAIL_MUTEX_HPP_INCLUDED

include/boost/system/detail/std_category.hpp

@@ -11,6 +11,7 @@
 // See library home page at http://www.boost.org/libs/system
 
 #include <boost/system/detail/error_category.hpp>
+#include <boost/config.hpp>
 #include <system_error>
 
 //
@@ -24,6 +25,8 @@ namespace system
 namespace detail
 {
 
+template<unsigned Id> struct id_wrapper {};
+
 class BOOST_SYMBOL_VISIBLE std_category: public std::error_category
 {
 private:
@@ -39,20 +42,22 @@ public:
 
 public:
 
-    explicit std_category( boost::system::error_category const * pc, unsigned id ): pc_( pc )
+    template<unsigned Id>
+    explicit std_category( boost::system::error_category const * pc, id_wrapper<Id> ): pc_( pc )
     {
-        if( id != 0 )
-        {
 #if defined(_MSC_VER) && defined(_CPPLIB_VER) && _MSC_VER >= 1900 && _MSC_VER < 2000
 
-            // Poking into the protected _Addr member of std::error_category
-            // is not a particularly good programming practice, but what can
-            // you do
+        // We used to assign to the protected _Addr member of std::error_category
+        // here when Id != 0, but this should never happen now because this code
+        // path is no longer used
 
-            _Addr = id;
+#if !defined(BOOST_NO_CXX11_STATIC_ASSERT)
+
+        static_assert( Id == 0, "This constructor should only be called with Id == 0 under MS STL 14.0+" );
+
+#endif
 
 #endif
-        }
     }
 
     const char * name() const BOOST_NOEXCEPT BOOST_OVERRIDE

include/boost/system/detail/system_category_condition_win32.hpp

@@ -59,6 +59,7 @@ inline int system_category_condition_win32( int ev ) BOOST_NOEXCEPT
     case ERROR_ACCESS_DENIED_: return permission_denied;
     case ERROR_ALREADY_EXISTS_: return file_exists;
     case ERROR_BAD_NETPATH_: return no_such_file_or_directory;
+    case ERROR_BAD_NET_NAME_: return no_such_file_or_directory;
     case ERROR_BAD_UNIT_: return no_such_device;
     case ERROR_BROKEN_PIPE_: return broken_pipe;
     case ERROR_BUFFER_OVERFLOW_: return filename_too_long;
@@ -75,6 +76,7 @@ inline int system_category_condition_win32( int ev ) BOOST_NOEXCEPT
     case ERROR_DIR_NOT_EMPTY_: return directory_not_empty;
     case ERROR_DIRECTORY_: return invalid_argument; // WinError.h: "The directory name is invalid"
     case ERROR_DISK_FULL_: return no_space_on_device;
+    case ERROR_FILENAME_EXCED_RANGE_: return filename_too_long;
     case ERROR_FILE_EXISTS_: return file_exists;
     case ERROR_FILE_NOT_FOUND_: return no_such_file_or_directory;
     case ERROR_HANDLE_DISK_FULL_: return no_space_on_device;
@@ -100,12 +102,16 @@ inline int system_category_condition_win32( int ev ) BOOST_NOEXCEPT
     case ERROR_REPARSE_TAG_INVALID_: return invalid_argument;
     case ERROR_RETRY_: return resource_unavailable_try_again;
     case ERROR_SEEK_: return io_error;
+    case ERROR_SEM_TIMEOUT_: return timed_out;
     case ERROR_SHARING_VIOLATION_: return permission_denied;
     case ERROR_NOT_SUPPORTED_: return not_supported; // WinError.h: "The request is not supported."
+    case ERROR_TIMEOUT_: return timed_out;
     case ERROR_TOO_MANY_OPEN_FILES_: return too_many_files_open;
     case ERROR_WRITE_FAULT_: return io_error;
     case ERROR_WRITE_PROTECT_: return permission_denied;
 
+    case 258: return timed_out; // WAIT_TIMEOUT
+
     case WSAEACCES_: return permission_denied;
     case WSAEADDRINUSE_: return address_in_use;
     case WSAEADDRNOTAVAIL_: return address_not_available;

include/boost/system/result.hpp

@@ -95,6 +95,14 @@ private:
 
     variant2::variant<T, E> v_;
 
+public:
+
+    using value_type = T;
+    using error_type = E;
+
+    static constexpr in_place_value_t in_place_value{};
+    static constexpr in_place_error_t in_place_error{};
+
 public:
 
     // constructors
@@ -135,7 +143,8 @@ public:
     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
+        !std::is_constructible<E, A...>::value &&
+        sizeof...(A) >= 1
         >::type>
     explicit constexpr result( A&&... a )
         noexcept( std::is_nothrow_constructible<T, A...>::value )
@@ -146,7 +155,8 @@ public:
     // explicit, error
     template<class... A, class En2 = void, class En = typename std::enable_if<
         !std::is_constructible<T, A...>::value &&
-        std::is_constructible<E, A...>::value
+        std::is_constructible<E, A...>::value &&
+        sizeof...(A) >= 1
         >::type>
     explicit constexpr result( A&&... a )
         noexcept( std::is_nothrow_constructible<E, A...>::value )
@@ -220,7 +230,7 @@ public:
 
     constexpr bool has_error() const noexcept
     {
-        return v_.index() != 0;
+        return v_.index() == 1;
     }
 
     constexpr explicit operator bool() const noexcept
@@ -391,6 +401,14 @@ public:
         return has_error()? variant2::unsafe_get<1>( v_ ): E();
     }
 
+    // emplace
+
+    template<class... A>
+    BOOST_CXX14_CONSTEXPR T& emplace( A&&... a )
+    {
+        return v_.template emplace<0>( std::forward<A>(a)... );
+    }
+
     // swap
 
     BOOST_CXX14_CONSTEXPR void swap( result& r )
@@ -442,6 +460,14 @@ private:
 
     variant2::variant<variant2::monostate, E> v_;
 
+public:
+
+    using value_type = void;
+    using error_type = E;
+
+    static constexpr in_place_value_t in_place_value{};
+    static constexpr in_place_error_t in_place_error{};
+
 public:
 
     // constructors
@@ -509,7 +535,7 @@ public:
 
     constexpr bool has_error() const noexcept
     {
-        return v_.index() != 0;
+        return v_.index() == 1;
     }
 
     constexpr explicit operator bool() const noexcept
@@ -555,6 +581,13 @@ public:
         return has_error()? variant2::unsafe_get<1>( v_ ): E();
     }
 
+    // emplace
+
+    BOOST_CXX14_CONSTEXPR void emplace()
+    {
+        v_.template emplace<0>();
+    }
+
     // swap
 
     BOOST_CXX14_CONSTEXPR void swap( result& r )

test/CMakeLists.txt

@@ -15,6 +15,7 @@ macro(system_run s1)
   boost_test(SOURCES ${s1} ${ARGN})
   boost_test(SOURCES ${s1} ${ARGN} COMPILE_DEFINITIONS BOOST_NO_ANSI_APIS NAME ${n1}_no_ansi)
   boost_test(SOURCES ${s1} ${ARGN} COMPILE_DEFINITIONS BOOST_SYSTEM_USE_UTF8 NAME ${n1}_utf8)
+  boost_test(SOURCES ${s1} ${ARGN} COMPILE_DEFINITIONS BOOST_SYSTEM_DISABLE_THREADS NAME ${n1}_nthr)
 
 endmacro()
 
@@ -124,6 +125,15 @@ 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)
 
+boost_test(TYPE compile SOURCES constexpr_test2.cpp)
+
+boost_test(TYPE run SOURCES error_code_test3.cpp)
+boost_test(TYPE run SOURCES std_interop_test15.cpp)
+
+boost_test(TYPE run SOURCES win32_generic_test.cpp)
+
+boost_test(TYPE run SOURCES ec_hash_value_test.cpp)
+
 # result
 
 set(BOOST_TEST_COMPILE_FEATURES cxx_std_11)
@@ -143,3 +153,6 @@ 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)
+boost_test(TYPE run SOURCES result_typedefs.cpp)
+boost_test(TYPE run SOURCES result_value_construct3.cpp)
+boost_test(TYPE run SOURCES result_error_construct3.cpp)

test/Jamfile.v2

@@ -33,6 +33,7 @@ rule system-run ( sources + )
     result += [ run $(sources) : : : <library>/boost/system//boost_system <link>shared : $(sources[1]:B)_shared ] ;
     result += [ run $(sources) : : : <define>BOOST_NO_ANSI_APIS : $(sources[1]:B)_no_ansi ] ;
     result += [ run $(sources) : : : <define>BOOST_SYSTEM_USE_UTF8 : $(sources[1]:B)_utf8 ] ;
+    result += [ run $(sources) : : : <define>BOOST_SYSTEM_DISABLE_THREADS : $(sources[1]:B)_nthr ] ;
 
     return $(result) ;
 }
@@ -152,6 +153,15 @@ run std_interop_test14.cpp ;
 run ec_location_test3.cpp ;
 run ec_location_test4.cpp ;
 
+compile constexpr_test2.cpp ;
+
+run error_code_test3.cpp ;
+run std_interop_test15.cpp ;
+
+run win32_generic_test.cpp ;
+
+run ec_hash_value_test.cpp ;
+
 # result
 
 import ../../config/checks/config : requires ;
@@ -174,3 +184,7 @@ run result_value_construct2.cpp : : : $(CPP11) ;
 run result_error_construct2.cpp : : : $(CPP11) ;
 run result_errc_construct.cpp : : : $(CPP11) ;
 run result_convert_construct.cpp : : : $(CPP11) ;
+run result_typedefs.cpp : : : $(CPP11) ;
+run result_value_construct3.cpp : : : $(CPP11) ;
+run result_error_construct3.cpp : : : $(CPP11) ;
+run result_emplace.cpp : : : $(CPP11) ;

test/constexpr_test2.cpp

@@ -0,0 +1,35 @@
+// Copyright 2022 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/system/error_code.hpp>
+#include <boost/config.hpp>
+#include <boost/config/pragma_message.hpp>
+
+#if defined(BOOST_GCC) && BOOST_GCC >= 40700 && BOOST_GCC < 40800
+
+BOOST_PRAGMA_MESSAGE("Skipping test, BOOST_GCC is 407xx")
+
+#else
+
+struct X
+{
+    boost::system::error_code ec;
+};
+
+X const& f()
+{
+#if defined(BOOST_CLANG_VERSION) && BOOST_CLANG_VERSION < 30900
+
+    BOOST_STATIC_CONSTEXPR X x = {};
+    return x;
+
+#else
+
+    BOOST_STATIC_CONSTEXPR X x;
+    return x;
+
+#endif
+}
+
+#endif

test/ec_hash_value_test.cpp

@@ -0,0 +1,132 @@
+// 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/system/generic_category.hpp>
+#include <boost/system/system_category.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <cerrno>
+#if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
+#include <system_error>
+#endif
+
+namespace sys = boost::system;
+
+int main()
+{
+    // normal against normal (equal, system)
+    {
+        sys::error_code e2( 0, sys::system_category() );
+        sys::error_code e3( e2.value(), e2.category() );
+
+        BOOST_TEST( e2 != e3 || hash_value( e2 ) == hash_value( e3 ) );
+        BOOST_TEST( e2 == e3 || hash_value( e2 ) != hash_value( e3 ) );
+    }
+
+    // normal against normal (equal, generic)
+    {
+        sys::error_code e2( EINVAL, sys::generic_category() );
+        sys::error_code e3( e2.value(), e2.category() );
+
+        BOOST_TEST( e2 != e3 || hash_value( e2 ) == hash_value( e3 ) );
+        BOOST_TEST( e2 == e3 || hash_value( e2 ) != hash_value( e3 ) );
+    }
+
+    // normal against normal (inequal, value, generic)
+    {
+        sys::error_code e2( 0, sys::generic_category() );
+        sys::error_code e3( EINVAL, sys::generic_category() );
+
+        BOOST_TEST( e2 != e3 || hash_value( e2 ) == hash_value( e3 ) );
+        BOOST_TEST( e2 == e3 || hash_value( e2 ) != hash_value( e3 ) );
+    }
+
+    // normal against normal (inequal, value, system)
+    {
+        sys::error_code e2( 1, sys::system_category() );
+        sys::error_code e3( 2, sys::system_category() );
+
+        BOOST_TEST( e2 != e3 || hash_value( e2 ) == hash_value( e3 ) );
+        BOOST_TEST( e2 == e3 || hash_value( e2 ) != hash_value( e3 ) );
+    }
+
+    // normal against normal (inequal, category)
+    {
+        sys::error_code e2( 0, sys::system_category() );
+        sys::error_code e3( 0, sys::generic_category() );
+
+        BOOST_TEST( e2 != e3 || hash_value( e2 ) == hash_value( e3 ) );
+        BOOST_TEST( e2 == e3 || hash_value( e2 ) != hash_value( e3 ) );
+    }
+
+    // empty against normal
+    {
+        sys::error_code e2;
+        sys::error_code e3( e2.value(), e2.category() );
+
+        BOOST_TEST( e2 != e3 || hash_value( e2 ) == hash_value( e3 ) );
+        BOOST_TEST( e2 == e3 || hash_value( e2 ) != hash_value( e3 ) );
+    }
+
+#if defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
+
+    // std:: wrapping against normal
+    {
+        std::error_code e1( EINVAL, std::generic_category() );
+
+        sys::error_code e2( e1 );
+        sys::error_code e3( e2.value(), e2.category() );
+
+        BOOST_TEST( e2 != e3 || hash_value( e2 ) == hash_value( e3 ) );
+        BOOST_TEST( e2 == e3 || hash_value( e2 ) != hash_value( e3 ) );
+    }
+
+    // empty against wrapping std:: empty
+    {
+        std::error_code e1;
+
+        sys::error_code e2( e1 );
+        sys::error_code e3;
+
+        BOOST_TEST( e2 != e3 || hash_value( e2 ) == hash_value( e3 ) );
+        BOOST_TEST( e2 == e3 || hash_value( e2 ) != hash_value( e3 ) );
+    }
+
+    // empty against roundtrip via std
+    {
+        sys::error_code e2;
+
+        std::error_code e1( e2 );
+        sys::error_code e3( e1 );
+
+        BOOST_TEST( e2 != e3 || hash_value( e2 ) == hash_value( e3 ) );
+        BOOST_TEST( e2 == e3 || hash_value( e2 ) != hash_value( e3 ) );
+    }
+
+    // normal/generic against roundtrip via std
+    {
+        sys::error_code e2( EINVAL, boost::system::generic_category() );
+
+        std::error_code e1( e2 );
+        sys::error_code e3( e1 );
+
+        BOOST_TEST( e2 != e3 || hash_value( e2 ) == hash_value( e3 ) );
+        BOOST_TEST( e2 == e3 || hash_value( e2 ) != hash_value( e3 ) );
+    }
+
+    // normal/system against roundtrip via std
+    {
+        sys::error_code e2( 0, boost::system::system_category() );
+
+        std::error_code e1( e2 );
+        sys::error_code e3( e1 );
+
+        BOOST_TEST( e2 != e3 || hash_value( e2 ) == hash_value( e3 ) );
+        BOOST_TEST( e2 == e3 || hash_value( e2 ) != hash_value( e3 ) );
+    }
+
+#endif
+
+    return boost::report_errors();
+}

test/error_code_test3.cpp

@@ -0,0 +1,69 @@
+// 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/system/error_condition.hpp>
+#include <boost/system/generic_category.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+namespace sys = boost::system;
+
+enum my_errc
+{
+    enomem_c = ENOMEM
+};
+
+enum my_errn
+{
+    enomem_n = ENOMEM
+};
+
+namespace boost {
+namespace system {
+
+template<> struct is_error_code_enum<my_errc>
+{
+    static const bool value = true;
+};
+
+template<> struct is_error_condition_enum<my_errn>
+{
+    static const bool value = true;
+};
+
+} // namespace system
+} // namespace boost
+
+sys::error_code make_error_code( my_errc e )
+{
+    return sys::error_code( e, sys::generic_category() );
+}
+
+sys::error_condition make_error_condition( my_errn e )
+{
+    return sys::error_condition( e, sys::generic_category() );
+}
+
+int main()
+{
+    sys::error_code ec = make_error_code( sys::errc::not_enough_memory );
+    sys::error_condition en( sys::errc::not_enough_memory );
+
+    BOOST_TEST_EQ( ec, en );
+    BOOST_TEST_EQ( en, ec );
+
+    BOOST_TEST_EQ( ec, enomem_c );
+    BOOST_TEST_EQ( enomem_c, ec );
+
+    BOOST_TEST_EQ( ec, enomem_n );
+    BOOST_TEST_EQ( enomem_n, ec );
+
+    BOOST_TEST_EQ( en, enomem_c );
+    BOOST_TEST_EQ( enomem_c, en );
+
+    BOOST_TEST_EQ( en, enomem_n );
+    BOOST_TEST_EQ( enomem_n, en );
+
+    return boost::report_errors();
+}

test/result_default_construct.cpp

@@ -12,6 +12,11 @@ struct X
 {
 };
 
+struct Y
+{
+    Y( int );
+};
+
 int main()
 {
     {
@@ -37,5 +42,17 @@ int main()
         BOOST_TEST( !r.has_error() );
     }
 
+    {
+        BOOST_TEST_TRAIT_TRUE((std::is_default_constructible<result<int>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_default_constructible<result<int, int>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_default_constructible<result<X>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_default_constructible<result<X, int>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_default_constructible<result<void>>));
+        BOOST_TEST_TRAIT_TRUE((std::is_default_constructible<result<void, int>>));
+
+        BOOST_TEST_TRAIT_FALSE((std::is_default_constructible<result<Y>>));
+        BOOST_TEST_TRAIT_FALSE((std::is_default_constructible<result<Y, int>>));
+    }
+
     return boost::report_errors();
 }

test/result_emplace.cpp

@@ -0,0 +1,176 @@
+// 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 <cerrno>
+
+using namespace boost::system;
+
+struct X
+{
+    static int instances;
+
+    int v_;
+
+    explicit X( int v ): v_( v ) { ++instances; }
+
+    X( int v1, int v2 ): v_( v1+v2 ) { ++instances; }
+    X( int v1, int v2, int v3 ): v_( v1+v2+v3 ) { ++instances; }
+
+    X( X const& ) = delete;
+    X& operator=( X const& ) = delete;
+
+    ~X() { --instances; }
+};
+
+int X::instances = 0;
+
+struct Y
+{
+    static int instances;
+
+    Y() noexcept { ++instances; }
+
+    Y( Y const& ) noexcept { ++instances; }
+
+    Y& operator=( Y const& ) = default;
+
+    ~Y() { --instances; }
+};
+
+int Y::instances = 0;
+
+int main()
+{
+    {
+        result<int> r;
+
+        BOOST_TEST( r.has_value() );
+
+        r.emplace( 1 );
+
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST_EQ( r.value(), 1 );
+    }
+
+    {
+        result<int> r( ENOENT, generic_category() );
+
+        BOOST_TEST( !r.has_value() );
+
+        r.emplace( 1 );
+
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST_EQ( r.value(), 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        result<X> r( 0 );
+
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST_EQ( r.value().v_, 0 );
+        BOOST_TEST_EQ( X::instances, 1 );
+
+        r.emplace( 1 );
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST_EQ( r.value().v_, 1 );
+        BOOST_TEST_EQ( X::instances, 1 );
+
+        r.emplace( 1, 2 );
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST_EQ( r.value().v_, 1+2 );
+        BOOST_TEST_EQ( X::instances, 1 );
+
+        r.emplace( 1, 2, 3 );
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST_EQ( r.value().v_, 1+2+3 );
+        BOOST_TEST_EQ( X::instances, 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        result<X> r( ENOENT, generic_category() );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST_EQ( X::instances, 0 );
+
+        r.emplace( 1, 2 );
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST_EQ( r.value().v_, 1+2 );
+        BOOST_TEST_EQ( X::instances, 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+    BOOST_TEST_EQ( Y::instances, 0 );
+
+    {
+        result<int, Y> r( Y{} );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST_EQ( Y::instances, 1 );
+
+        r.emplace( 1 );
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST_EQ( *r, 1 );
+        BOOST_TEST_EQ( Y::instances, 0 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+    BOOST_TEST_EQ( Y::instances, 0 );
+
+    {
+        result<X, Y> r( in_place_error );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST_EQ( X::instances, 0 );
+        BOOST_TEST_EQ( Y::instances, 1 );
+
+        r.emplace( 1, 2, 3 );
+
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST_EQ( r->v_, 1+2+3 );
+        BOOST_TEST_EQ( X::instances, 1 );
+        BOOST_TEST_EQ( Y::instances, 0 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+    BOOST_TEST_EQ( Y::instances, 0 );
+
+    {
+        result<void> r;
+
+        BOOST_TEST( r.has_value() );
+
+        r.emplace();
+        BOOST_TEST( r.has_value() );
+    }
+
+    {
+        result<void> r( ENOENT, generic_category() );
+
+        BOOST_TEST( !r.has_value() );
+
+        r.emplace();
+        BOOST_TEST( r.has_value() );
+    }
+
+    BOOST_TEST_EQ( Y::instances, 0 );
+
+    {
+        result<void, Y> r( in_place_error );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST_EQ( Y::instances, 1 );
+
+        r.emplace();
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST_EQ( Y::instances, 0 );
+    }
+
+    return boost::report_errors();
+}

test/result_error_construct3.cpp

@@ -0,0 +1,161 @@
+// 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 <string>
+#include <cerrno>
+
+using namespace boost::system;
+
+struct X
+{
+    static int instances;
+
+    int v_;
+
+    X(): v_() { ++instances; }
+
+    explicit X( int v ): v_( v ) { ++instances; }
+
+    X( int v1, int v2 ): v_( v1+v2 ) { ++instances; }
+    X( int v1, int v2, int v3 ): v_( v1+v2+v3 ) { ++instances; }
+
+    X( X const& r ): v_( r.v_ ) { ++instances; }
+
+    X& operator=( X const& ) = delete;
+
+    ~X() { --instances; }
+};
+
+int X::instances = 0;
+
+int main()
+{
+    {
+        auto ec = make_error_code( errc::invalid_argument );
+
+        using R = result<int>;
+        R r( R::in_place_error, ec );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_EQ( r.error(), ec );
+    }
+
+    {
+        using R = result<int>;
+        R r( R::in_place_error, EINVAL, generic_category() );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_EQ( r.error(), error_code( EINVAL, generic_category() ) );
+    }
+
+    {
+        auto ec = make_error_code( errc::invalid_argument );
+
+        using R = result<error_code>;
+        R r( R::in_place_error, ec );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_EQ( r.error(), ec );
+    }
+
+    {
+        using R = result<error_code>;
+        R r( R::in_place_error, EINVAL, generic_category() );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_EQ( r.error(), error_code( EINVAL, generic_category() ) );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        using R = result<std::string, X>;
+        R r( R::in_place_error, 1 );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_EQ( r.error().v_, 1 );
+
+        BOOST_TEST_EQ( X::instances, 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        using R = result<int, X>;
+        R r( R::in_place_error, 1, 2 );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_EQ( r.error().v_, 1+2 );
+
+        BOOST_TEST_EQ( X::instances, 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        using R = result<int, X>;
+        R r( R::in_place_error, 1, 2, 3 );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_EQ( r.error().v_, 1+2+3 );
+
+        BOOST_TEST_EQ( X::instances, 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        using R = result<X, X>;
+        R r( R::in_place_error, 1 );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_EQ( r.error().v_, 1 );
+
+        BOOST_TEST_EQ( X::instances, 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        auto ec = make_error_code( errc::invalid_argument );
+
+        using R = result<void>;
+        R r( R::in_place_error, ec );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_EQ( r.error(), ec );
+    }
+
+    {
+        using R = result<void>;
+        R r( R::in_place_error, EINVAL, generic_category() );
+
+        BOOST_TEST( !r.has_value() );
+        BOOST_TEST( r.has_error() );
+
+        BOOST_TEST_EQ( r.error(), error_code( EINVAL, generic_category() ) );
+    }
+
+    return boost::report_errors();
+}

test/result_typedefs.cpp

@@ -0,0 +1,22 @@
+// Copyright 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_trait.hpp>
+
+using namespace boost::system;
+
+struct X {};
+
+int main()
+{
+    BOOST_TEST_TRAIT_SAME( result<int>::value_type, int );
+    BOOST_TEST_TRAIT_SAME( result<X>::value_type, X );
+    BOOST_TEST_TRAIT_SAME( result<void>::value_type, void );
+
+    BOOST_TEST_TRAIT_SAME( result<int>::error_type, error_code );
+    BOOST_TEST_TRAIT_SAME( result<int, X>::error_type, X );
+
+    return boost::report_errors();
+}

test/result_value_access.cpp

@@ -5,6 +5,7 @@
 #include <boost/system/result.hpp>
 #include <boost/core/lightweight_test.hpp>
 #include <boost/core/lightweight_test_trait.hpp>
+#include <boost/config.hpp>
 #include <system_error>
 
 using namespace boost::system;
@@ -223,7 +224,10 @@ int main()
         BOOST_TEST_NOT( r );
         BOOST_TEST( !r );
 
+#if defined(BOOST_CLANG_VERSION) && BOOST_CLANG_VERSION < 30600
+#else
         BOOST_TEST_THROWS( r.value(), E2 );
+#endif
 
         BOOST_TEST_EQ( r.operator->(), static_cast<int*>(0) );
     }
@@ -471,7 +475,10 @@ int main()
         BOOST_TEST_NOT( r );
         BOOST_TEST( !r );
 
+#if defined(BOOST_CLANG_VERSION) && BOOST_CLANG_VERSION < 30600
+#else
         BOOST_TEST_THROWS( r.value(), E2 );
+#endif
 
         BOOST_TEST_EQ( r.operator->(), static_cast<void*>(0) );
     }

test/result_value_construct3.cpp

@@ -0,0 +1,118 @@
+// 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>
+
+using namespace boost::system;
+
+struct X
+{
+    static int instances;
+
+    int v_;
+
+    explicit X( int v ): v_( v ) { ++instances; }
+
+    X( int v1, int v2 ): v_( v1+v2 ) { ++instances; }
+    X( int v1, int v2, int v3 ): v_( v1+v2+v3 ) { ++instances; }
+
+    X( X const& ) = delete;
+    X& operator=( X const& ) = delete;
+
+    ~X() { --instances; }
+};
+
+int X::instances = 0;
+
+int main()
+{
+    {
+        using R = result<int>;
+        R r( R::in_place_value, 0 );
+
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST( !r.has_error() );
+
+        BOOST_TEST_EQ( r.value(), 0 );
+    }
+
+    {
+        using R = result<int, int>;
+        R r( R::in_place_value, 1 );
+
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST( !r.has_error() );
+
+        BOOST_TEST_EQ( *r, 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        using R = result<X>;
+        R r( R::in_place_value, 1 );
+
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST( !r.has_error() );
+
+        BOOST_TEST_EQ( r.value().v_, 1 );
+
+        BOOST_TEST_EQ( X::instances, 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        using R = result<X>;
+        R r( R::in_place_value, 1, 2 );
+
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST( !r.has_error() );
+
+        BOOST_TEST_EQ( r.value().v_, 1+2 );
+
+        BOOST_TEST_EQ( X::instances, 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        using R = result<X>;
+        R r( R::in_place_value, 1, 2, 3 );
+
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST( !r.has_error() );
+
+        BOOST_TEST_EQ( r.value().v_, 1+2+3 );
+
+        BOOST_TEST_EQ( X::instances, 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        using R = result<X, X>;
+        R r( R::in_place_value, 1 );
+
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST( !r.has_error() );
+
+        BOOST_TEST_EQ( r->v_, 1 );
+
+        BOOST_TEST_EQ( X::instances, 1 );
+    }
+
+    BOOST_TEST_EQ( X::instances, 0 );
+
+    {
+        using R = result<void>;
+        R r( R::in_place_value );
+
+        BOOST_TEST( r.has_value() );
+        BOOST_TEST( !r.has_error() );
+    }
+
+    return boost::report_errors();
+}

test/std_interop_test15.cpp

@@ -0,0 +1,94 @@
+// 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_condition.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/config/pragma_message.hpp>
+#include <boost/config.hpp>
+#include <boost/config/workaround.hpp>
+
+#if !defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
+
+BOOST_PRAGMA_MESSAGE( "BOOST_SYSTEM_HAS_SYSTEM_ERROR not defined, test will be skipped" )
+int main() {}
+
+#elif defined(BOOST_SYSTEM_AVOID_STD_GENERIC_CATEGORY)
+
+BOOST_PRAGMA_MESSAGE( "Skipping test, BOOST_SYSTEM_AVOID_STD_GENERIC_CATEGORY is defined" )
+int main() {}
+
+#else
+
+#include <system_error>
+
+namespace sys = boost::system;
+
+enum my_errc
+{
+    enomem_c = ENOMEM
+};
+
+enum my_errn
+{
+    enomem_n = ENOMEM
+};
+
+namespace std {
+
+template<> struct is_error_code_enum<my_errc>
+{
+    static const bool value = true;
+};
+
+template<> struct is_error_condition_enum<my_errn>
+{
+    static const bool value = true;
+};
+
+} // namespace std
+
+std::error_code make_error_code( my_errc e )
+{
+    return std::error_code( e, std::generic_category() );
+}
+
+std::error_condition make_error_condition( my_errn e )
+{
+    return std::error_condition( e, std::generic_category() );
+}
+
+int main()
+{
+    sys::error_code ec = make_error_code( sys::errc::not_enough_memory );
+    sys::error_condition en( sys::errc::not_enough_memory );
+
+    BOOST_TEST_EQ( ec, en );
+    BOOST_TEST_EQ( en, ec );
+
+    BOOST_TEST_EQ( ec, enomem_c );
+    BOOST_TEST_EQ( enomem_c, ec );
+
+    BOOST_TEST_EQ( ec, enomem_n );
+    BOOST_TEST_EQ( enomem_n, ec );
+
+    BOOST_TEST_EQ( en, enomem_c );
+    BOOST_TEST_EQ( enomem_c, en );
+
+#if BOOST_WORKAROUND(BOOST_MSVC, == 1800)
+
+    // msvc-12.0 has op== as a member of std::error_condition
+
+#else
+
+    BOOST_TEST_EQ( en, enomem_n );
+
+#endif
+
+    BOOST_TEST_EQ( enomem_n, en );
+
+    return boost::report_errors();
+}
+
+#endif

test/win32_generic_test.cpp

@@ -0,0 +1,52 @@
+// Copyright 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/config.hpp>
+#include <boost/config/pragma_message.hpp>
+
+#if !defined(BOOST_SYSTEM_HAS_SYSTEM_ERROR)
+
+BOOST_PRAGMA_MESSAGE( "Skipping test, BOOST_SYSTEM_HAS_SYSTEM_ERROR is not defined" )
+int main() {}
+
+#elif !defined(BOOST_MSSTL_VERSION) || BOOST_MSSTL_VERSION < 140
+
+BOOST_PRAGMA_MESSAGE( "Skipping test, BOOST_MSSTL_VERSION is not defined or is less than 140" )
+int main() {}
+
+#else
+
+#include <system_error>
+#include <iostream>
+
+int main()
+{
+    namespace sys = boost::system;
+
+    int n = 0;
+
+    for( int i = 0; i < 65000; ++i )
+    {
+        sys::error_code ec1( i, sys::system_category() );
+        sys::error_condition en1 = ec1.default_error_condition();
+
+        std::error_code ec2( i, std::system_category() );
+        std::error_condition en2 = ec2.default_error_condition();
+
+        if( en1 != en2 )
+        {
+            std::cout << i << ": " << en1 << " (" << en1.message() << ") != cond:" << en2.category().name() << ":" << en2.value() << " (" << en2.message() << ")\n";
+
+            if( en2.category() == std::generic_category() && i != 123 ) // msvc-14.0, msvc-14.1 disagree with us on ERROR_INVALID_NAME
+            {
+                ++n;
+            }
+        }
+    }
+
+    return n < 256 ? n: 255;
+}
+
+#endif