Remove C++11 requirements from test/Jamfile

Update .drone.jsonnet
Update ci.yml
2024-05-18 03:18:56 +03:00 · 2024-05-18 02:43:52 +03:00 · 2024-05-17 22:04:55 +03:00 · 2024-05-17 21:44:21 +03:00 · 2024-03-25 02:22:20 +02:00 · 2024-03-24 19:16:09 +02:00
41 changed files with 2680 additions and 262 deletions
--- a/.drone.jsonnet
+++ b/.drone.jsonnet
@ -0,0 +1,438 @@
+# Copyright 2022 Peter Dimov
+# Distributed under the Boost Software License, Version 1.0.
+# https://www.boost.org/LICENSE_1_0.txt
+
+local library = "variant2";
+
+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 16.04 GCC 4.8 32/64",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '11', ADDRMD: '32,64' },
+        "g++-4.8-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 GCC 4.9 32/64",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-4.9', CXXSTD: '11', ADDRMD: '32,64' },
+        "g++-4.9-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 GCC 5* 32/64",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '11,14', ADDRMD: '32,64' },
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 GCC 6 32/64",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-6', CXXSTD: '11,14', ADDRMD: '32,64' },
+        "g++-6-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 GCC 7* 32/64",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '11,14,17', ADDRMD: '32,64' },
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 GCC 8 32/64",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-8', CXXSTD: '11,14,17', ADDRMD: '32,64' },
+        "g++-8-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9* 32/64",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '11,14,17,2a', ADDRMD: '32,64' },
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9* ARM64",
+        "cppalliance/droneubuntu2004:multiarch",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '11,14,17,2a' },
+        arch="arm64",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 9* S390x",
+        "cppalliance/droneubuntu2004:multiarch",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '11,14,17,2a' },
+        arch="s390x",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 GCC 10 32/64",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-10', CXXSTD: '11,14,17,20', ADDRMD: '32,64' },
+        "g++-10-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 11* 32/64",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '11,14,17,2a', ADDRMD: '32,64' },
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 GCC 12 32/64",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '11,14,17,20,2b', ADDRMD: '32,64' },
+        "g++-12-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 23.04 GCC 13 32 ASAN",
+        "cppalliance/droneubuntu2304:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-13', CXXSTD: '11,14,17,20,2b', ADDRMD: '32' } + asan,
+        "g++-13-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 23.04 GCC 13 64 ASAN",
+        "cppalliance/droneubuntu2304:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-13', CXXSTD: '11,14,17,20,2b', ADDRMD: '64' } + asan,
+        "g++-13-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 23.04 GCC 13 32 UBSAN",
+        "cppalliance/droneubuntu2304:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-13', CXXSTD: '11,14,17,20,2b', ADDRMD: '32' } + ubsan,
+        "g++-13-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 23.04 GCC 13 64 UBSAN",
+        "cppalliance/droneubuntu2304:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-13', CXXSTD: '11,14,17,20,2b', ADDRMD: '64' } + ubsan,
+        "g++-13-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 24.04 GCC 14 32",
+        "cppalliance/droneubuntu2404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-14', CXXSTD: '11,14,17,20,2b', ADDRMD: '32' },
+        "g++-14-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 24.04 GCC 14 64",
+        "cppalliance/droneubuntu2404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-14', CXXSTD: '11,14,17,20,2b', ADDRMD: '64' },
+        "g++-14-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 Clang 3.5",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.5', CXXSTD: '11' },
+        "clang-3.5",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 Clang 3.6",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.6', CXXSTD: '11,14' },
+        "clang-3.6",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 Clang 3.7",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.7', CXXSTD: '11,14' },
+        "clang-3.7",
+    ),
+
+    linux_pipeline(
+        "Linux 16.04 Clang 3.8",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.8', CXXSTD: '11,14' },
+        "clang-3.8",
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 Clang 3.9",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-3.9', CXXSTD: '11,14' },
+        "clang-3.9",
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 Clang 4.0",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-4.0', CXXSTD: '11,14' },
+        "clang-4.0",
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 Clang 5.0",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-5.0', CXXSTD: '11,14,1z' },
+        "clang-5.0",
+    ),
+
+    linux_pipeline(
+        "Linux 18.04 Clang 6.0",
+        "cppalliance/droneubuntu1804:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-6.0', CXXSTD: '11,14,17' },
+        "clang-6.0",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 7",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-7', CXXSTD: '11,14,17' },
+        "clang-7",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 8",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-8', CXXSTD: '11,14,17' },
+        "clang-8",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 9",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-9', CXXSTD: '11,14,17,2a' },
+        "clang-9",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 10",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-10', CXXSTD: '11,14,17,2a' },
+        "clang-10",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 11",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-11', CXXSTD: '11,14,17,2a' },
+        "clang-11",
+    ),
+
+    linux_pipeline(
+        "Linux 20.04 Clang 12",
+        "cppalliance/droneubuntu2004:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-12', CXXSTD: '11,14,17,2a' },
+        "clang-12",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 Clang 13",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-13', CXXSTD: '11,14,17,20,2b' },
+        "clang-13",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 Clang 14",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-14', CXXSTD: '11,14,17,20,2b' },
+        "clang-14",
+    ),
+
+    linux_pipeline(
+        "Linux 22.04 Clang 15",
+        "cppalliance/droneubuntu2204:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-15', CXXSTD: '11,14,17,20,2b' },
+        "clang-15",
+    ),
+
+    linux_pipeline(
+        "Linux 23.04 Clang 16",
+        "cppalliance/droneubuntu2304:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-16', CXXSTD: '11,14,17,20,2b' },
+        "clang-16",
+    ),
+
+    linux_pipeline(
+        "Linux 23.10 Clang 17 UBSAN",
+        "cppalliance/droneubuntu2310:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-17', CXXSTD: '11,14,17,20,2b' } + ubsan,
+        "clang-17",
+    ),
+
+    linux_pipeline(
+        "Linux 23.10 Clang 17 ASAN",
+        "cppalliance/droneubuntu2310:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-17', CXXSTD: '11,14,17,20,2b' } + asan,
+        "clang-17",
+    ),
+
+    linux_pipeline(
+        "Linux 24.04 Clang 18 UBSAN",
+        "cppalliance/droneubuntu2404:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-18', CXXSTD: '11,14,17,20,2b' } + ubsan,
+        "clang-18",
+    ),
+
+    linux_pipeline(
+        "Linux 24.04 Clang 18 ASAN",
+        "cppalliance/droneubuntu2404:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-18', CXXSTD: '11,14,17,20,2b' } + asan,
+        "clang-18",
+    ),
+
+    macos_pipeline(
+        "MacOS 10.15 Xcode 12.2 UBSAN",
+        { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '11,14,1z' } + ubsan,
+    ),
+
+    macos_pipeline(
+        "MacOS 10.15 Xcode 12.2 ASAN",
+        { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '11,14,1z' } + asan,
+    ),
+
+    macos_pipeline(
+        "MacOS 12.4 Xcode 13.4.1 UBSAN",
+        { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '11,14,17,20,2b' } + ubsan,
+        xcode_version = "13.4.1", osx_version = "monterey", arch = "arm64",
+    ),
+
+    macos_pipeline(
+        "MacOS 12.4 Xcode 13.4.1 ASAN",
+        { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '11,14,17,20,2b' } + asan,
+        xcode_version = "13.4.1", osx_version = "monterey", arch = "arm64",
+    ),
+
+    windows_pipeline(
+        "Windows VS2015 msvc-14.0",
+        "cppalliance/dronevs2015",
+        { TOOLSET: 'msvc-14.0', CXXSTD: '14,latest', B2_DONT_EMBED_MANIFEST: '1' },
+    ),
+
+    windows_pipeline(
+        "Windows VS2017 msvc-14.1",
+        "cppalliance/dronevs2017",
+        { TOOLSET: 'msvc-14.1', CXXSTD: '14,17,latest' },
+    ),
+
+    windows_pipeline(
+        "Windows VS2017 msvc-14.1 permissive-",
+        "cppalliance/dronevs2017",
+        { TOOLSET: 'msvc-14.1', CXXSTD: '14,17', CXXFLAGS: '/permissive-' },
+    ),
+
+    windows_pipeline(
+        "Windows VS2019 msvc-14.2",
+        "cppalliance/dronevs2019",
+        { TOOLSET: 'msvc-14.2', CXXSTD: '14,17,20,latest' },
+    ),
+
+    windows_pipeline(
+        "Windows VS2019 msvc-14.2 permissive-",
+        "cppalliance/dronevs2019",
+        { TOOLSET: 'msvc-14.2', CXXSTD: '14,17', CXXFLAGS: '/permissive-' },
+    ),
+
+    windows_pipeline(
+        "Windows VS2022 msvc-14.3",
+        "cppalliance/dronevs2022:1",
+        { TOOLSET: 'msvc-14.3', CXXSTD: '14,17,20,latest' },
+    ),
+
+    windows_pipeline(
+        "Windows VS2022 msvc-14.3 permissive-",
+        "cppalliance/dronevs2022:1",
+        { TOOLSET: 'msvc-14.3', CXXSTD: '14,17', CXXFLAGS: '/permissive-' },
+    ),
+]
--- a/.drone/drone.bat
+++ b/.drone/drone.bat
@ -0,0 +1,24 @@
+@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%
+if not "%CXXFLAGS%" == "" set CXXFLAGS=cxxflags=%CXXFLAGS%
+b2 -j3 libs/%LIBRARY%/test toolset=%TOOLSET% %CXXSTD% %ADDRMD% %CXXFLAGS% variant=debug,release embed-manifest-via=linker
--- a/.drone/drone.sh
+++ b/.drone/drone.sh
@ -0,0 +1,25 @@
+#!/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
+export PATH=~/.local/bin:/usr/local/bin:$PATH
+
+DRONE_BUILD_DIR=$(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}
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@ -0,0 +1,628 @@
+name: CI
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+      - develop
+      - feature/**
+
+env:
+  UBSAN_OPTIONS: print_stacktrace=1
+
+jobs:
+  posix:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - toolset: gcc-4.8
+            cxxstd: "11"
+            container: ubuntu:16.04
+            os: ubuntu-latest
+            install: g++-4.8
+          - toolset: gcc-4.9
+            cxxstd: "11"
+            container: ubuntu:16.04
+            os: ubuntu-latest
+            install: g++-4.9
+          - toolset: gcc-5
+            cxxstd: "11,14,1z"
+            container: ubuntu:18.04
+            os: ubuntu-latest
+            install: g++-5
+          - toolset: gcc-6
+            cxxstd: "11,14,1z"
+            container: ubuntu:18.04
+            os: ubuntu-latest
+            install: g++-6
+          - toolset: gcc-7
+            cxxstd: "11,14,17"
+            container: ubuntu:18.04
+            os: ubuntu-latest
+          - toolset: gcc-8
+            cxxstd: "11,14,17,2a"
+            os: ubuntu-20.04
+            install: g++-8
+          - toolset: gcc-9
+            cxxstd: "11,14,17,2a"
+            os: ubuntu-20.04
+          - toolset: gcc-10
+            cxxstd: "11,14,17,2a"
+            os: ubuntu-22.04
+            install: g++-10
+          - toolset: gcc-11
+            cxxstd: "11,14,17,2a"
+            os: ubuntu-22.04
+            install: g++-11
+          - toolset: gcc-12
+            cxxstd: "11,14,17,20,2b"
+            os: ubuntu-22.04
+            install: g++-12
+          - toolset: gcc-13
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:23.04
+            os: ubuntu-latest
+            install: g++-13
+          - toolset: gcc-14
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:24.04
+            os: ubuntu-latest
+            install: g++-14
+          - toolset: clang
+            compiler: clang++-3.9
+            cxxstd: "11,14"
+            container: ubuntu:18.04
+            os: ubuntu-latest
+            install: clang-3.9
+          - toolset: clang
+            compiler: clang++-4.0
+            cxxstd: "11,14"
+            container: ubuntu:18.04
+            os: ubuntu-latest
+            install: clang-4.0
+          - toolset: clang
+            compiler: clang++-5.0
+            cxxstd: "11,14,1z"
+            container: ubuntu:18.04
+            os: ubuntu-latest
+            install: clang-5.0
+          - toolset: clang
+            compiler: clang++-6.0
+            cxxstd: "11,14,17"
+            os: ubuntu-20.04
+            install: clang-6.0
+          - toolset: clang
+            compiler: clang++-7
+            cxxstd: "11,14,17"
+            os: ubuntu-20.04
+            install: clang-7
+          - toolset: clang
+            compiler: clang++-8
+            cxxstd: "11,14,17"
+            os: ubuntu-20.04
+            install: clang-8
+          - toolset: clang
+            compiler: clang++-9
+            cxxstd: "11,14,17,2a"
+            os: ubuntu-20.04
+            install: clang-9
+          - toolset: clang
+            compiler: clang++-10
+            cxxstd: "11,14,17,2a"
+            os: ubuntu-20.04
+            install: clang-10
+          - toolset: clang
+            compiler: clang++-11
+            cxxstd: "11,14,17,2a"
+            os: ubuntu-20.04
+            install: clang-11
+          - toolset: clang
+            compiler: clang++-12
+            cxxstd: "11,14,17,2a"
+            os: ubuntu-20.04
+            install: clang-12
+          - toolset: clang
+            compiler: clang++-13
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:22.04
+            os: ubuntu-latest
+            install: clang-13
+          - toolset: clang
+            compiler: clang++-14
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:22.04
+            os: ubuntu-latest
+            install: clang-14
+          - toolset: clang
+            compiler: clang++-15
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:22.04
+            os: ubuntu-latest
+            install: clang-15
+          - toolset: clang
+            compiler: clang++-16
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:23.04
+            os: ubuntu-latest
+            install: clang-16
+          - toolset: clang
+            compiler: clang++-17
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:23.10
+            os: ubuntu-latest
+            install: clang-17
+          - toolset: clang
+            compiler: clang++-18
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:24.04
+            os: ubuntu-latest
+            install: clang-18
+          - toolset: clang
+            cxxstd: "11,14,17,2a"
+            os: macos-11
+          - toolset: clang
+            cxxstd: "11,14,17,20,2b"
+            os: macos-12
+          - toolset: clang
+            cxxstd: "11,14,17,20,2b"
+            os: macos-13
+          - toolset: clang
+            cxxstd: "11,14,17,20,2b"
+            os: macos-14
+
+    runs-on: ${{matrix.os}}
+    container: ${{matrix.container}}
+
+    defaults:
+      run:
+        shell: bash
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Setup container environment
+        if: matrix.container
+        run: |
+          apt-get update
+          apt-get -y install sudo python3 git g++
+
+      - name: Install packages
+        if: matrix.install
+        run: |
+          sudo apt-get update
+          sudo apt-get -y install ${{matrix.install}}
+
+      - name: Setup Boost
+        run: |
+          echo GITHUB_REPOSITORY: $GITHUB_REPOSITORY
+          LIBRARY=${GITHUB_REPOSITORY#*/}
+          echo LIBRARY: $LIBRARY
+          echo "LIBRARY=$LIBRARY" >> $GITHUB_ENV
+          echo GITHUB_BASE_REF: $GITHUB_BASE_REF
+          echo GITHUB_REF: $GITHUB_REF
+          REF=${GITHUB_BASE_REF:-$GITHUB_REF}
+          REF=${REF#refs/heads/}
+          echo REF: $REF
+          BOOST_BRANCH=develop && [ "$REF" == "master" ] && BOOST_BRANCH=master || true
+          echo BOOST_BRANCH: $BOOST_BRANCH
+          cd ..
+          git clone -b $BOOST_BRANCH --depth 1 https://github.com/boostorg/boost.git boost-root
+          cd boost-root
+          cp -r $GITHUB_WORKSPACE/* libs/$LIBRARY
+          git submodule update --init tools/boostdep
+          python3 tools/boostdep/depinst/depinst.py $LIBRARY
+          ./bootstrap.sh
+          ./b2 -d0 headers
+
+      - name: Create user-config.jam
+        if: matrix.compiler
+        run: |
+          echo "using ${{matrix.toolset}} : : ${{matrix.compiler}} ;" > ~/user-config.jam
+
+      - name: Run tests
+        run: |
+          cd ../boost-root
+          ./b2 -j3 libs/$LIBRARY/test toolset=${{matrix.toolset}} cxxstd=${{matrix.cxxstd}} variant=debug,release
+
+  windows:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - toolset: msvc-14.0
+            cxxstd: "14,latest"
+            addrmd: 32,64
+            os: windows-2019
+          - toolset: msvc-14.2
+            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
+          - toolset: gcc
+            cxxstd: "11,14,17,2a"
+            addrmd: 64
+            os: windows-2019
+
+    runs-on: ${{matrix.os}}
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Boost
+        shell: cmd
+        run: |
+          echo GITHUB_REPOSITORY: %GITHUB_REPOSITORY%
+          for /f %%i in ("%GITHUB_REPOSITORY%") do set LIBRARY=%%~nxi
+          echo LIBRARY: %LIBRARY%
+          echo LIBRARY=%LIBRARY%>>%GITHUB_ENV%
+          echo GITHUB_BASE_REF: %GITHUB_BASE_REF%
+          echo GITHUB_REF: %GITHUB_REF%
+          if "%GITHUB_BASE_REF%" == "" set GITHUB_BASE_REF=%GITHUB_REF%
+          set BOOST_BRANCH=develop
+          for /f %%i in ("%GITHUB_BASE_REF%") do if "%%~nxi" == "master" set BOOST_BRANCH=master
+          echo BOOST_BRANCH: %BOOST_BRANCH%
+          cd ..
+          git clone -b %BOOST_BRANCH% --depth 1 https://github.com/boostorg/boost.git boost-root
+          cd boost-root
+          xcopy /s /e /q %GITHUB_WORKSPACE% libs\%LIBRARY%\
+          git submodule update --init tools/boostdep
+          python tools/boostdep/depinst/depinst.py --git_args "--jobs 3" %LIBRARY%
+          cmd /c bootstrap
+          b2 -d0 headers
+
+      - name: Run tests
+        shell: cmd
+        run: |
+          cd ../boost-root
+          b2 -j3 libs/%LIBRARY%/test toolset=${{matrix.toolset}} cxxstd=${{matrix.cxxstd}} address-model=${{matrix.addrmd}} variant=debug,release embed-manifest-via=linker
+
+  posix-cmake-subdir:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: ubuntu-20.04
+          - os: ubuntu-22.04
+          - os: macos-11
+          - os: macos-12
+          - os: macos-13
+
+    runs-on: ${{matrix.os}}
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install packages
+        if: matrix.install
+        run: sudo apt-get -y install ${{matrix.install}}
+
+      - name: Setup Boost
+        run: |
+          echo GITHUB_REPOSITORY: $GITHUB_REPOSITORY
+          LIBRARY=${GITHUB_REPOSITORY#*/}
+          echo LIBRARY: $LIBRARY
+          echo "LIBRARY=$LIBRARY" >> $GITHUB_ENV
+          echo GITHUB_BASE_REF: $GITHUB_BASE_REF
+          echo GITHUB_REF: $GITHUB_REF
+          REF=${GITHUB_BASE_REF:-$GITHUB_REF}
+          REF=${REF#refs/heads/}
+          echo REF: $REF
+          BOOST_BRANCH=develop && [ "$REF" == "master" ] && BOOST_BRANCH=master || true
+          echo BOOST_BRANCH: $BOOST_BRANCH
+          cd ..
+          git clone -b $BOOST_BRANCH --depth 1 https://github.com/boostorg/boost.git boost-root
+          cd boost-root
+          cp -r $GITHUB_WORKSPACE/* libs/$LIBRARY
+          git submodule update --init tools/boostdep
+          python tools/boostdep/depinst/depinst.py --git_args "--jobs 3" $LIBRARY
+
+      - name: Use library with add_subdirectory
+        run: |
+          cd ../boost-root/libs/$LIBRARY/test/cmake_subdir_test
+          mkdir __build__ && cd __build__
+          cmake ..
+          cmake --build .
+          ctest --output-on-failure --no-tests=error
+
+  posix-cmake-install:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: ubuntu-20.04
+          - os: ubuntu-22.04
+          - os: macos-11
+          - os: macos-12
+          - os: macos-13
+
+    runs-on: ${{matrix.os}}
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install packages
+        if: matrix.install
+        run: sudo apt-get -y install ${{matrix.install}}
+
+      - name: Setup Boost
+        run: |
+          echo GITHUB_REPOSITORY: $GITHUB_REPOSITORY
+          LIBRARY=${GITHUB_REPOSITORY#*/}
+          echo LIBRARY: $LIBRARY
+          echo "LIBRARY=$LIBRARY" >> $GITHUB_ENV
+          echo GITHUB_BASE_REF: $GITHUB_BASE_REF
+          echo GITHUB_REF: $GITHUB_REF
+          REF=${GITHUB_BASE_REF:-$GITHUB_REF}
+          REF=${REF#refs/heads/}
+          echo REF: $REF
+          BOOST_BRANCH=develop && [ "$REF" == "master" ] && BOOST_BRANCH=master || true
+          echo BOOST_BRANCH: $BOOST_BRANCH
+          cd ..
+          git clone -b $BOOST_BRANCH --depth 1 https://github.com/boostorg/boost.git boost-root
+          cd boost-root
+          cp -r $GITHUB_WORKSPACE/* libs/$LIBRARY
+          git submodule update --init tools/boostdep
+          python tools/boostdep/depinst/depinst.py --git_args "--jobs 3" $LIBRARY
+
+      - name: Configure
+        run: |
+          cd ../boost-root
+          mkdir __build__ && cd __build__
+          cmake -DBOOST_INCLUDE_LIBRARIES=$LIBRARY -DCMAKE_INSTALL_PREFIX=~/.local ..
+
+      - name: Install
+        run: |
+          cd ../boost-root/__build__
+          cmake --build . --target install
+
+      - name: Use the installed library
+        run: |
+          cd ../boost-root/libs/$LIBRARY/test/cmake_install_test && mkdir __build__ && cd __build__
+          cmake -DCMAKE_INSTALL_PREFIX=~/.local ..
+          cmake --build .
+          ctest --output-on-failure --no-tests=error
+
+  posix-cmake-test:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: ubuntu-20.04
+          - os: ubuntu-22.04
+          - os: macos-11
+          - os: macos-12
+          - os: macos-13
+
+    runs-on: ${{matrix.os}}
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install packages
+        if: matrix.install
+        run: sudo apt-get -y install ${{matrix.install}}
+
+      - name: Setup Boost
+        run: |
+          echo GITHUB_REPOSITORY: $GITHUB_REPOSITORY
+          LIBRARY=${GITHUB_REPOSITORY#*/}
+          echo LIBRARY: $LIBRARY
+          echo "LIBRARY=$LIBRARY" >> $GITHUB_ENV
+          echo GITHUB_BASE_REF: $GITHUB_BASE_REF
+          echo GITHUB_REF: $GITHUB_REF
+          REF=${GITHUB_BASE_REF:-$GITHUB_REF}
+          REF=${REF#refs/heads/}
+          echo REF: $REF
+          BOOST_BRANCH=develop && [ "$REF" == "master" ] && BOOST_BRANCH=master || true
+          echo BOOST_BRANCH: $BOOST_BRANCH
+          cd ..
+          git clone -b $BOOST_BRANCH --depth 1 https://github.com/boostorg/boost.git boost-root
+          cd boost-root
+          cp -r $GITHUB_WORKSPACE/* libs/$LIBRARY
+          git submodule update --init tools/boostdep
+          python tools/boostdep/depinst/depinst.py --git_args "--jobs 3" $LIBRARY
+
+      - name: Configure
+        run: |
+          cd ../boost-root
+          mkdir __build__ && cd __build__
+          cmake -DBOOST_INCLUDE_LIBRARIES=$LIBRARY -DBUILD_TESTING=ON ..
+
+      - name: Build tests
+        run: |
+          cd ../boost-root/__build__
+          cmake --build . --target tests
+
+      - name: Run tests
+        run: |
+          cd ../boost-root/__build__
+          ctest --output-on-failure --no-tests=error
+
+  windows-cmake-subdir:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: windows-2019
+          - os: windows-2022
+
+    runs-on: ${{matrix.os}}
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Boost
+        shell: cmd
+        run: |
+          echo GITHUB_REPOSITORY: %GITHUB_REPOSITORY%
+          for /f %%i in ("%GITHUB_REPOSITORY%") do set LIBRARY=%%~nxi
+          echo LIBRARY: %LIBRARY%
+          echo LIBRARY=%LIBRARY%>>%GITHUB_ENV%
+          echo GITHUB_BASE_REF: %GITHUB_BASE_REF%
+          echo GITHUB_REF: %GITHUB_REF%
+          if "%GITHUB_BASE_REF%" == "" set GITHUB_BASE_REF=%GITHUB_REF%
+          set BOOST_BRANCH=develop
+          for /f %%i in ("%GITHUB_BASE_REF%") do if "%%~nxi" == "master" set BOOST_BRANCH=master
+          echo BOOST_BRANCH: %BOOST_BRANCH%
+          cd ..
+          git clone -b %BOOST_BRANCH% --depth 1 https://github.com/boostorg/boost.git boost-root
+          cd boost-root
+          xcopy /s /e /q %GITHUB_WORKSPACE% libs\%LIBRARY%\
+          git submodule update --init tools/boostdep
+          python tools/boostdep/depinst/depinst.py --git_args "--jobs 3" %LIBRARY%
+
+      - name: Use library with add_subdirectory (Debug)
+        shell: cmd
+        run: |
+          cd ../boost-root/libs/%LIBRARY%/test/cmake_subdir_test
+          mkdir __build__ && cd __build__
+          cmake ..
+          cmake --build . --config Debug
+          ctest --output-on-failure --no-tests=error -C Debug
+
+      - name: Use library with add_subdirectory (Release)
+        shell: cmd
+        run: |
+          cd ../boost-root/libs/%LIBRARY%/test/cmake_subdir_test/__build__
+          cmake --build . --config Release
+          ctest --output-on-failure --no-tests=error -C Release
+
+  windows-cmake-install:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: windows-2019
+          - os: windows-2022
+
+    runs-on: ${{matrix.os}}
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Boost
+        shell: cmd
+        run: |
+          echo GITHUB_REPOSITORY: %GITHUB_REPOSITORY%
+          for /f %%i in ("%GITHUB_REPOSITORY%") do set LIBRARY=%%~nxi
+          echo LIBRARY: %LIBRARY%
+          echo LIBRARY=%LIBRARY%>>%GITHUB_ENV%
+          echo GITHUB_BASE_REF: %GITHUB_BASE_REF%
+          echo GITHUB_REF: %GITHUB_REF%
+          if "%GITHUB_BASE_REF%" == "" set GITHUB_BASE_REF=%GITHUB_REF%
+          set BOOST_BRANCH=develop
+          for /f %%i in ("%GITHUB_BASE_REF%") do if "%%~nxi" == "master" set BOOST_BRANCH=master
+          echo BOOST_BRANCH: %BOOST_BRANCH%
+          cd ..
+          git clone -b %BOOST_BRANCH% --depth 1 https://github.com/boostorg/boost.git boost-root
+          cd boost-root
+          xcopy /s /e /q %GITHUB_WORKSPACE% libs\%LIBRARY%\
+          git submodule update --init tools/boostdep
+          python tools/boostdep/depinst/depinst.py --git_args "--jobs 3" %LIBRARY%
+
+      - name: Configure
+        shell: cmd
+        run: |
+          cd ../boost-root
+          mkdir __build__ && cd __build__
+          cmake -DBOOST_INCLUDE_LIBRARIES=%LIBRARY% -DCMAKE_INSTALL_PREFIX=C:/cmake-prefix ..
+
+      - name: Install (Debug)
+        shell: cmd
+        run: |
+          cd ../boost-root/__build__
+          cmake --build . --target install --config Debug
+
+      - name: Install (Release)
+        shell: cmd
+        run: |
+          cd ../boost-root/__build__
+          cmake --build . --target install --config Release
+
+      - name: Use the installed library (Debug)
+        shell: cmd
+        run: |
+          cd ../boost-root/libs/%LIBRARY%/test/cmake_install_test && mkdir __build__ && cd __build__
+          cmake -DCMAKE_INSTALL_PREFIX=C:/cmake-prefix ..
+          cmake --build . --config Debug
+          ctest --output-on-failure --no-tests=error -C Debug
+
+      - name: Use the installed library (Release)
+        shell: cmd
+        run: |
+          cd ../boost-root/libs/%LIBRARY%/test/cmake_install_test/__build__
+          cmake --build . --config Release
+          ctest --output-on-failure --no-tests=error -C Release
+
+  windows-cmake-test:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: windows-2019
+          - os: windows-2022
+
+    runs-on: ${{matrix.os}}
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Boost
+        shell: cmd
+        run: |
+          echo GITHUB_REPOSITORY: %GITHUB_REPOSITORY%
+          for /f %%i in ("%GITHUB_REPOSITORY%") do set LIBRARY=%%~nxi
+          echo LIBRARY: %LIBRARY%
+          echo LIBRARY=%LIBRARY%>>%GITHUB_ENV%
+          echo GITHUB_BASE_REF: %GITHUB_BASE_REF%
+          echo GITHUB_REF: %GITHUB_REF%
+          if "%GITHUB_BASE_REF%" == "" set GITHUB_BASE_REF=%GITHUB_REF%
+          set BOOST_BRANCH=develop
+          for /f %%i in ("%GITHUB_BASE_REF%") do if "%%~nxi" == "master" set BOOST_BRANCH=master
+          echo BOOST_BRANCH: %BOOST_BRANCH%
+          cd ..
+          git clone -b %BOOST_BRANCH% --depth 1 https://github.com/boostorg/boost.git boost-root
+          cd boost-root
+          xcopy /s /e /q %GITHUB_WORKSPACE% libs\%LIBRARY%\
+          git submodule update --init tools/boostdep
+          python tools/boostdep/depinst/depinst.py --git_args "--jobs 3" %LIBRARY%
+
+      - name: Configure
+        shell: cmd
+        run: |
+          cd ../boost-root
+          mkdir __build__ && cd __build__
+          cmake -DBOOST_INCLUDE_LIBRARIES=%LIBRARY% -DBUILD_TESTING=ON ..
+
+      - name: Build tests (Debug)
+        shell: cmd
+        run: |
+          cd ../boost-root/__build__
+          cmake --build . --target tests --config Debug
+
+      - name: Run tests (Debug)
+        shell: cmd
+        run: |
+          cd ../boost-root/__build__
+          ctest --output-on-failure --no-tests=error -C Debug
+
+      - name: Build tests (Release)
+        shell: cmd
+        run: |
+          cd ../boost-root/__build__
+          cmake --build . --target tests --config Release
+
+      - name: Run tests (Release)
+        shell: cmd
+        run: |
+          cd ../boost-root/__build__
+          ctest --output-on-failure --no-tests=error -C Release
--- a/.travis.yml
+++ b/.travis.yml
@ -1,4 +1,4 @@
-# Copyright 2016-2019 Peter Dimov
+# Copyright 2016-2021 Peter Dimov
 # Distributed under the Boost Software License, Version 1.0.
 # (See accompanying file LICENSE_1_0.txt or copy at http://boost.org/LICENSE_1_0.txt)

@ -95,7 +95,7 @@ matrix:
    - os: linux
      dist: bionic
      compiler: g++-10
-      env: TOOLSET=gcc COMPILER=g++-10 CXXSTD=11,14,17,2a
+      env: UBSAN=1 TOOLSET=gcc COMPILER=g++-10 CXXSTD=11,14,17,2a UBSAN_OPTIONS=print_stacktrace=1 LINKFLAGS=-fuse-ld=gold
      addons:
        apt:
          packages:
@ -103,21 +103,6 @@ matrix:
          sources:
            - ubuntu-toolchain-r-test

-    - os: linux
-      compiler: g++-8
-      env: UBSAN=1 TOOLSET=gcc COMPILER=g++-8 CXXSTD=11,14,17,2a UBSAN_OPTIONS=print_stacktrace=1 LINKFLAGS=-fuse-ld=gold
-      addons:
-        apt:
-          packages:
-            - g++-8
-          sources:
-            - ubuntu-toolchain-r-test
-
-    - os: linux
-      dist: trusty
-      compiler: clang++
-      env: DIST=trusty TOOLSET=clang COMPILER=clang++ CXXSTD=11,14,1z
-
    - os: linux
      compiler: clang++-3.5
      env: TOOLSET=clang COMPILER=clang++-3.5 CXXSTD=11,14,1z
@ -180,6 +165,7 @@ matrix:
            - ubuntu-toolchain-r-test

    - os: linux
+      dist: bionic
      compiler: clang++-5.0
      env: TOOLSET=clang COMPILER=clang++-5.0 CXXSTD=11,14,1z
      addons:
@ -190,6 +176,7 @@ matrix:
            - ubuntu-toolchain-r-test

    - os: linux
+      dist: bionic
      compiler: clang++-6.0
      env: TOOLSET=clang COMPILER=clang++-6.0 CXXSTD=11,14,17
      addons:
@ -200,6 +187,7 @@ matrix:
            - ubuntu-toolchain-r-test

    - os: linux
+      dist: bionic
      compiler: clang++-7
      env: TOOLSET=clang COMPILER=clang++-7 CXXSTD=11,14,17,2a
      addons:
@ -208,9 +196,10 @@ matrix:
            - clang-7
          sources:
            - ubuntu-toolchain-r-test
-            - llvm-toolchain-xenial-7
+            - llvm-toolchain-bionic-7

    - os: linux
+      dist: bionic
      compiler: clang++-8
      env: TOOLSET=clang COMPILER=clang++-8 CXXSTD=11,14,17,2a
      addons:
@ -219,10 +208,10 @@ matrix:
            - clang-8
          sources:
            - ubuntu-toolchain-r-test
-            - llvm-toolchain-xenial-8
+            - llvm-toolchain-bionic-8

    - os: linux
-      dist: xenial
+      dist: bionic
      compiler: clang++-9
      env: TOOLSET=clang COMPILER=clang++-9 CXXSTD=11,14,17,2a
      addons:
@ -231,11 +220,11 @@ matrix:
            - clang-9
          sources:
            - ubuntu-toolchain-r-test
-            - sourceline: 'deb https://apt.llvm.org/xenial/ llvm-toolchain-xenial-9 main'
+            - sourceline: 'deb https://apt.llvm.org/bionic/ llvm-toolchain-bionic-9 main'
              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'

    - os: linux
-      dist: xenial
+      dist: bionic
      compiler: clang++-10
      env: TOOLSET=clang COMPILER=clang++-10 CXXSTD=11,14,17,2a
      addons:
@ -244,19 +233,34 @@ matrix:
            - clang-10
          sources:
            - ubuntu-toolchain-r-test
-            - sourceline: 'deb https://apt.llvm.org/xenial/ llvm-toolchain-xenial-10 main'
+            - sourceline: 'deb https://apt.llvm.org/bionic/ llvm-toolchain-bionic-10 main'
              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'

    - os: linux
-      compiler: clang++-8
-      env: UBSAN=1 TOOLSET=clang COMPILER=clang++-8 CXXSTD=11,14,17,2a UBSAN_OPTIONS=print_stacktrace=1
+      dist: bionic
+      compiler: clang++-11
+      env: TOOLSET=clang COMPILER=clang++-11 CXXSTD=11,14,17,2a
      addons:
        apt:
          packages:
-            - clang-8
+            - clang-11
          sources:
            - ubuntu-toolchain-r-test
-            - llvm-toolchain-xenial-8
+            - sourceline: 'deb https://apt.llvm.org/bionic/ llvm-toolchain-bionic-11 main'
+              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'
+
+    - os: linux
+      dist: bionic
+      compiler: clang++-12
+      env: UBSAN=1 TOOLSET=clang COMPILER=clang++-12 CXXSTD=11,14,17,2a UBSAN_OPTIONS=print_stacktrace=1
+      addons:
+        apt:
+          packages:
+            - clang-12
+          sources:
+            - ubuntu-toolchain-r-test
+            - sourceline: 'deb https://apt.llvm.org/bionic/ llvm-toolchain-bionic-12 main'
+              key_url: 'https://apt.llvm.org/llvm-snapshot.gpg.key'

    - os: linux
      dist: trusty
@ -268,18 +272,14 @@ matrix:
            - libc++-dev

    - os: linux
-      dist: trusty
+      dist: bionic
      compiler: clang++-libc++
-      env: UBSAN=1 TOOLSET=clang COMPILER=clang++-libc++ CXXSTD=11,14,1z UBSAN_OPTIONS=print_stacktrace=1
+      env: TOOLSET=clang COMPILER=clang++-libc++ CXXSTD=11,14,17,2a
      addons:
        apt:
          packages:
            - libc++-dev

-    - os: osx
-      compiler: clang++
-      env: TOOLSET=clang COMPILER=clang++ CXXSTD=11,14,1z
-
    - os: osx
      compiler: clang++
      env: UBSAN=1 TOOLSET=clang COMPILER=clang++ CXXSTD=11,14,1z UBSAN_OPTIONS=print_stacktrace=1
@ -288,7 +288,7 @@ matrix:
      env: CMAKE_TEST=1
      script:
        - mkdir __build__ && cd __build__
-        - cmake -DBOOST_ENABLE_CMAKE=1 -DBoost_VERBOSE=1 -DBOOST_INCLUDE_LIBRARIES=variant2 ..
+        - cmake -DBOOST_ENABLE_CMAKE=1 -DBUILD_TESTING=ON -DBoost_VERBOSE=1 -DBOOST_INCLUDE_LIBRARIES=variant2 ..
        - ctest --output-on-failure -R boost_variant2

    - os: linux
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@ -1,8 +1,9 @@
-# Copyright 2018, 2019 Peter Dimov
+# Generated by `boostdep --cmake variant2`
+# Copyright 2020, 2021 Peter Dimov
 # Distributed under the Boost Software License, Version 1.0.
-# http://www.boost.org/LICENSE_1_0.txt
+# https://www.boost.org/LICENSE_1_0.txt

-cmake_minimum_required(VERSION 3.5...3.16)
+cmake_minimum_required(VERSION 3.8...3.20)

 project(boost_variant2 VERSION "${BOOST_SUPERPROJECT_VERSION}" LANGUAGES CXX)

@ -13,11 +14,23 @@ target_include_directories(boost_variant2 INTERFACE include)

 target_link_libraries(boost_variant2
  INTERFACE
+    Boost::assert
    Boost::config
    Boost::mp11
 )

-if(BUILD_TESTING)
+if(CMAKE_VERSION VERSION_GREATER 3.18 AND CMAKE_GENERATOR MATCHES "Visual Studio")
+
+  file(GLOB_RECURSE boost_variant2_IDEFILES CONFIGURE_DEPENDS include/*.hpp)
+  source_group(TREE ${PROJECT_SOURCE_DIR}/include FILES ${boost_variant2_IDEFILES} PREFIX "Header Files")
+  list(APPEND boost_variant2_IDEFILES extra/boost_variant2.natvis)
+  target_sources(boost_variant2 PRIVATE ${boost_variant2_IDEFILES})
+
+endif()
+
+target_compile_features(boost_variant2 INTERFACE cxx_std_11)
+
+if(BUILD_TESTING AND EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/test/CMakeLists.txt")

  add_subdirectory(test)

--- a/README.md
+++ b/README.md
@ -1,21 +1,18 @@
-# variant2
+# Boost.Variant2

 This repository contains a never-valueless, strong guarantee, C++11/14/17
 implementation of [std::variant](http://en.cppreference.com/w/cpp/utility/variant).
 See [the documentation](https://www.boost.org/libs/variant2)
 for more information.

-The code requires [Boost.Mp11](https://github.com/boostorg/mp11) and
-Boost.Config.
-
-The library is part of Boost, starting from release 1.71, but the header
-`variant.hpp` will also work [standalone](https://godbolt.org/z/nVUNKX).
+The library is part of Boost, starting from release 1.71. It depends on
+Boost.Mp11, Boost.Config, and Boost.Assert.

 Supported compilers:

 * g++ 4.8 or later with `-std=c++11` or above
-* clang++ 3.5 or later with `-std=c++11` or above
-* Visual Studio 2015, 2017, 2019
+* clang++ 3.9 or later with `-std=c++11` or above
+* Visual Studio 2015 or later

-Tested on [Travis](https://travis-ci.org/boostorg/variant2/) and
+Tested on [Github Actions](https://github.com/boostorg/variant2/actions) and
 [Appveyor](https://ci.appveyor.com/project/pdimov/variant2-fkab9).
--- a/appveyor.yml
+++ b/appveyor.yml
@ -1,4 +1,4 @@
-# Copyright 2016-2020 Peter Dimov
+# Copyright 2016-2021 Peter Dimov
 # Distributed under the Boost Software License, Version 1.0.
 # (See accompanying file LICENSE_1_0.txt or copy at http://boost.org/LICENSE_1_0.txt)

@ -20,15 +20,26 @@ environment:
    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
      TOOLSET: msvc-14.1
      ADDRMD: 32,64
-      CXXSTD: 14,17
+      CXXSTD: 14,17,latest
+    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
+      TOOLSET: msvc-14.1
+      ADDRMD: 32,64
+      CXXSTD: 14,17,latest
+      CXXFLAGS: /permissive-
    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2017
      TOOLSET: clang-win
      ADDRMD: 64
-      CXXSTD: 14,17
+      CXXSTD: 14,17,latest
    - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2019
-      TOOLSET: msvc-14.2
-      ADDRMD: 32,64
-      CXXSTD: 14,17
+      TOOLSET: clang-win
+      ADDRMD: 64
+      CXXSTD: 14,17,latest
+    - 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
@ -47,4 +58,28 @@ build: off
 test_script:
  - if not "%CXXSTD%" == "" set CXXSTD=cxxstd=%CXXSTD%
  - if not "%ADDRMD%" == "" set ADDRMD=address-model=%ADDRMD%
-  - b2 -j3 libs/variant2/test toolset=%TOOLSET% %CXXSTD% %ADDRMD% variant=debug,release
+  - if not "%CXXFLAGS%" == "" set CXXFLAGS=cxxflags=%CXXFLAGS%
+  - if "%CMAKE%%CMAKE_SUBDIR%%CMAKE_INSTALL%" == ""  b2 -j3 libs/variant2/test toolset=%TOOLSET% %CXXSTD% %ADDRMD% %CXXFLAGS% variant=debug,release embed-manifest-via=linker
+
+  - if not "%CMAKE%" == ""  mkdir __build__ && cd __build__
+  - if not "%CMAKE%" == ""  cmake -DBUILD_TESTING=ON -DBOOST_INCLUDE_LIBRARIES=variant2 -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/variant2/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=variant2 -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/variant2/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
--- a/doc/variant2.adoc
+++ b/doc/variant2.adoc
@ -13,6 +13,8 @@ Peter Dimov
 :toclevels: 4
 :idprefix:
 :docinfo: private-footer
+:source-highlighter: rouge
+:source-language: c++

 :leveloffset: +1

--- a/doc/variant2/changelog.adoc
+++ b/doc/variant2/changelog.adoc
@ -1,16 +1,36 @@
 ////
-Copyright 2019, 2020 Peter Dimov
-
+Copyright 2019-2022 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
+https://www.boost.org/LICENSE_1_0.txt
 ////

 [#changelog]
 # Revision History
 :idprefix: changelog_

+## Changes in 1.83.0
+
+* Added `uses_double_storage()`.
+
+## Changes in 1.81.0
+
+* Added support for `boost::json::value_from` and `boost::json::value_to`.
+
+## Changes in 1.79.0
+
+* Added `operator<<` for `monostate`.
+
+## Changes in 1.78.0
+
+* Added `<boost/variant2.hpp>`.
+* Added `unsafe_get<I>`.
+* Added `visit_by_index`.
+* Added `operator<<`.
+
+## Changes in 1.76.0
+
+* Improved generated code for the double buffered case.
+
 ## Changes in 1.74.0

 * Added support for derived types in `visit`
--- a/doc/variant2/design.adoc
+++ b/doc/variant2/design.adoc
@ -169,6 +169,10 @@ The main differences between this implementation and `std::variant` are:
  `variant<int, float>` is provided as the member function `subset<U...>`.
  (This operation can throw if the current state of the variant cannot be
  represented.)
+* `unsafe_get`, an unchecked alternative to `get` and `get_if`, is provided
+  as an extension.
+* `visit_by_index`, a visitation function that takes a single variant and a
+  number of function objects, one per alternative, is provided as an extension.
 * The {cpp}20 additions and changes to `std::variant` have not yet been
  implemented.

--- a/doc/variant2/implementation.adoc
+++ b/doc/variant2/implementation.adoc
@ -1,10 +1,7 @@
 ////
 Copyright 2019 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
+https://www.boost.org/LICENSE_1_0.txt
 ////

 [#implementation]
@ -13,13 +10,13 @@ http://www.boost.org/LICENSE_1_0.txt

 ## Dependencies

-This implementation only depends on Boost.Config and Boost.Mp11.
+This implementation only depends on Boost.Config, Boost.Assert, and Boost.Mp11.

 ## Supported Compilers

 * GCC 4.8 or later with `-std=c++11` or above
-* Clang 3.5 or later with `-std=c++11` or above
-* Visual Studio 2015, 2017, 2019
+* Clang 3.9 or later with `-std=c++11` or above
+* Visual Studio 2015 or later

-Tested on https://travis-ci.org/boostorg/variant2/[Travis] and
+Tested on https://github.com/boostorg/variant2/actions[Github Actions] and
 https://ci.appveyor.com/project/pdimov/variant2-fkab9[Appveyor].
--- a/doc/variant2/reference.adoc
+++ b/doc/variant2/reference.adoc
@ -1,10 +1,7 @@
 ////
-Copyright 2018, 2019 Peter Dimov
-
+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
+https://www.boost.org/LICENSE_1_0.txt
 ////

 [#reference]
@ -117,6 +114,21 @@ template<class U, class... T>
  constexpr add_pointer_t<const U>
    get_if(const variant<T...>* v) noexcept;

+// unsafe_get (extension)
+
+template<size_t I, class... T>
+  constexpr variant_alternative_t<I, variant<T...>>&
+    unsafe_get(variant<T...>& v);
+template<size_t I, class... T>
+  constexpr variant_alternative_t<I, variant<T...>>&&
+    unsafe_get(variant<T...>&& v);
+template<size_t I, class... T>
+  constexpr const variant_alternative_t<I, variant<T...>>&
+    unsafe_get(const variant<T...>& v);
+template<size_t I, class... T>
+  constexpr const variant_alternative_t<I, variant<T...>>&&
+    unsafe_get(const variant<T...>&& v);
+
 // relational operators

 template<class... T>
@ -132,11 +144,21 @@ template<class... T>
 template<class... T>
  constexpr bool operator>=(const variant<T...>& v, const variant<T...>& w);

+// swap
+
+template<class... T>
+  void swap(variant<T...>& v, variant<T...>& w) noexcept( /*see below*/ );
+
 // visit

 template<class R = /*unspecified*/, class F, class... V>
  constexpr /*see below*/ visit(F&& f, V&&... v);

+// visit_by_index (extension)
+
+template<class R = /*unspecified*/, class V, class... F>
+  constexpr /*see below*/ visit_by_index(V&& v, F&&... f);
+
 // monostate

 struct monostate {};
@ -148,10 +170,15 @@ constexpr bool operator>(monostate, monostate) noexcept { return false; }
 constexpr bool operator<=(monostate, monostate) noexcept { return true; }
 constexpr bool operator>=(monostate, monostate) noexcept { return true; }

-// swap
+// stream insertion (extension)

-template<class... T>
-  void swap(variant<T...>& v, variant<T...>& w) noexcept( /*see below*/ );
+template<class Ch, class Tr, class... T>
+  std::basic_ostream<Ch, Tr>&
+    operator<<( std::basic_ostream<Ch, Tr>& os, variant<T...> const& v );
+
+template<class Ch, class Tr>
+  std::basic_ostream<Ch, Tr>&
+    operator<<( std::basic_ostream<Ch, Tr>& os, monostate const& v );

 // bad_variant_access

@ -223,6 +250,8 @@ public:
  constexpr bool valueless_by_exception() const noexcept;
  constexpr size_t index() const noexcept;

+  static constexpr bool uses_double_storage() noexcept;
+
  // swap

  void swap( variant& r ) noexcept( /*see below*/ );
@ -490,8 +519,8 @@ template<size_t I, class... A>
 +
 Requires: :: `I < sizeof...(T)`.
 Effects:  ::
-  Destroys the currently contained value, then initializes a new contained
-  value as if using the expression `Ti(std::forward<A>(a)...)`.
+  Initializes a new contained value as if using the expression
+  `Ti(std::forward<A>(a)...)`, then destroys the currently contained value.
 Ensures:  :: `index() == I`.
 Returns:  :: A reference to the new contained value.
 Throws:   ::
@ -511,8 +540,8 @@ template<size_t I, class V, class... A>
 +
 Requires: :: `I < sizeof...(T)`.
 Effects:  ::
-  Destroys the currently contained value, then initializes a new contained
-  value as if using the expression `Ti(il, std::forward<A>(a)...)`.
+  Initializes a new contained value as if using the expression
+  `Ti(il, std::forward<A>(a)...)`, then destroys the currently contained value.
 Ensures:  :: `index() == I`.
 Returns:  :: A reference to the new contained value.
 Throws:   ::
@ -543,6 +572,18 @@ constexpr size_t index() const noexcept;
 Returns:  ::
  The zero-based index of the active alternative.

+```
+static constexpr bool uses_double_storage() noexcept;
+```
+[none]
+* {blank}
+
+Returns:  ::
+  `true` if the variant uses double storage to meet the never valueless
+  guarantee because one of the alternatives is not nothrow move constructible,
+  and `false` otherwise.
+
+
 #### Swap

 ```
@ -775,6 +816,34 @@ Requires: :: The type `U` occurs exactly once in `T...`. Otherwise, the
 Effects:  :: Equivalent to: `return get_if<I>(v);` with `I` being
  the zero-based index of `U` in `T...`.

+### unsafe_get (extension)
+
+```
+template<size_t I, class... T>
+  constexpr variant_alternative_t<I, variant<T...>>&
+    unsafe_get(variant<T...>& v);
+```
+```
+template<size_t I, class... T>
+  constexpr variant_alternative_t<I, variant<T...>>&&
+    unsafe_get(variant<T...>&& v);
+```
+```
+template<size_t I, class... T>
+  constexpr const variant_alternative_t<I, variant<T...>>&
+    unsafe_get(const variant<T...>& v);
+```
+```
+template<size_t I, class... T>
+  constexpr const variant_alternative_t<I, variant<T...>>&&
+    unsafe_get(const variant<T...>&& v);
+```
+[none]
+* {blank}
+
+Requires: :: `v.index() == I`.
+Returns: :: a reference to the object stored in the variant.
+
 ### Relational Operators

 ```
@ -835,6 +904,18 @@ template<class... T>
 Returns: ::
  `w \<= v`.

+### swap
+
+```
+template<class... T>
+  void swap(variant<T...>& v, variant<T...>& w) noexcept( /*see below*/ );
+```
+[none]
+* {blank}
+
+Effects: ::
+  Equivalent to `v.swap(w)`.
+
 ### visit

 ```
@ -851,17 +932,50 @@ Remarks: :: If `R` is given explicitly, as in `visit<int>`, the return
  of `F` to the variant alternatives must have the same return type for
  this deduction to succeed.

-### swap
+### visit_by_index (extension)

 ```
-template<class... T>
-  void swap(variant<T...>& v, variant<T...>& w) noexcept( /*see below*/ );
+template<class R = /*unspecified*/, class V, class... F>
+  constexpr /*see below*/ visit_by_index(V&& v, F&&... f);
+```
+[none]
+* {blank}
+
+Requires: :: `variant_size<V>::value == sizeof...(F)`, or the program is ill-formed.
+Returns: :: `std::forward<Fi>(fi)(get<i>(std::forward<V>(v)))`, where
+  `i` is `v.index()` and `Fi` and `fi` are the `i`-th element of `F...` and `f...`
+  accordingly.
+Remarks: :: If `R` is given explicitly, as in `visit_by_index<int>`, the return
+  type is `R`. Otherwise, it's deduced from `F...` and `V`. All the applications
+  of `Fi` to the corresponding variant alternatives must have the same return type
+  for this deduction to succeed.
+
+### Stream Insertion (extension)
+```
+template<class Ch, class Tr, class... T>
+  std::basic_ostream<Ch, Tr>&
+    operator<<( std::basic_ostream<Ch, Tr>& os, variant<T...> const& v );
+```
+[none]
+* {blank}
+
+Requires: ::
+  `sizeof...(T) != 0`.
+Returns: ::
+  `os << get<I>(v)`, where `I` is `v.index()`.
+
+```
+template<class Ch, class Tr>
+  std::basic_ostream<Ch, Tr>&
+    operator<<( std::basic_ostream<Ch, Tr>& os, monostate const& v );
 ```
 [none]
 * {blank}
 +
 Effects: ::
-  Equivalent to `v.swap(w)`.
+  `os << "monostate"`.
+Returns: ::
+  `os`.

 ### bad_variant_access

@ -878,3 +992,7 @@ public:
    }
 };
 ```
+
+## <boost/variant2.hpp>
+
+This convenience header includes `<boost/variant2/variant.hpp>`.
--- a/extra/boost_variant2.natvis
+++ b/extra/boost_variant2.natvis
@ -0,0 +1,178 @@
+<?xml version="1.0" encoding="utf-8"?>
+<AutoVisualizer xmlns="http://schemas.microsoft.com/vstudio/debugger/natvis/2010">
+
+  <Type Name="boost::variant2::detail::variant_base_impl&lt;*,1,*&gt;">
+    <Intrinsic Name="index" Expression="(int)ix_ - 1"/>
+    <DisplayString Condition="index() ==  0" Optional="true">{{ index=0, value={*($T2*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() ==  1" Optional="true">{{ index=1, value={*($T3*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() ==  2" Optional="true">{{ index=2, value={*($T4*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() ==  3" Optional="true">{{ index=3, value={*($T5*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() ==  4" Optional="true">{{ index=4, value={*($T6*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() ==  5" Optional="true">{{ index=5, value={*($T7*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() ==  6" Optional="true">{{ index=6, value={*($T8*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() ==  7" Optional="true">{{ index=7, value={*($T9*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() ==  8" Optional="true">{{ index=8, value={*($T10*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() ==  9" Optional="true">{{ index=9, value={*($T11*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 10" Optional="true">{{ index=10, value={*($T12*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 11" Optional="true">{{ index=11, value={*($T13*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 12" Optional="true">{{ index=12, value={*($T14*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 13" Optional="true">{{ index=13, value={*($T15*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 14" Optional="true">{{ index=14, value={*($T16*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 15" Optional="true">{{ index=15, value={*($T17*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 16" Optional="true">{{ index=16, value={*($T18*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 17" Optional="true">{{ index=17, value={*($T19*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 18" Optional="true">{{ index=18, value={*($T20*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 19" Optional="true">{{ index=19, value={*($T21*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 20" Optional="true">{{ index=10, value={*($T22*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 21" Optional="true">{{ index=21, value={*($T23*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 22" Optional="true">{{ index=22, value={*($T24*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 23" Optional="true">{{ index=23, value={*($T25*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 24" Optional="true">{{ index=24, value={*($T26*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 25" Optional="true">{{ index=25, value={*($T27*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 26" Optional="true">{{ index=26, value={*($T28*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 27" Optional="true">{{ index=27, value={*($T29*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 28" Optional="true">{{ index=28, value={*($T30*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 29" Optional="true">{{ index=29, value={*($T31*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 30" Optional="true">{{ index=30, value={*($T32*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 31" Optional="true">{{ index=31, value={*($T33*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 32" Optional="true">{{ index=32, value={*($T34*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 33" Optional="true">{{ index=33, value={*($T35*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 34" Optional="true">{{ index=34, value={*($T36*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 35" Optional="true">{{ index=35, value={*($T37*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 36" Optional="true">{{ index=36, value={*($T38*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 37" Optional="true">{{ index=37, value={*($T39*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 38" Optional="true">{{ index=38, value={*($T40*)&amp;st_} }}</DisplayString>
+    <DisplayString Condition="index() == 39" Optional="true">{{ index=39, value={*($T41*)&amp;st_} }}</DisplayString>
+    <Expand>
+      <Item Name="index">index()</Item>
+      <Item Name="[value]" Condition="index() ==  0" Optional="true">*($T2*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() ==  1" Optional="true">*($T3*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() ==  2" Optional="true">*($T4*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() ==  3" Optional="true">*($T5*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() ==  4" Optional="true">*($T6*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() ==  5" Optional="true">*($T7*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() ==  6" Optional="true">*($T8*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() ==  7" Optional="true">*($T9*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() ==  8" Optional="true">*($T10*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() ==  9" Optional="true">*($T11*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 10" Optional="true">*($T12*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 11" Optional="true">*($T13*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 12" Optional="true">*($T14*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 13" Optional="true">*($T15*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 14" Optional="true">*($T16*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 15" Optional="true">*($T17*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 16" Optional="true">*($T18*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 17" Optional="true">*($T19*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 18" Optional="true">*($T20*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 19" Optional="true">*($T21*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 20" Optional="true">*($T22*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 21" Optional="true">*($T23*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 22" Optional="true">*($T24*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 23" Optional="true">*($T25*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 24" Optional="true">*($T26*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 25" Optional="true">*($T27*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 26" Optional="true">*($T28*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 27" Optional="true">*($T29*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 28" Optional="true">*($T30*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 29" Optional="true">*($T31*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 30" Optional="true">*($T32*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 31" Optional="true">*($T33*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 32" Optional="true">*($T34*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 33" Optional="true">*($T35*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 34" Optional="true">*($T36*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 35" Optional="true">*($T37*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 36" Optional="true">*($T38*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 37" Optional="true">*($T39*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 38" Optional="true">*($T40*)&amp;st_</Item>
+      <Item Name="[value]" Condition="index() == 39" Optional="true">*($T41*)&amp;st_</Item>
+    </Expand>
+  </Type>
+
+  <Type Name="boost::variant2::detail::variant_base_impl&lt;*,0,*&gt;">
+    <Intrinsic Name="index" Expression="(int)((ix_-2)/2)"/>
+    <DisplayString Condition="index() ==  0" Optional="true">{{ index=0, value={*($T2*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() ==  1" Optional="true">{{ index=1, value={*($T3*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() ==  2" Optional="true">{{ index=2, value={*($T4*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() ==  3" Optional="true">{{ index=3, value={*($T5*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() ==  4" Optional="true">{{ index=4, value={*($T6*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() ==  5" Optional="true">{{ index=5, value={*($T7*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() ==  6" Optional="true">{{ index=6, value={*($T8*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() ==  7" Optional="true">{{ index=7, value={*($T9*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() ==  8" Optional="true">{{ index=8, value={*($T10*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() ==  9" Optional="true">{{ index=9, value={*($T11*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 10" Optional="true">{{ index=10, value={*($T12*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 11" Optional="true">{{ index=11, value={*($T13*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 12" Optional="true">{{ index=12, value={*($T14*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 13" Optional="true">{{ index=13, value={*($T15*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 14" Optional="true">{{ index=14, value={*($T16*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 15" Optional="true">{{ index=15, value={*($T17*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 16" Optional="true">{{ index=16, value={*($T18*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 17" Optional="true">{{ index=17, value={*($T19*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 18" Optional="true">{{ index=18, value={*($T20*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 19" Optional="true">{{ index=19, value={*($T21*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 20" Optional="true">{{ index=20, value={*($T22*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 21" Optional="true">{{ index=21, value={*($T23*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 22" Optional="true">{{ index=22, value={*($T24*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 23" Optional="true">{{ index=23, value={*($T25*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 24" Optional="true">{{ index=24, value={*($T26*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 25" Optional="true">{{ index=25, value={*($T27*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 26" Optional="true">{{ index=26, value={*($T28*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 27" Optional="true">{{ index=27, value={*($T29*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 28" Optional="true">{{ index=28, value={*($T30*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 29" Optional="true">{{ index=29, value={*($T31*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 30" Optional="true">{{ index=30, value={*($T32*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 31" Optional="true">{{ index=31, value={*($T33*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 32" Optional="true">{{ index=32, value={*($T34*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 33" Optional="true">{{ index=33, value={*($T35*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 34" Optional="true">{{ index=34, value={*($T36*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 35" Optional="true">{{ index=35, value={*($T37*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 36" Optional="true">{{ index=36, value={*($T38*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 37" Optional="true">{{ index=37, value={*($T39*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 38" Optional="true">{{ index=38, value={*($T40*)&amp;st_[ix_%2]} }}</DisplayString>
+    <DisplayString Condition="index() == 39" Optional="true">{{ index=39, value={*($T41*)&amp;st_[ix_%2]} }}</DisplayString>
+    <Expand>
+      <Item Name="index">index()</Item>
+      <Item Name="[value]" Condition="index() ==  0" Optional="true">*($T2*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() ==  1" Optional="true">*($T3*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() ==  2" Optional="true">*($T4*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() ==  3" Optional="true">*($T5*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() ==  4" Optional="true">*($T6*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() ==  5" Optional="true">*($T7*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() ==  6" Optional="true">*($T8*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() ==  7" Optional="true">*($T9*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() ==  8" Optional="true">*($T10*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() ==  9" Optional="true">*($T11*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 10" Optional="true">*($T12*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 11" Optional="true">*($T13*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 12" Optional="true">*($T14*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 13" Optional="true">*($T15*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 14" Optional="true">*($T16*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 15" Optional="true">*($T17*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 16" Optional="true">*($T18*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 17" Optional="true">*($T19*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 18" Optional="true">*($T20*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 19" Optional="true">*($T21*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 20" Optional="true">*($T22*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 21" Optional="true">*($T23*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 22" Optional="true">*($T24*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 23" Optional="true">*($T25*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 24" Optional="true">*($T26*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 25" Optional="true">*($T27*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 26" Optional="true">*($T28*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 27" Optional="true">*($T29*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 28" Optional="true">*($T30*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 29" Optional="true">*($T31*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 30" Optional="true">*($T32*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 31" Optional="true">*($T33*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 32" Optional="true">*($T34*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 33" Optional="true">*($T35*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 34" Optional="true">*($T36*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 35" Optional="true">*($T37*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 36" Optional="true">*($T38*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 37" Optional="true">*($T39*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 38" Optional="true">*($T40*)&amp;st_[ix_%2]</Item>
+      <Item Name="[value]" Condition="index() == 39" Optional="true">*($T41*)&amp;st_[ix_%2]</Item>
+    </Expand>
+  </Type>
+
+</AutoVisualizer>
--- a/include/boost/variant2.hpp
+++ b/include/boost/variant2.hpp
@ -0,0 +1,10 @@
+#ifndef BOOST_VARIANT2_HPP_INCLUDED
+#define BOOST_VARIANT2_HPP_INCLUDED
+
+// Copyright 2021 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/variant2/variant.hpp>
+
+#endif // #ifndef BOOST_VARIANT2_HPP_INCLUDED
--- a/include/boost/variant2/variant.hpp
+++ b/include/boost/variant2/variant.hpp
@ -13,19 +13,19 @@
 # pragma warning( disable: 4521 4522 ) // multiple copy operators
 #endif

-#ifndef BOOST_MP11_HPP_INCLUDED
 #include <boost/mp11.hpp>
-#endif
+#include <boost/assert.hpp>
+#include <boost/assert/source_location.hpp>
 #include <boost/config.hpp>
-#include <boost/detail/workaround.hpp>
-#include <boost/cstdint.hpp>
+#include <boost/config/workaround.hpp>
 #include <cstddef>
 #include <type_traits>
 #include <exception>
-#include <cassert>
-#include <initializer_list>
 #include <utility>
-#include <functional> // std::hash
+#include <typeindex> // std::hash
+#include <iosfwd>
+#include <cstdint>
+#include <cerrno>

 //

@ -38,6 +38,8 @@ BOOST_NORETURN void throw_exception( std::exception const & e ); // user defined

 #endif

+template<class T> struct hash;
+
 namespace variant2
 {

@ -81,6 +83,8 @@ struct monostate
 {
 };

+#if !BOOST_WORKAROUND(BOOST_MSVC, < 1940)
+
 constexpr bool operator<(monostate, monostate) noexcept { return false; }
 constexpr bool operator>(monostate, monostate) noexcept { return false; }
 constexpr bool operator<=(monostate, monostate) noexcept { return true; }
@ -88,6 +92,17 @@ constexpr bool operator>=(monostate, monostate) noexcept { return true; }
 constexpr bool operator==(monostate, monostate) noexcept { return true; }
 constexpr bool operator!=(monostate, monostate) noexcept { return false; }

+#else
+
+constexpr bool operator<(monostate const&, monostate const&) noexcept { return false; }
+constexpr bool operator>(monostate const&, monostate const&) noexcept { return false; }
+constexpr bool operator<=(monostate const&, monostate const&) noexcept { return true; }
+constexpr bool operator>=(monostate const&, monostate const&) noexcept { return true; }
+constexpr bool operator==(monostate const&, monostate const&) noexcept { return true; }
+constexpr bool operator!=(monostate const&, monostate const&) noexcept { return false; }
+
+#endif
+
 // variant forward declaration

 template<class... T> class variant;
@ -351,37 +366,50 @@ template<std::size_t I, class... T> constexpr variant_alternative_t<I, variant<T
 #endif
 }

-// detail::unsafe_get (for visit)
+// unsafe_get

-namespace detail
-{
+#if !defined(BOOST_NO_CXX14_CONSTEXPR)
+# define BOOST_VARIANT2_CX14_ASSERT(expr) BOOST_ASSERT(expr);
+#else
+# define BOOST_VARIANT2_CX14_ASSERT(expr)
+#endif

 template<std::size_t I, class... T> constexpr variant_alternative_t<I, variant<T...>>& unsafe_get(variant<T...>& v)
 {
    static_assert( I < sizeof...(T), "Index out of bounds" );
+
+    BOOST_VARIANT2_CX14_ASSERT( v.index() == I )
+
    return v._get_impl( mp11::mp_size_t<I>() );
 }

 template<std::size_t I, class... T> constexpr variant_alternative_t<I, variant<T...>>&& unsafe_get(variant<T...>&& v)
 {
    static_assert( I < sizeof...(T), "Index out of bounds" );
+
+    BOOST_VARIANT2_CX14_ASSERT( v.index() == I )
+
    return std::move( v._get_impl( mp11::mp_size_t<I>() ) );
 }

 template<std::size_t I, class... T> constexpr variant_alternative_t<I, variant<T...>> const& unsafe_get(variant<T...> const& v)
 {
    static_assert( I < sizeof...(T), "Index out of bounds" );
+
+    BOOST_VARIANT2_CX14_ASSERT( v.index() == I )
+
    return v._get_impl( mp11::mp_size_t<I>() );
 }

 template<std::size_t I, class... T> constexpr variant_alternative_t<I, variant<T...>> const&& unsafe_get(variant<T...> const&& v)
 {
    static_assert( I < sizeof...(T), "Index out of bounds" );
+
+    BOOST_VARIANT2_CX14_ASSERT( v.index() == I )
+
    return std::move( v._get_impl( mp11::mp_size_t<I>() ) );
 }

-} // namespace detail
-
 // get (type)

 template<class U, class... T> constexpr U& get(variant<T...>& v)
@ -520,11 +548,11 @@ template<class T1, class... T> union variant_storage_impl<mp11::mp_false, T1, T.
    T1 first_;
    variant_storage<T...> rest_;

-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<0>, A&&... a ): first_( std::forward<A>(a)... )
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<0>, A&&... a ): first_( std::forward<A>(a)... )
    {
    }

-    template<std::size_t I, class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<I>, A&&... a ): rest_( mp11::mp_size_t<I-1>(), std::forward<A>(a)... )
+    template<std::size_t I, class... A> constexpr variant_storage_impl( mp11::mp_size_t<I>, A&&... a ): rest_( mp11::mp_size_t<I-1>(), std::forward<A>(a)... )
    {
    }

@ -564,18 +592,18 @@ template<class T0, class T1, class T2, class T3, class T4, class T5, class T6, c

    variant_storage<T...> rest_;

-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<0>, A&&... a ): t0_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<1>, A&&... a ): t1_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<2>, A&&... a ): t2_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<3>, A&&... a ): t3_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<4>, A&&... a ): t4_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<5>, A&&... a ): t5_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<6>, A&&... a ): t6_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<7>, A&&... a ): t7_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<8>, A&&... a ): t8_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<9>, A&&... a ): t9_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<0>, A&&... a ): t0_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<1>, A&&... a ): t1_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<2>, A&&... a ): t2_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<3>, A&&... a ): t3_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<4>, A&&... a ): t4_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<5>, A&&... a ): t5_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<6>, A&&... a ): t6_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<7>, A&&... a ): t7_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<8>, A&&... a ): t8_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<9>, A&&... a ): t9_( std::forward<A>(a)... ) {}

-    template<std::size_t I, class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<I>, A&&... a ): rest_( mp11::mp_size_t<I-10>(), std::forward<A>(a)... ) {}
+    template<std::size_t I, class... A> constexpr variant_storage_impl( mp11::mp_size_t<I>, A&&... a ): rest_( mp11::mp_size_t<I-10>(), std::forward<A>(a)... ) {}

    ~variant_storage_impl()
    {
@ -637,11 +665,11 @@ template<class T1, class... T> union variant_storage_impl<mp11::mp_true, T1, T..
    T1 first_;
    variant_storage<T...> rest_;

-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<0>, A&&... a ): first_( std::forward<A>(a)... )
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<0>, A&&... a ): first_( std::forward<A>(a)... )
    {
    }

-    template<std::size_t I, class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<I>, A&&... a ): rest_( mp11::mp_size_t<I-1>(), std::forward<A>(a)... )
+    template<std::size_t I, class... A> constexpr variant_storage_impl( mp11::mp_size_t<I>, A&&... a ): rest_( mp11::mp_size_t<I-1>(), std::forward<A>(a)... )
    {
    }

@ -657,7 +685,20 @@ template<class T1, class... T> union variant_storage_impl<mp11::mp_true, T1, T..

    template<std::size_t I, class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_true, mp11::mp_size_t<I>, A&&... a )
    {
+#if defined(BOOST_GCC) && (__GNUC__ >= 7)
+# pragma GCC diagnostic push
+// False positive in at least GCC 7 and GCC 10 ASAN triggered by monostate (via result<void>)
+# pragma GCC diagnostic ignored "-Wmaybe-uninitialized"
+#if __GNUC__ >= 12
+// False positive in at least GCC 12 and GCC 13 ASAN and -Og triggered by monostate (via result<void>)
+# pragma GCC diagnostic ignored "-Wuninitialized"
+#endif
+#endif
        *this = variant_storage_impl( mp11::mp_size_t<I>(), std::forward<A>(a)... );
+
+#if defined(BOOST_GCC) && (__GNUC__ >= 7)
+# pragma GCC diagnostic pop
+#endif
    }

    template<std::size_t I, class... A> BOOST_CXX14_CONSTEXPR void emplace( mp11::mp_size_t<I>, A&&... a )
@ -687,18 +728,18 @@ template<class T0, class T1, class T2, class T3, class T4, class T5, class T6, c

    variant_storage<T...> rest_;

-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<0>, A&&... a ): t0_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<1>, A&&... a ): t1_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<2>, A&&... a ): t2_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<3>, A&&... a ): t3_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<4>, A&&... a ): t4_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<5>, A&&... a ): t5_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<6>, A&&... a ): t6_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<7>, A&&... a ): t7_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<8>, A&&... a ): t8_( std::forward<A>(a)... ) {}
-    template<class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<9>, A&&... a ): t9_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<0>, A&&... a ): t0_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<1>, A&&... a ): t1_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<2>, A&&... a ): t2_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<3>, A&&... a ): t3_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<4>, A&&... a ): t4_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<5>, A&&... a ): t5_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<6>, A&&... a ): t6_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<7>, A&&... a ): t7_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<8>, A&&... a ): t8_( std::forward<A>(a)... ) {}
+    template<class... A> constexpr variant_storage_impl( mp11::mp_size_t<9>, A&&... a ): t9_( std::forward<A>(a)... ) {}

-    template<std::size_t I, class... A> constexpr explicit variant_storage_impl( mp11::mp_size_t<I>, A&&... a ): rest_( mp11::mp_size_t<I-10>(), std::forward<A>(a)... ) {}
+    template<std::size_t I, class... A> constexpr variant_storage_impl( mp11::mp_size_t<I>, A&&... a ): rest_( mp11::mp_size_t<I-10>(), std::forward<A>(a)... ) {}

    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<0>, A&&... a ) { ::new( &t0_ ) T0( std::forward<A>(a)... ); }
    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<1>, A&&... a ) { ::new( &t1_ ) T1( std::forward<A>(a)... ); }
@ -814,21 +855,21 @@ struct none {};
 // trivially destructible, single buffered
 template<class... T> struct variant_base_impl<true, true, T...>
 {
-    int ix_;
-    variant_storage<none, T...> st1_;
+    variant_storage<none, T...> st_;
+    unsigned ix_;

-    constexpr variant_base_impl(): ix_( 0 ), st1_( mp11::mp_size_t<0>() )
+    constexpr variant_base_impl(): st_( mp11::mp_size_t<0>() ), ix_( 0 )
    {
    }

-    template<class I, class... A> constexpr explicit variant_base_impl( I, A&&... a ): ix_( I::value + 1 ), st1_( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... )
+    template<class I, class... A> constexpr explicit variant_base_impl( I, A&&... a ): st_( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... ), ix_( I::value + 1 )
    {
    }

    // requires: ix_ == 0
    template<class I, class... A> void _replace( I, A&&... a )
    {
-        ::new( &st1_ ) variant_storage<none, T...>( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... );
+        ::new( &st_ ) variant_storage<none, T...>( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... );
        ix_ = I::value + 1;
    }

@ -841,24 +882,25 @@ template<class... T> struct variant_base_impl<true, true, T...>
    {
        size_t const J = I+1;

-        assert( ix_ == J );
+        BOOST_ASSERT( ix_ == J );

-        return st1_.get( mp11::mp_size_t<J>() );
+        return st_.get( mp11::mp_size_t<J>() );
    }

    template<std::size_t I> constexpr mp11::mp_at_c<variant<T...>, I> const& _get_impl( mp11::mp_size_t<I> ) const noexcept
    {
        // size_t const J = I+1;
-        // assert( ix_ == I+1 );

-        return st1_.get( mp11::mp_size_t<I+1>() );
+        BOOST_VARIANT2_CX14_ASSERT( ix_ == I+1 )
+
+        return st_.get( mp11::mp_size_t<I+1>() );
    }

    template<std::size_t J, class U, class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_true, A&&... a )
    {
        static_assert( std::is_nothrow_constructible<U, A&&...>::value, "Logic error: U must be nothrow constructible from A&&..." );

-        st1_.emplace( mp11::mp_size_t<J>(), std::forward<A>(a)... );
+        st_.emplace( mp11::mp_size_t<J>(), std::forward<A>(a)... );
        ix_ = J;
    }

@ -868,7 +910,7 @@ template<class... T> struct variant_base_impl<true, true, T...>

        U tmp( std::forward<A>(a)... );

-        st1_.emplace( mp11::mp_size_t<J>(), std::move(tmp) );
+        st_.emplace( mp11::mp_size_t<J>(), std::move(tmp) );
        ix_ = J;
    }

@ -879,89 +921,94 @@ template<class... T> struct variant_base_impl<true, true, T...>

        this->emplace_impl<J, U>( std::is_nothrow_constructible<U, A&&...>(), std::forward<A>(a)... );
    }
+
+    static constexpr bool uses_double_storage() noexcept
+    {
+        return false;
+    }
 };

 // trivially destructible, double buffered
 template<class... T> struct variant_base_impl<true, false, T...>
 {
-    int ix_;
-    variant_storage<none, T...> st1_;
-    variant_storage<none, T...> st2_;
+    variant_storage<none, T...> st_[ 2 ];
+    unsigned ix_;

-    constexpr variant_base_impl(): ix_( 0 ), st1_( mp11::mp_size_t<0>() ), st2_( mp11::mp_size_t<0>() )
+    constexpr variant_base_impl(): st_{ { mp11::mp_size_t<0>() }, { mp11::mp_size_t<0>() } }, ix_( 0 )
    {
    }

-    template<class I, class... A> constexpr explicit variant_base_impl( I, A&&... a ): ix_( I::value + 1 ), st1_( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... ), st2_( mp11::mp_size_t<0>() )
+    template<class I, class... A> constexpr explicit variant_base_impl( I, A&&... a ): st_{ { mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... }, { mp11::mp_size_t<0>() } }, ix_( ( I::value + 1 ) * 2 )
    {
    }

    // requires: ix_ == 0
    template<class I, class... A> void _replace( I, A&&... a )
    {
-        ::new( &st1_ ) variant_storage<none, T...>( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... );
-        ix_ = I::value + 1;
+        ::new( &st_[ 0 ] ) variant_storage<none, T...>( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... );
+        ix_ = ( I::value + 1 ) * 2;
    }

    constexpr std::size_t index() const noexcept
    {
-        return ix_ >= 0? ix_ - 1: -ix_ - 1;
+        return ix_ / 2 - 1;
    }

    template<std::size_t I> BOOST_CXX14_CONSTEXPR mp11::mp_at_c<variant<T...>, I>& _get_impl( mp11::mp_size_t<I> ) noexcept
    {
+        BOOST_ASSERT( index() == I );
+
        size_t const J = I+1;

-        assert( ix_ == J || -ix_ == J );
-
        constexpr mp11::mp_size_t<J> j{};
-        return ix_ >= 0? st1_.get( j ): st2_.get( j );
+        return st_[ ix_ & 1 ].get( j );
    }

    template<std::size_t I> constexpr mp11::mp_at_c<variant<T...>, I> const& _get_impl( mp11::mp_size_t<I> ) const noexcept
    {
+        BOOST_VARIANT2_CX14_ASSERT( index() == I )
+
        // size_t const J = I+1;
-        // assert( ix_ == J || -ix_ == J );
        // constexpr mp_size_t<J> j{};

-        return ix_ >= 0? st1_.get( mp11::mp_size_t<I+1>() ): st2_.get( mp11::mp_size_t<I+1>() );
+        return st_[ ix_ & 1 ].get( mp11::mp_size_t<I+1>() );
    }

    template<std::size_t I, class... A> BOOST_CXX14_CONSTEXPR void emplace( A&&... a )
    {
        size_t const J = I+1;

-        if( ix_ >= 0 )
-        {
-            st2_.emplace( mp11::mp_size_t<J>(), std::forward<A>(a)... );
-            ix_ = -static_cast<int>( J );
-        }
-        else
-        {
-            st1_.emplace( mp11::mp_size_t<J>(), std::forward<A>(a)... );
-            ix_ = J;
-        }
+        unsigned i2 = 1 - ( ix_ & 1 );
+
+        st_[ i2 ].emplace( mp11::mp_size_t<J>(), std::forward<A>(a)... );
+
+        ix_ = J * 2 + i2;
+    }
+
+    static constexpr bool uses_double_storage() noexcept
+    {
+        return true;
    }
 };

 // not trivially destructible, single buffered
 template<class... T> struct variant_base_impl<false, true, T...>
 {
-    int ix_;
-    variant_storage<none, T...> st1_;
+    variant_storage<none, T...> st_;
+    unsigned ix_;

-    constexpr variant_base_impl(): ix_( 0 ), st1_( mp11::mp_size_t<0>() )
+    constexpr variant_base_impl(): st_( mp11::mp_size_t<0>() ), ix_( 0 )
    {
    }

-    template<class I, class... A> constexpr explicit variant_base_impl( I, A&&... a ): ix_( I::value + 1 ), st1_( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... )
+    template<class I, class... A> constexpr explicit variant_base_impl( I, A&&... a ): st_( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... ), ix_( I::value + 1 )
    {
    }

    // requires: ix_ == 0
    template<class I, class... A> void _replace( I, A&&... a )
    {
-        ::new( &st1_ ) variant_storage<none, T...>( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... );
+        ::new( &st_ ) variant_storage<none, T...>( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... );
        ix_ = I::value + 1;
    }

@ -977,7 +1024,7 @@ template<class... T> struct variant_base_impl<false, true, T...>
        template<class I> void operator()( I ) const noexcept
        {
            using U = mp11::mp_at<mp11::mp_list<none, T...>, I>;
-            this_->st1_.get( I() ).~U();
+            this_->st_.get( I() ).~U();
        }
    };

@ -1003,17 +1050,18 @@ template<class... T> struct variant_base_impl<false, true, T...>
    {
        size_t const J = I+1;

-        assert( ix_ == J );
+        BOOST_ASSERT( ix_ == J );

-        return st1_.get( mp11::mp_size_t<J>() );
+        return st_.get( mp11::mp_size_t<J>() );
    }

    template<std::size_t I> constexpr mp11::mp_at_c<variant<T...>, I> const& _get_impl( mp11::mp_size_t<I> ) const noexcept
    {
        // size_t const J = I+1;
-        // assert( ix_ == J );

-        return st1_.get( mp11::mp_size_t<I+1>() );
+        BOOST_VARIANT2_CX14_ASSERT( ix_ == I+1 )
+
+        return st_.get( mp11::mp_size_t<I+1>() );
    }

    template<std::size_t I, class... A> void emplace( A&&... a )
@ -1028,31 +1076,74 @@ template<class... T> struct variant_base_impl<false, true, T...>

        _destroy();

-        st1_.emplace( mp11::mp_size_t<J>(), std::move(tmp) );
+        st_.emplace( mp11::mp_size_t<J>(), std::move(tmp) );
        ix_ = J;
    }
+
+    static constexpr bool uses_double_storage() noexcept
+    {
+        return false;
+    }
 };

 // not trivially destructible, double buffered
 template<class... T> struct variant_base_impl<false, false, T...>
 {
-    int ix_;
-    variant_storage<none, T...> st1_;
-    variant_storage<none, T...> st2_;
+#if defined(__GNUC__) && __GNUC__ < 11 && !defined(__clang__) && !defined(__INTEL_COMPILER)

-    constexpr variant_base_impl(): ix_( 0 ), st1_( mp11::mp_size_t<0>() ), st2_( mp11::mp_size_t<0>() )
+    // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63707 :-(
+
+    variant_storage<none, T...> st1_, st2_;
+    unsigned ix_;
+
+    constexpr variant_base_impl(): st1_( mp11::mp_size_t<0>() ), st2_( mp11::mp_size_t<0>() ), ix_( 0 )
    {
    }

-    template<class I, class... A> constexpr explicit variant_base_impl( I, A&&... a ): ix_( I::value + 1 ), st1_( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... ), st2_( mp11::mp_size_t<0>() )
+    template<class I, class... A> constexpr explicit variant_base_impl( I, A&&... a ): st1_( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... ), st2_( mp11::mp_size_t<0>() ), ix_( ( I::value + 1 ) * 2 )
    {
    }

+    BOOST_CXX14_CONSTEXPR variant_storage<none, T...>& storage( unsigned i2 ) noexcept
+    {
+        return i2 == 0? st1_: st2_;
+    }
+
+    constexpr variant_storage<none, T...> const& storage( unsigned i2 ) const noexcept
+    {
+        return i2 == 0? st1_: st2_;
+    }
+
+#else
+
+    variant_storage<none, T...> st_[ 2 ];
+    unsigned ix_;
+
+    constexpr variant_base_impl(): st_{ { mp11::mp_size_t<0>() }, { mp11::mp_size_t<0>() } }, ix_( 0 )
+    {
+    }
+
+    template<class I, class... A> constexpr explicit variant_base_impl( I, A&&... a ): st_{ { mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... }, { mp11::mp_size_t<0>() } }, ix_( ( I::value + 1 ) * 2 )
+    {
+    }
+
+    BOOST_CXX14_CONSTEXPR variant_storage<none, T...>& storage( unsigned i2 ) noexcept
+    {
+        return st_[ i2 ];
+    }
+
+    constexpr variant_storage<none, T...> const& storage( unsigned i2 ) const noexcept
+    {
+        return st_[ i2 ];
+    }
+
+#endif
+
    // requires: ix_ == 0
    template<class I, class... A> void _replace( I, A&&... a )
    {
-        ::new( &st1_ ) variant_storage<none, T...>( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... );
-        ix_ = I::value + 1;
+        ::new( &storage( 0 ) ) variant_storage<none, T...>( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... );
+        ix_ = ( I::value + 1 ) * 2;
    }

    //[&]( auto I ){
@ -1063,35 +1154,18 @@ template<class... T> struct variant_base_impl<false, false, T...>
    struct _destroy_L1
    {
        variant_base_impl * this_;
+        unsigned i2_;

        template<class I> void operator()( I ) const noexcept
        {
            using U = mp11::mp_at<mp11::mp_list<none, T...>, I>;
-            this_->st1_.get( I() ).~U();
-        }
-    };
-
-    struct _destroy_L2
-    {
-        variant_base_impl * this_;
-
-        template<class I> void operator()( I ) const noexcept
-        {
-            using U = mp11::mp_at<mp11::mp_list<none, T...>, I>;
-            this_->st2_.get( I() ).~U();
+            this_->storage( i2_ ).get( I() ).~U();
        }
    };

    void _destroy() noexcept
    {
-        if( ix_ > 0 )
-        {
-            mp11::mp_with_index<1 + sizeof...(T)>( ix_, _destroy_L1{ this } );
-        }
-        else if( ix_ < 0 )
-        {
-            mp11::mp_with_index<1 + sizeof...(T)>( -ix_, _destroy_L2{ this } );
-        }
+        mp11::mp_with_index<1 + sizeof...(T)>( ix_ / 2, _destroy_L1{ this, ix_ & 1 } );
    }

    ~variant_base_impl() noexcept
@ -1101,46 +1175,44 @@ template<class... T> struct variant_base_impl<false, false, T...>

    constexpr std::size_t index() const noexcept
    {
-        return ix_ >= 0? ix_ - 1: -ix_ - 1;
+        return ix_ / 2 - 1;
    }

    template<std::size_t I> BOOST_CXX14_CONSTEXPR mp11::mp_at_c<variant<T...>, I>& _get_impl( mp11::mp_size_t<I> ) noexcept
    {
+        BOOST_ASSERT( index() == I );
+
        size_t const J = I+1;

-        assert( ix_ == J || -ix_ == J );
-
        constexpr mp11::mp_size_t<J> j{};
-        return ix_ >= 0? st1_.get( j ): st2_.get( j );
+        return storage( ix_ & 1 ).get( j );
    }

    template<std::size_t I> constexpr mp11::mp_at_c<variant<T...>, I> const& _get_impl( mp11::mp_size_t<I> ) const noexcept
    {
+        BOOST_VARIANT2_CX14_ASSERT( index() == I )
+
        // size_t const J = I+1;
-        // assert( ix_ == J || -ix_ == J );
        // constexpr mp_size_t<J> j{};

-        return ix_ >= 0? st1_.get( mp11::mp_size_t<I+1>() ): st2_.get( mp11::mp_size_t<I+1>() );
+        return storage( ix_ & 1 ).get( mp11::mp_size_t<I+1>() );
    }

    template<std::size_t I, class... A> void emplace( A&&... a )
    {
        size_t const J = I+1;

-        if( ix_ >= 0 )
-        {
-            st2_.emplace( mp11::mp_size_t<J>(), std::forward<A>(a)... );
-            _destroy();
+        unsigned i2 = 1 - ( ix_ & 1 );

-            ix_ = -static_cast<int>( J );
-        }
-        else
-        {
-            st1_.emplace( mp11::mp_size_t<J>(), std::forward<A>(a)... );
-            _destroy();
+        storage( i2 ).emplace( mp11::mp_size_t<J>(), std::forward<A>(a)... );
+        _destroy();

-            ix_ = J;
-        }
+        ix_ = J * 2 + i2;
+    }
+
+    static constexpr bool uses_double_storage() noexcept
+    {
+        return true;
    }
 };

@ -1561,8 +1633,18 @@ public:

    template<class U,
        class Ud = typename std::decay<U>::type,
-        class E1 = typename std::enable_if< !std::is_same<Ud, variant>::value && !detail::is_in_place_index<Ud>::value && !detail::is_in_place_type<Ud>::value >::type,
+        class E1 = typename std::enable_if< !std::is_same<Ud, variant>::value && !std::is_base_of<variant, Ud>::value && !detail::is_in_place_index<Ud>::value && !detail::is_in_place_type<Ud>::value >::type,
+
+#if BOOST_WORKAROUND(BOOST_MSVC, < 1950)
+
+        class V = mp11::mp_apply_q< mp11::mp_bind_front<detail::resolve_overload_type, U&&>, variant >,
+
+#else
+
        class V = detail::resolve_overload_type<U&&, T...>,
+
+#endif
+
        class E2 = typename std::enable_if<std::is_constructible<V, U&&>::value>::type
        >
    constexpr variant( U&& u )
@ -1652,6 +1734,8 @@ public:

    using variant_base::index;

+    using variant_base::uses_double_storage;
+
    // swap

 private:
@ -2085,7 +2169,7 @@ template<class R, class F, class V1, class V2> struct visit_L2
    template<class I> auto operator()( I ) const -> Vret<R, F, V1, V2>
    {
        auto f2 = bind_front( std::forward<F>(f), unsafe_get<I::value>( std::forward<V1>(v1) ) );
-		return visit<R>( f2, std::forward<V2>(v2) );
+        return visit<R>( f2, std::forward<V2>(v2) );
    }
 };

@ -2153,7 +2237,7 @@ template<class R = detail::deduced, class F, class V1, class V2, class... V> con
 {
    return mp11::mp_with_index<detail::variant_base_size<V1>>( v1.index(), [&]( auto I ){

-        auto f2 = [&]( auto&&... a ){ return std::forward<F>(f)( detail::unsafe_get<I.value>( std::forward<V1>(v1) ), std::forward<decltype(a)>(a)... ); };
+        auto f2 = [&]( auto&&... a ){ return std::forward<F>(f)( unsafe_get<I.value>( std::forward<V1>(v1) ), std::forward<decltype(a)>(a)... ); };
        return visit<R>( f2, std::forward<V2>(v2), std::forward<V>(v)... );

    });
@ -2170,36 +2254,133 @@ void swap( variant<T...> & v, variant<T...> & w )
    v.swap( w );
 }

+// visit_by_index
+
+namespace detail
+{
+
+template<class R, class V, class... F> using Vret2 = mp11::mp_eval_if_not< std::is_same<R, deduced>, R, front_if_same, mp11::mp_transform<mp11::mp_invoke_q, mp11::mp_list<Qret<F>...>, apply_cv_ref<V>> >;
+
+template<class R, class V, class... F> struct visit_by_index_L
+{
+    V&& v;
+    std::tuple<F&&...> tp;
+
+    template<class I> constexpr detail::Vret2<R, V, F...> operator()( I ) const
+    {
+        return std::get<I::value>( std::move(tp) )( unsafe_get<I::value>( std::forward<V>(v) ) );
+    }
+};
+
+} // namespace detail
+
+template<class R = detail::deduced, class V, class... F> constexpr auto visit_by_index( V&& v, F&&... f ) -> detail::Vret2<R, V, F...>
+{
+    static_assert( variant_size<V>::value == sizeof...(F), "Incorrect number of function objects" );
+
+    return mp11::mp_with_index<variant_size<V>::value>( v.index(),
+        detail::visit_by_index_L<R, V, F...>{ std::forward<V>(v), std::tuple<F&&...>( std::forward<F>(f)... ) } );
+}
+
+// output streaming
+
+namespace detail
+{
+
+template<class Ch, class Tr, class... T> struct ostream_insert_L
+{
+    std::basic_ostream<Ch, Tr>& os;
+    variant<T...> const& v;
+
+    template<class I> std::basic_ostream<Ch, Tr>& operator()( I ) const
+    {
+        return os << unsafe_get<I::value>( v );
+    }
+};
+
+template<class Os, class T, class E = void> struct is_output_streamable: std::false_type
+{
+};
+
+template<class Os, class T> struct is_output_streamable<Os, T, decltype( std::declval<Os&>() << std::declval<T const&>(), (void)0 )>: std::true_type
+{
+};
+
+} // namespace detail
+
+template<class Ch, class Tr>
+std::basic_ostream<Ch, Tr>& operator<<( std::basic_ostream<Ch, Tr>& os, monostate const& )
+{
+    os << "monostate";
+    return os;
+}
+
+template<class Ch, class Tr, class T1, class... T,
+    class E = typename std::enable_if< mp11::mp_all< detail::is_output_streamable<std::basic_ostream<Ch, Tr>, T>... >::value >::type >
+std::basic_ostream<Ch, Tr>& operator<<( std::basic_ostream<Ch, Tr>& os, variant<T1, T...> const& v )
+{
+    return mp11::mp_with_index<1 + sizeof...(T)>( v.index(),
+        detail::ostream_insert_L<Ch, Tr, T1, T...>{ os, v } );
+}
+
 // hashing support

 namespace detail
 {

-template<class V> struct hash_value_L
+inline std::size_t hash_value_impl_( mp11::mp_true, std::size_t index, std::size_t value )
+{
+    unsigned long long hv = 0xCBF29CE484222325ull;
+    unsigned long long const prime = 0x100000001B3ull;
+
+    hv ^= index;
+    hv *= prime;
+
+    hv ^= value;
+    hv *= prime;
+
+    return static_cast<std::size_t>( hv );
+}
+
+inline std::size_t hash_value_impl_( mp11::mp_false, std::size_t index, std::size_t value )
+{
+    std::size_t hv = 0x811C9DC5;
+    std::size_t const prime = 0x01000193;
+
+    hv ^= index;
+    hv *= prime;
+
+    hv ^= value;
+    hv *= prime;
+
+    return hv;
+}
+
+inline std::size_t hash_value_impl( std::size_t index, std::size_t value )
+{
+    return hash_value_impl_( mp11::mp_bool< (SIZE_MAX > UINT32_MAX) >(), index, value );
+}
+
+template<template<class> class H, class V> struct hash_value_L
 {
    V const & v;

    template<class I> std::size_t operator()( I ) const
    {
-        boost::ulong_long_type hv = ( boost::ulong_long_type( 0xCBF29CE4 ) << 32 ) + 0x84222325;
-        boost::ulong_long_type const prime = ( boost::ulong_long_type( 0x00000100 ) << 32 ) + 0x000001B3;
-
-        // index
-
-        hv ^= I::value;
-        hv *= prime;
-
-        // value
-
        auto const & t = unsafe_get<I::value>( v );

-        hv ^= std::hash<remove_cv_ref_t<decltype(t)>>()( t );
-        hv *= prime;
+        std::size_t index = I::value;
+        std::size_t value = H<remove_cv_ref_t<decltype(t)>>()( t );

-        return static_cast<std::size_t>( hv );
+        return hash_value_impl( index, value );
    }
 };

+template<class... T> std::size_t hash_value_std( variant<T...> const & v )
+{
+    return mp11::mp_with_index<sizeof...(T)>( v.index(), detail::hash_value_L< std::hash, variant<T...> >{ v } );
+}
+
 } // namespace detail

 inline std::size_t hash_value( monostate const & )
@ -2209,7 +2390,7 @@ inline std::size_t hash_value( monostate const & )

 template<class... T> std::size_t hash_value( variant<T...> const & v )
 {
-    return mp11::mp_with_index<sizeof...(T)>( v.index(), detail::hash_value_L< variant<T...> >{ v } );
+    return mp11::mp_with_index<sizeof...(T)>( v.index(), detail::hash_value_L< boost::hash, variant<T...> >{ v } );
 }

 namespace detail
@ -2230,7 +2411,7 @@ template<class V> struct std_hash_impl<V, true>
 {
    std::size_t operator()( V const & v ) const
    {
-        return hash_value( v );
+        return detail::hash_value_std( v );
    }
 };

@ -2256,6 +2437,111 @@ template<> struct hash< ::boost::variant2::monostate >

 } // namespace std

+// JSON support
+
+namespace boost
+{
+namespace json
+{
+
+class value;
+
+struct value_from_tag;
+
+template<class T>
+void value_from( T&& t, value& jv );
+
+template<class T>
+struct try_value_to_tag;
+
+template<class T1, class T2>
+struct result_for;
+
+template<class T>
+typename result_for<T, value>::type
+try_value_to( value const & jv );
+
+template<class T>
+typename result_for<T, value>::type
+result_from_errno( int e, boost::source_location const* loc ) noexcept;
+
+template<class T> struct is_null_like;
+
+template<> struct is_null_like<variant2::monostate>: std::true_type {};
+
+} // namespace json
+
+namespace variant2
+{
+
+namespace detail
+{
+
+struct tag_invoke_L1
+{
+    boost::json::value& v;
+
+#if defined(BOOST_MSVC) && BOOST_MSVC / 10 == 191
+    // msvc-14.1 with /permissive- needs this
+    explicit tag_invoke_L1( boost::json::value& v_ ): v( v_ ) {}
+#endif
+
+    template<class T> void operator()( T const& t ) const
+    {
+        boost::json::value_from( t, v );
+    }
+};
+
+} // namespace detail
+
+template<class... T>
+    void tag_invoke( boost::json::value_from_tag const&, boost::json::value& v, variant<T...> const & w )
+{
+    visit( detail::tag_invoke_L1{ v }, w );
+}
+
+namespace detail
+{
+
+template<class V> struct tag_invoke_L2
+{
+    boost::json::value const& v;
+    typename boost::json::result_for<V, boost::json::value>::type& r;
+
+    template<class I> void operator()( I /*i*/ ) const
+    {
+        if( !r )
+        {
+            using Ti = mp11::mp_at_c<V, I::value>;
+            auto r2 = boost::json::try_value_to<Ti>( v );
+
+            if( r2 )
+            {
+                r.emplace( in_place_index_t<I::value>{}, std::move( *r2 ) );
+            }
+        }
+    }
+};
+
+} // namespace detail
+
+template<class... T>
+    typename boost::json::result_for<variant<T...>, boost::json::value>::type
+    tag_invoke( boost::json::try_value_to_tag<variant<T...>> const&, boost::json::value const& v )
+{
+    static constexpr boost::source_location loc = BOOST_CURRENT_LOCATION;
+    auto r = boost::json::result_from_errno< variant<T...> >( EINVAL, &loc );
+
+    mp11::mp_for_each<mp11::mp_iota_c<sizeof...(T)>>( detail::tag_invoke_L2< variant<T...> >{ v, r } );
+
+    return r;
+}
+
+} // namespace variant2
+} // namespace boost
+
+#undef BOOST_VARIANT2_CX14_ASSERT
+
 #if defined(_MSC_VER) && _MSC_VER < 1910
 # pragma warning( pop )
 #endif
--- a/meta/libraries.json
+++ b/meta/libraries.json
@ -5,10 +5,11 @@
        "Peter Dimov"
    ],
    "maintainers": [
-        "Peter Dimov <pdimov -at- pdimov.com>"
+        "Peter Dimov <pdimov -at- gmail.com>"
    ],
    "description": "A never-valueless, strong guarantee implementation of std::variant.",
    "category": [
        "Containers", "Data"
-    ]
+    ],
+    "cxxstd": "11"
 }
--- a/test/Jamfile
+++ b/test/Jamfile
@ -16,8 +16,6 @@ project

  : requirements

-    [ requires cxx11_variadic_templates cxx11_template_aliases cxx11_decltype cxx11_constexpr ]
-
    <toolset>msvc:<warnings-as-errors>on
    <toolset>gcc:<warnings-as-errors>on
    <toolset>clang:<warnings-as-errors>on
@ -115,4 +113,23 @@ run variant_visit_derived.cpp ;

 run variant_many_types.cpp ;

-run variant_visit_r.cpp ;
+run variant_visit_r.cpp : : :
+    <toolset>gcc,<target-os>windows:<variant>release
+    <toolset>gcc,<target-os>cygwin:<variant>release
+    ;
+
+compile variant_derived_construct.cpp ;
+
+run variant_visit_by_index.cpp ;
+
+run variant_ostream_insert.cpp ;
+run is_output_streamable.cpp ;
+
+local JSON = <library>/boost//json/<warnings>off "<toolset>msvc-14.0:<build>no" "<toolset>msvc-14.2:<cxxflags>-wd5104" "<undefined-sanitizer>norecover:<link>static" ;
+
+run variant_json_value_from.cpp : : : $(JSON) ;
+run variant_json_value_to.cpp : : : $(JSON) ;
+
+compile variant_uses_double_storage.cpp ;
+
+run variant_derived_construct2.cpp ;
--- a/test/cmake_subdir_test/CMakeLists.txt
+++ b/test/cmake_subdir_test/CMakeLists.txt
@ -7,6 +7,8 @@ cmake_minimum_required(VERSION 3.5...3.16)
 project(cmake_subdir_test LANGUAGES CXX)

 add_subdirectory(../.. boostorg/variant2)
+
+add_subdirectory(../../../assert boostorg/assert)
 add_subdirectory(../../../config boostorg/config)
 add_subdirectory(../../../mp11 boostorg/mp11)

--- a/test/is_output_streamable.cpp
+++ b/test/is_output_streamable.cpp
@ -0,0 +1,41 @@
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/variant2/variant.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <ostream>
+#include <string>
+
+struct X
+{
+};
+
+struct Y
+{
+};
+
+std::ostream& operator<<( std::ostream& os, Y const& /*y*/ )
+{
+    os << "Y()";
+    return os;
+}
+
+int main()
+{
+    BOOST_TEST_TRAIT_TRUE((boost::variant2::detail::is_output_streamable<std::ostream, int>));
+    BOOST_TEST_TRAIT_TRUE((boost::variant2::detail::is_output_streamable<std::ostream, float>));
+    BOOST_TEST_TRAIT_TRUE((boost::variant2::detail::is_output_streamable<std::ostream, std::string>));
+    BOOST_TEST_TRAIT_FALSE((boost::variant2::detail::is_output_streamable<std::ostream, void>));
+    BOOST_TEST_TRAIT_FALSE((boost::variant2::detail::is_output_streamable<std::ostream, X>));
+    BOOST_TEST_TRAIT_TRUE((boost::variant2::detail::is_output_streamable<std::ostream, Y>));
+
+    BOOST_TEST_TRAIT_TRUE((boost::variant2::detail::is_output_streamable<std::ostream, boost::variant2::monostate>));
+
+    BOOST_TEST_TRAIT_TRUE((boost::variant2::detail::is_output_streamable<std::ostream, boost::variant2::variant<int, float, std::string>>));
+    BOOST_TEST_TRAIT_FALSE((boost::variant2::detail::is_output_streamable<std::ostream, boost::variant2::variant<int, float, X>>));
+    BOOST_TEST_TRAIT_TRUE((boost::variant2::detail::is_output_streamable<std::ostream, boost::variant2::variant<int, float, Y>>));
+    BOOST_TEST_TRAIT_TRUE((boost::variant2::detail::is_output_streamable<std::ostream, boost::variant2::variant<boost::variant2::monostate, int, float>>));
+
+    return boost::report_errors();
+}
--- a/test/quick.cpp
+++ b/test/quick.cpp
@ -1,10 +1,8 @@
-
 // Copyright 2019 Peter Dimov.
-//
 // Distributed under the Boost Software License, Version 1.0.
-// http://www.boost.org/LICENSE_1_0.txt
+// https://www.boost.org/LICENSE_1_0.txt

-#include <boost/variant2/variant.hpp>
+#include <boost/variant2.hpp>

 using namespace boost::variant2;

--- a/test/variant_derived_construct.cpp
+++ b/test/variant_derived_construct.cpp
@ -0,0 +1,33 @@
+// Copyright 2021 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/variant2/variant.hpp>
+
+using namespace boost::variant2;
+
+template<class... T> class X: variant<T...>
+{
+    using base = variant<T...>;
+    using base::base;
+};
+
+struct Y
+{
+    Y( Y const& rhs ) = default;
+
+    template<class T> Y( T const& t )
+    {
+        t.bar();
+    }
+};
+
+int main()
+{
+    using W = X<int, double, Y>;
+
+    W a( 1 );
+    W b( a );
+
+    (void)b;
+}
--- a/test/variant_derived_construct2.cpp
+++ b/test/variant_derived_construct2.cpp
@ -0,0 +1,60 @@
+// Copyright 2024 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/variant2/variant.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+struct expr: boost::variant2::variant<bool, int, double>
+{
+    using variant::variant;
+};
+
+int main()
+{
+    using boost::variant2::get;
+
+    {
+        expr v{ true };
+
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v), true );
+    }
+
+    {
+        expr v{ 2 };
+
+        BOOST_TEST_EQ( v.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v), 2 );
+    }
+
+    {
+        expr v{ 3.0 };
+
+        BOOST_TEST_EQ( v.index(), 2 );
+        BOOST_TEST_EQ( get<2>(v), 3.0 );
+    }
+
+    {
+        expr v( true );
+
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v), true );
+    }
+
+    {
+        expr v( 2 );
+
+        BOOST_TEST_EQ( v.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v), 2 );
+    }
+
+    {
+        expr v( 3.0 );
+
+        BOOST_TEST_EQ( v.index(), 2 );
+        BOOST_TEST_EQ( get<2>(v), 3.0 );
+    }
+
+    return boost::report_errors();
+}
--- a/test/variant_emplace_index.cpp
+++ b/test/variant_emplace_index.cpp
@ -57,6 +57,60 @@ STATIC_ASSERT( !std::is_nothrow_move_constructible<X2>::value );
 STATIC_ASSERT( !std::is_nothrow_copy_assignable<X2>::value );
 STATIC_ASSERT( !std::is_nothrow_move_assignable<X2>::value );

+struct Y1
+{
+    int v = 1;
+
+    Y1() = default;
+    Y1(Y1 const&) = delete;
+    Y1(Y1&&) = delete;
+};
+
+STATIC_ASSERT( !std::is_copy_constructible<Y1>::value );
+STATIC_ASSERT( !std::is_move_constructible<Y1>::value );
+
+struct Y2
+{
+    int v = 2;
+
+    Y2() = default;
+    Y2(Y2 const&) = delete;
+    Y2(Y2&&) = delete;
+};
+
+STATIC_ASSERT( !std::is_copy_constructible<Y2>::value );
+STATIC_ASSERT( !std::is_move_constructible<Y2>::value );
+
+struct Z1
+{
+    static int instances;
+
+    int v = 1;
+
+    Z1() { ++instances; }
+    ~Z1() { --instances; }
+
+    Z1(Z1 const&) = delete;
+    Z1(Z1&&) = delete;
+};
+
+int Z1::instances = 0;
+
+struct Z2
+{
+    static int instances;
+
+    int v = 2;
+
+    Z2() { ++instances; }
+    ~Z2() { --instances; }
+
+    Z2(Z2 const&) = delete;
+    Z2(Z2&&) = delete;
+};
+
+int Z2::instances = 0;
+
 int main()
 {
    {
@ -177,5 +231,96 @@ int main()
        BOOST_TEST_EQ( get<0>(v).v, 4 );
    }

+    {
+        variant<Y1, Y2> v;
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v).v, 1 );
+
+        v.emplace<0>();
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v).v, 1 );
+
+        v.emplace<1>();
+        BOOST_TEST_EQ( v.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v).v, 2 );
+
+        v.emplace<1>();
+        BOOST_TEST_EQ( v.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v).v, 2 );
+
+        v.emplace<0>();
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v).v, 1 );
+    }
+
+    {
+        variant<Z1, Z2> v;
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v).v, 1 );
+        BOOST_TEST_EQ( Z1::instances, 1 );
+        BOOST_TEST_EQ( Z2::instances, 0 );
+
+        v.emplace<0>();
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v).v, 1 );
+        BOOST_TEST_EQ( Z1::instances, 1 );
+        BOOST_TEST_EQ( Z2::instances, 0 );
+
+        v.emplace<1>();
+        BOOST_TEST_EQ( v.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v).v, 2 );
+        BOOST_TEST_EQ( Z1::instances, 0 );
+        BOOST_TEST_EQ( Z2::instances, 1 );
+
+        v.emplace<1>();
+        BOOST_TEST_EQ( v.index(), 1 );
+        BOOST_TEST_EQ( get<1>(v).v, 2 );
+        BOOST_TEST_EQ( Z1::instances, 0 );
+        BOOST_TEST_EQ( Z2::instances, 1 );
+
+        v.emplace<0>();
+        BOOST_TEST_EQ( v.index(), 0 );
+        BOOST_TEST_EQ( get<0>(v).v, 1 );
+        BOOST_TEST_EQ( Z1::instances, 1 );
+        BOOST_TEST_EQ( Z2::instances, 0 );
+    }
+
+    BOOST_TEST_EQ( Z1::instances, 0 );
+    BOOST_TEST_EQ( Z2::instances, 0 );
+
+    {
+        variant<monostate, monostate> v;
+        BOOST_TEST_EQ( v.index(), 0 );
+
+        v.emplace<0>();
+        BOOST_TEST_EQ( v.index(), 0 );
+
+        v.emplace<1>();
+        BOOST_TEST_EQ( v.index(), 1 );
+
+        v.emplace<1>();
+        BOOST_TEST_EQ( v.index(), 1 );
+
+        v.emplace<0>();
+        BOOST_TEST_EQ( v.index(), 0 );
+    }
+
+    {
+        variant<monostate, int> v;
+        BOOST_TEST_EQ( v.index(), 0 );
+
+        v.emplace<0>();
+        BOOST_TEST_EQ( v.index(), 0 );
+
+        v.emplace<1>();
+        BOOST_TEST_EQ( v.index(), 1 );
+
+        v.emplace<1>();
+        BOOST_TEST_EQ( v.index(), 1 );
+
+        v.emplace<0>();
+        BOOST_TEST_EQ( v.index(), 0 );
+    }
+
    return boost::report_errors();
 }
--- a/test/variant_eq_ne.cpp
+++ b/test/variant_eq_ne.cpp
@ -88,5 +88,12 @@ int main()
        BOOST_TEST_NOT( v1 != v2 );
    }

+    {
+        variant<monostate> v1, v2;
+
+        BOOST_TEST( v1 == v2 );
+        BOOST_TEST_NOT( v1 != v2 );
+    }
+
    return boost::report_errors();
 }
--- a/test/variant_eq_ne_cx.cpp
+++ b/test/variant_eq_ne_cx.cpp
@ -93,6 +93,13 @@ int main()
        STATIC_ASSERT( !(v1 == v2) );
        STATIC_ASSERT( !(v1 != v2) );
    }
+
+    {
+        constexpr variant<monostate> v1, v2;
+
+        STATIC_ASSERT( v1 == v2 );
+        STATIC_ASSERT( !(v1 != v2) );
+    }
 }

 #endif
--- a/test/variant_get_by_index_cx.cpp
+++ b/test/variant_get_by_index_cx.cpp
@ -58,7 +58,7 @@ int main()
    {
        constexpr variant<int, float> v( 3.14f );

-        STATIC_ASSERT( get<1>(v) == 3.14f );
+        STATIC_ASSERT( get<1>(v) == (float)3.14f ); // see FLT_EVAL_METHOD

        STATIC_ASSERT_IF( get_if<0>(&v) == nullptr );
        STATIC_ASSERT_IF( get_if<1>(&v) == &get<1>(v) );
@ -87,7 +87,7 @@ int main()
    {
        constexpr variant<int, int, float> v( 3.14f );

-        STATIC_ASSERT( get<2>(v) == 3.14f );
+        STATIC_ASSERT( get<2>(v) == (float)3.14f );

        STATIC_ASSERT_IF( get_if<0>(&v) == nullptr );
        STATIC_ASSERT_IF( get_if<1>(&v) == nullptr );
--- a/test/variant_get_by_type_cx.cpp
+++ b/test/variant_get_by_type_cx.cpp
@ -58,7 +58,7 @@ int main()
    {
        constexpr variant<int, float> v( 3.14f );

-        STATIC_ASSERT( get<float>(v) == 3.14f );
+        STATIC_ASSERT( get<float>(v) == (float)3.14f ); // see FLT_EVAL_METHOD

        STATIC_ASSERT_IF( get_if<int>(&v) == nullptr );
        STATIC_ASSERT_IF( get_if<float>(&v) == &get<float>(v) );
@ -83,7 +83,7 @@ int main()
    {
        constexpr variant<int, int, float> v( 3.14f );

-        STATIC_ASSERT( get<float>(v) == 3.14f );
+        STATIC_ASSERT( get<float>(v) == (float)3.14f );

        STATIC_ASSERT_IF( get_if<float>(&v) == &get<float>(v) );
    }
--- a/test/variant_hash.cpp
+++ b/test/variant_hash.cpp
@ -12,6 +12,7 @@
 #include <boost/core/lightweight_test_trait.hpp>
 #include <boost/container_hash/hash.hpp>
 #include <boost/config/workaround.hpp>
+#include <vector>

 using namespace boost::variant2;

@ -47,7 +48,17 @@ template<template<class...> class Hash, class T> void test2()
    BOOST_TEST_NE( h2, h3 );
 }

-struct X {};
+struct X
+{
+    int m = 0;
+};
+
+std::size_t hash_value( X const& x )
+{
+    return boost::hash<int>()( x.m );
+}
+
+struct Y {}; // no hash support

 int main()
 {
@ -57,6 +68,8 @@ int main()
    test<boost::hash, monostate, monostate, monostate>();
    test<boost::hash, int, int, float>();

+    test<boost::hash, monostate, X, std::vector<X>>();
+
    test2<std::hash, int>();
    test2<std::hash, float>();

@ -65,7 +78,7 @@ int main()

 #if !BOOST_WORKAROUND(BOOST_MSVC, < 1910) && ( !defined(_LIBCPP_STD_VER) || _LIBCPP_STD_VER > 11 )

-    BOOST_TEST_TRAIT_FALSE(( detail::is_hash_enabled<X> ));
+    BOOST_TEST_TRAIT_FALSE(( detail::is_hash_enabled<Y> ));

 #endif

--- a/test/variant_in_place_index_construct_cx.cpp
+++ b/test/variant_in_place_index_construct_cx.cpp
@ -68,7 +68,7 @@ int main()
        constexpr variant<int, float> v( in_place_index_t<1>{}, 3.14f );

        STATIC_ASSERT( v.index() == 1 );
-        STATIC_ASSERT( get<1>(v) == 3.14f );
+        STATIC_ASSERT( get<1>(v) == (float)3.14f ); // see FLT_EVAL_METHOD
    }

    {
@ -89,14 +89,14 @@ int main()
        constexpr variant<int, int, float, float, X, X> v( in_place_index_t<2>{}, 3.14f );

        STATIC_ASSERT( v.index() == 2 );
-        STATIC_ASSERT( get<2>(v) == 3.14f );
+        STATIC_ASSERT( get<2>(v) == (float)3.14f );
    }

    {
        constexpr variant<int, int, float, float, X, X> v( in_place_index_t<3>{}, 3.14f );

        STATIC_ASSERT( v.index() == 3 );
-        STATIC_ASSERT( get<3>(v) == 3.14f );
+        STATIC_ASSERT( get<3>(v) == (float)3.14f );
    }

    {
@ -105,9 +105,9 @@ int main()
        STATIC_ASSERT( v.index() == 4 );
    }

-#if BOOST_WORKAROUND(BOOST_GCC, >= 100000 && BOOST_GCC < 100200)
+#if BOOST_WORKAROUND(BOOST_GCC, >= 100000 && BOOST_GCC < 120000)

-    // no idea why this fails on g++ 10
+    // no idea why this fails on g++ 10/11

 #else

--- a/test/variant_in_place_type_construct_cx.cpp
+++ b/test/variant_in_place_type_construct_cx.cpp
@ -80,7 +80,7 @@ int main()
        constexpr variant<int, float> v( in_place_type_t<float>{}, 3.14f );

        STATIC_ASSERT( v.index() == 1 );
-        STATIC_ASSERT( get<1>(v) == 3.14f );
+        STATIC_ASSERT( get<1>(v) == (float)3.14f ); // see FLT_EVAL_METHOD

        STATIC_ASSERT( holds_alternative<float>(v) );
    }
@ -89,7 +89,7 @@ int main()
        constexpr variant<int, int, float, X> v( in_place_type_t<float>{}, 3.14f );

        STATIC_ASSERT( v.index() == 2 );
-        STATIC_ASSERT( get<2>(v) == 3.14f );
+        STATIC_ASSERT( get<2>(v) == (float)3.14f );

        STATIC_ASSERT( holds_alternative<float>(v) );
    }
@ -102,9 +102,9 @@ int main()
        STATIC_ASSERT( holds_alternative<X>(v) );
    }

-#if BOOST_WORKAROUND(BOOST_GCC, >= 100000 && BOOST_GCC < 100200)
+#if BOOST_WORKAROUND(BOOST_GCC, >= 100000 && BOOST_GCC < 120000)

-    // no idea why this fails on g++ 10
+    // no idea why this fails on g++ 10/11

 #else

--- a/test/variant_json_value_from.cpp
+++ b/test/variant_json_value_from.cpp
@ -0,0 +1,41 @@
+// Copyright 2022 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/variant2/variant.hpp>
+#include <boost/json/value_from.hpp>
+#include <boost/json/serialize.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <string>
+
+using namespace boost::variant2;
+namespace json = boost::json;
+
+int main()
+{
+    {
+        monostate m;
+        json::value w = json::value_from( m );
+        BOOST_TEST_EQ( w, json::value( nullptr ) );
+    }
+
+    {
+        variant<monostate, int, std::string> v;
+        json::value w = json::value_from( v );
+        BOOST_TEST_EQ( w, json::value( nullptr ) );
+    }
+
+    {
+        variant<monostate, int, std::string> v( 17 );
+        json::value w = json::value_from( v );
+        BOOST_TEST_EQ( w, json::value( 17 ) );
+    }
+
+    {
+        variant<monostate, int, std::string> v( "test" );
+        json::value w = json::value_from( v );
+        BOOST_TEST_EQ( w, json::value( "test" ) );
+    }
+
+    return boost::report_errors();
+}
--- a/test/variant_json_value_to.cpp
+++ b/test/variant_json_value_to.cpp
@ -0,0 +1,42 @@
+// Copyright 2022 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/variant2/variant.hpp>
+#include <boost/json/value_to.hpp>
+#include <boost/json/serialize.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+using namespace boost::variant2;
+namespace json = boost::json;
+
+int main()
+{
+    {
+        json::value v;
+        auto r = json::try_value_to<monostate>( v );
+        BOOST_TEST( r.has_value() );
+    }
+
+    using V = variant<monostate, int, std::string>;
+
+    {
+        json::value v;
+        auto r = json::try_value_to<V>( v );
+        BOOST_TEST( r.has_value() ) && BOOST_TEST_EQ( *r, V() );
+    }
+
+    {
+        json::value v( 12 );
+        auto r = json::try_value_to<V>( v );
+        BOOST_TEST( r.has_value() ) && BOOST_TEST_EQ( *r, V(12) );
+    }
+
+    {
+        json::value v( "test" );
+        auto r = json::try_value_to<V>( v );
+        BOOST_TEST( r.has_value() ) && BOOST_TEST_EQ( *r, V("test") );
+    }
+
+    return boost::report_errors();
+}
--- a/test/variant_lt_gt.cpp
+++ b/test/variant_lt_gt.cpp
@ -81,5 +81,14 @@ int main()
        BOOST_TEST_NOT( v1 >= v2 );
    }

+    {
+        variant<monostate> v1, v2;
+
+        BOOST_TEST_NOT( v1 < v2 );
+        BOOST_TEST_NOT( v1 > v2 );
+        BOOST_TEST( v1 <= v2 );
+        BOOST_TEST( v1 >= v2 );
+    }
+
    return boost::report_errors();
 }
--- a/test/variant_lt_gt_cx.cpp
+++ b/test/variant_lt_gt_cx.cpp
@ -86,6 +86,15 @@ int main()
        STATIC_ASSERT( !(v1 <= v2) );
        STATIC_ASSERT( !(v1 >= v2) );
    }
+
+    {
+        constexpr variant<monostate> v1, v2;
+
+        STATIC_ASSERT( !(v1 < v2) );
+        STATIC_ASSERT( !(v1 > v2) );
+        STATIC_ASSERT( v1 <= v2 );
+        STATIC_ASSERT( v1 >= v2 );
+    }
 }

 #endif
--- a/test/variant_ostream_insert.cpp
+++ b/test/variant_ostream_insert.cpp
@ -0,0 +1,43 @@
+// Copyright 2021 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/variant2/variant.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <sstream>
+#include <string>
+
+using namespace boost::variant2;
+
+template<class T> std::string to_string( T const& t )
+{
+    std::ostringstream os;
+
+    os << t;
+
+    return os.str();
+}
+
+int main()
+{
+    {
+        BOOST_TEST_EQ( to_string( monostate() ), "monostate" );
+    }
+
+    {
+        variant<monostate, int, float, std::string> v;
+
+        BOOST_TEST_EQ( to_string( v ), to_string( monostate() ) );
+
+        v = 1;
+        BOOST_TEST_EQ( to_string( v ), to_string( 1 ) );
+
+        v = 3.14f;
+        BOOST_TEST_EQ( to_string( v ), to_string( 3.14f ) );
+
+        v = "test";
+        BOOST_TEST_EQ( to_string( v ), to_string( "test" ) );
+    }
+
+    return boost::report_errors();
+}
--- a/test/variant_uses_double_storage.cpp
+++ b/test/variant_uses_double_storage.cpp
@ -0,0 +1,50 @@
+// Copyright 2023 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/variant2/variant.hpp>
+#include <type_traits>
+
+using namespace boost::variant2;
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+struct X1
+{
+};
+
+STATIC_ASSERT( std::is_nothrow_move_constructible<X1>::value );
+STATIC_ASSERT( std::is_trivially_destructible<X1>::value );
+
+struct X2
+{
+    ~X2() {}
+};
+
+STATIC_ASSERT( std::is_nothrow_move_constructible<X2>::value );
+STATIC_ASSERT( !std::is_trivially_destructible<X2>::value );
+
+struct X3
+{
+    X3( X3&& ) {}
+};
+
+STATIC_ASSERT( !std::is_nothrow_move_constructible<X3>::value );
+STATIC_ASSERT( std::is_trivially_destructible<X3>::value );
+
+struct X4
+{
+    ~X4() {}
+    X4( X4&& ) {}
+};
+
+STATIC_ASSERT( !std::is_nothrow_move_constructible<X4>::value );
+STATIC_ASSERT( !std::is_trivially_destructible<X4>::value );
+
+//
+
+STATIC_ASSERT( !variant<int, float>::uses_double_storage() );
+STATIC_ASSERT( !variant<int, float, X1>::uses_double_storage() );
+STATIC_ASSERT( !variant<int, float, X2>::uses_double_storage() );
+STATIC_ASSERT( variant<int, float, X3>::uses_double_storage() );
+STATIC_ASSERT( variant<int, float, X4>::uses_double_storage() );
--- a/test/variant_value_construct_cx.cpp
+++ b/test/variant_value_construct_cx.cpp
@ -82,7 +82,7 @@ int main()

        STATIC_ASSERT( v.index() == 1 );
        STATIC_ASSERT( holds_alternative<float>(v) );
-        STATIC_ASSERT( get<1>(v) == 3.14f );
+        STATIC_ASSERT( get<1>(v) == (float)3.14f ); // see FLT_EVAL_METHOD
    }

    {
@ -97,7 +97,7 @@ int main()

        STATIC_ASSERT( v.index() == 2 );
        STATIC_ASSERT( holds_alternative<float>(v) );
-        STATIC_ASSERT( get<2>(v) == 3.14f );
+        STATIC_ASSERT( get<2>(v) == (float)3.14f );
    }

    {
--- a/test/variant_visit_by_index.cpp
+++ b/test/variant_visit_by_index.cpp
@ -0,0 +1,126 @@
+// Copyright 2017, 2021 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/variant2/variant.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/core/lightweight_test_trait.hpp>
+#include <boost/mp11.hpp>
+#include <boost/config.hpp>
+
+using namespace boost::variant2;
+using boost::mp11::mp_int;
+
+struct X
+{
+};
+
+struct F1
+{
+    int operator()( X& ) const { return 1; }
+    int operator()( X const& ) const { return 2; }
+    int operator()( X&& ) const { return 3; }
+    int operator()( X const&& ) const { return 4; }
+};
+
+struct F2
+{
+    mp_int<1> operator()( X& ) const { return {}; }
+    mp_int<2> operator()( X const& ) const { return {}; }
+    mp_int<3> operator()( X&& ) const { return {}; }
+    mp_int<4> operator()( X const&& ) const { return {}; }
+};
+
+int main()
+{
+    {
+        variant<int, int, float> v;
+
+        visit_by_index( v,
+            []( int& x ){ BOOST_TEST_EQ( x, 0 ); },
+            []( int&   ){ BOOST_ERROR( "incorrect alternative" ); },
+            []( float& ){ BOOST_ERROR( "incorrect alternative" ); } );
+    }
+
+    {
+        variant<int const, int, float const> v( in_place_index_t<0>(), 1 );
+
+        visit_by_index( v,
+            []( int const& x ){ BOOST_TEST_EQ( x, 1 ); },
+            []( int&         ){ BOOST_ERROR( "incorrect alternative" ); },
+            []( float const& ){ BOOST_ERROR( "incorrect alternative" ); } );
+    }
+
+    {
+        variant<int, int, float> const v( in_place_index_t<1>(), 2 );
+
+        visit_by_index( v,
+            []( int const&   ){ BOOST_ERROR( "incorrect alternative" ); },
+            []( int const& x ){ BOOST_TEST_EQ( x, 2 ); },
+            []( float const& ){ BOOST_ERROR( "incorrect alternative" ); } );
+    }
+
+    {
+        variant<int const, int, float const> const v( 3.14f );
+
+        visit_by_index( v,
+            []( int const&     ){ BOOST_ERROR( "incorrect alternative" ); },
+            []( int const&     ){ BOOST_ERROR( "incorrect alternative" ); },
+            []( float const& x ){ BOOST_TEST_EQ( x, 3.14f ); } );
+    }
+
+    {
+        variant<int, float> const v( 7 );
+
+        auto r = visit_by_index( v,
+            []( int const& x   ) -> double { return x; },
+            []( float const& x ) -> double { return x; } );
+
+        BOOST_TEST_TRAIT_SAME( decltype(r), double );
+        BOOST_TEST_EQ( r, 7.0 );
+    }
+
+    {
+        variant<int, float> const v( 2.0f );
+
+        auto r = visit_by_index( v,
+            []( int const& x   ) { return x + 0.0; },
+            []( float const& x ) { return x + 0.0; } );
+
+        BOOST_TEST_TRAIT_SAME( decltype(r), double );
+        BOOST_TEST_EQ( r, 2.0 );
+    }
+
+    {
+        variant<int, float, double> const v( 3.0 );
+
+        auto r = visit_by_index<double>( v,
+            []( int const& x    ) { return x; },
+            []( float const& x  ) { return x; },
+            []( double const& x ) { return x; } );
+
+        BOOST_TEST_TRAIT_SAME( decltype(r), double );
+        BOOST_TEST_EQ( r, 3.0 );
+    }
+
+    {
+        variant<X> v;
+        variant<X> const cv;
+
+        F1 f1;
+
+        BOOST_TEST_EQ( visit_by_index( v, f1 ), 1 );
+        BOOST_TEST_EQ( visit_by_index( cv, f1 ), 2 );
+        BOOST_TEST_EQ( visit_by_index( std::move( v ), f1 ), 3 );
+        BOOST_TEST_EQ( visit_by_index( std::move( cv ), f1 ), 4 );
+
+        F2 f2;
+
+        BOOST_TEST_EQ( visit_by_index<int>( v, f2 ), 1 );
+        BOOST_TEST_EQ( visit_by_index<int>( cv, f2 ), 2 );
+        BOOST_TEST_EQ( visit_by_index<int>( std::move( v ), f2 ), 3 );
+        BOOST_TEST_EQ( visit_by_index<int>( std::move( cv ), f2 ), 4 );
+    }
+
+    return boost::report_errors();
+}
--- a/test/variant_visit_derived.cpp
+++ b/test/variant_visit_derived.cpp
@ -1,4 +1,3 @@
-
 // Copyright 2017, 2020 Peter Dimov.
 // Distributed under the Boost Software License, Version 1.0.
 // https://www.boost.org/LICENSE_1_0.txt
@ -15,7 +14,7 @@

 struct X: boost::variant2::variant<int, float>
 {
-#if BOOST_WORKAROUND( BOOST_MSVC, < 1930 )
+#if BOOST_WORKAROUND( BOOST_MSVC, < 1940 )

    template<class T> explicit X( T&& t ): variant( std::forward<T>( t ) ) {};

--- a/test/variant_visit_r.cpp
+++ b/test/variant_visit_r.cpp
@ -61,18 +61,18 @@ int main()
    }

    {
-        variant<int, float> const v( 3.14f );
+        variant<int, float> const v( 3.125f );

        BOOST_TEST_EQ( visit<int>( F1(), v ), 3 );
-        BOOST_TEST_EQ( visit<float>( F1(), v ), 3.14f );
+        BOOST_TEST_EQ( visit<float>( F1(), v ), 3.125f );
    }

    {
        variant<int, float> v1( 1 );
-        variant<int, float> const v2( 3.14f );
+        variant<int, float> const v2( 3.125f );

        BOOST_TEST_EQ( visit<int>( F2(), v1, v2 ), 4 );
-        BOOST_TEST_EQ( visit<float>( F2(), v1, v2 ), 1 + 3.14f );
+        BOOST_TEST_EQ( visit<float>( F2(), v1, v2 ), 1 + 3.125f );
    }

    {
Author	SHA1	Message	Date
Peter Dimov	f9bdafd3ca	Remove C++11 requirements from test/Jamfile	2024-05-18 03:18:56 +03:00
Peter Dimov	38293da18e	Update .drone.jsonnet	2024-05-18 02:43:52 +03:00
Peter Dimov	65ab0f8cef	Update ci.yml	2024-05-17 22:04:55 +03:00
Peter Dimov	78796d0e7d	Increase workaround to < 1950, because VS2022 has reached _MSC_VER=1940. Refs #43 .	2024-05-17 21:44:21 +03:00
Peter Dimov	ff36c3aa1f	Merge pull request #42 from K-ballo/more-natvis Improve natvis	2024-03-25 02:22:20 +02:00
Peter Dimov	f0acc9326e	Work around MSVC failures in variant_derived_construct2. Refs #43 .	2024-03-24 19:16:09 +02:00
Peter Dimov	a936eae01b	Add test/variant_derived_construct2. Refs #43 .	2024-03-24 18:41:49 +02:00
Agustin Berge	77234b514c	Improve natvis: - extend support from 10 to 40 alternatives, - split single-buffer vs double-buffer definitions, - adjust display string to follow MS definition for std::variant	2024-03-23 16:04:54 -03:00
Peter Dimov	c125b32938	Add msvc-14.3 /permissive- to Drone	2024-02-08 20:58:45 +02:00
Peter Dimov	3298078c8b	Update .drone.jsonnet	2024-01-11 22:05:28 +02:00
Peter Dimov	a38839febc	Update ci.yml	2024-01-11 21:20:40 +02:00
Peter Dimov	c3071b7d0b	Merge pull request #40 from Lastique/patch-1 Add missing dots in visit_by_index docs	2024-01-11 21:03:37 +02:00
Andrey Semashev	9cf32980a9	Add missing dots in visit_by_index docs	2024-01-11 20:18:06 +03:00
Peter Dimov	9e4234bfd5	Merge pull request #39 from 13steinj/develop Suppress -Wuninitialized in emplace_impl	2023-10-24 12:42:10 +03:00
Jonathan Stein	55f1332ce0	Suppress -Wuninitialized in emplace_impl Closes #38	2023-10-23 15:46:15 -05:00
Peter Dimov	db12c36b89	Remove unnecessary includes	2023-10-11 18:28:11 +03:00
Peter Dimov	a5cb0582d5	Make tag_invoke_L2 more msvc-14.0-friendly	2023-09-03 18:28:49 +03:00
Peter Dimov	e2546b70ca	Document uses_double_storage(). Refs #37 .	2023-06-29 18:32:58 +03:00
Peter Dimov	362224a009	Update ci.yml	2023-06-29 16:44:47 +03:00
Peter Dimov	2c590716ab	Use the exact 3.125f in variant_visit_r.cpp	2023-06-29 12:05:55 +03:00
Peter Dimov	82b98fb757	Cast 3.14f to float because FLT_EVAL_METHOD (see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108742 ) for discussion	2023-06-29 10:46:54 +03:00
Peter Dimov	30afb9e183	Update test/Jamfile to fix Drone issues	2023-06-29 09:54:49 +03:00
Peter Dimov	129e27ce09	Update Drone files	2023-06-29 09:33:44 +03:00
Peter Dimov	26595285d3	Add variant<>::uses_double_storage(). Refs #37 .	2023-06-28 22:14:56 +03:00
Peter Dimov	95a8c5ffec	Update .drone.jsonnet	2023-01-23 03:53:25 +02:00
Peter Dimov	ec2819a05e	Update CMakeLists.txt	2023-01-13 00:56:45 +02:00
Peter Dimov	fcf9746a2d	Merge branch 'develop' of https://github.com/vinniefalco/boost-variant2 into feature/pr-36	2023-01-13 00:55:17 +02:00
Peter Dimov	a74ebd34dc	Update appveyor.yml	2023-01-12 21:12:17 +02:00
Peter Dimov	1b34c20685	Update appveyor.yml	2023-01-12 18:38:10 +02:00
Peter Dimov	604d3700ad	Add CMake tests to Appveyor	2023-01-12 10:49:41 +02:00
Peter Dimov	4d1fd43d72	Update supported compilers in documentation and README	2022-10-27 21:25:57 +03:00
Peter Dimov	376925a209	Work around msvc-14.1 /permissive- failure	2022-10-24 15:47:09 +03:00
Peter Dimov	bcb8796225	Add /permissive- jobs to Drone and Appveyor	2022-10-24 15:27:05 +03:00
Peter Dimov	a948b85c74	Update revision history	2022-10-18 17:38:59 +03:00
Peter Dimov	32862d6db7	Add missing std::move	2022-10-18 16:02:33 +03:00
Peter Dimov	423d350ff1	Remove unneeded forward declarations	2022-10-18 16:01:31 +03:00
Peter Dimov	aad1f86fae	Reflect the change in is_null_like	2022-10-18 16:00:14 +03:00
Peter Dimov	1f8c4a1900	Replace polymorphic lambdas with function objects for C++11	2022-10-18 06:29:57 +03:00
Peter Dimov	67a12199e6	Add JSON support (refs #28 )	2022-10-18 06:08:18 +03:00
Peter Dimov	457147d1b0	Suppress -Wmaybe-uninitialized in emplace_impl	2022-10-18 03:20:36 +03:00
Peter Dimov	4a5f3dc498	Add variant<monostate, T>::emplace tests to fish out -Wmaybe-uninitialized warnings	2022-10-18 02:56:15 +03:00
Peter Dimov	6fe1c69bc8	Add Drone support	2022-10-18 02:16:59 +03:00
Peter Dimov	78a974429a	Update ci.yml	2022-10-15 19:39:32 +03:00
Vinnie Falco	4c5f254b9c	add boost_variant2.natvis and interface source files	2022-08-19 12:13:08 -07:00
Peter Dimov	c633a953de	Change macos-10.15 to macos-11 in ci.yml	2022-08-15 19:26:35 +03:00
Peter Dimov	8ee7c5aad0	Update ci.yml	2022-07-14 14:47:06 +03:00
Peter Dimov	d34658f4c8	Document operator<< for monostate	2022-01-31 19:19:49 +02:00
Peter Dimov	5e2bce1baa	Add operator<< for monostate	2022-01-31 17:55:26 +02:00
Peter Dimov	573ef77382	Move unsigned ix_ after the elements to avoid need to adjust rdi (closes #30 )	2021-12-09 21:28:35 +02:00
Peter Dimov	f6cad272d4	Add msvc-14.0 to GHA	2021-12-09 19:59:01 +02:00
Peter Dimov	3fc7540733	Only define operator<< when all contained types are streamable (refs #31 )	2021-12-09 18:39:03 +02:00
Peter Dimov	e4b4b3f02b	Extend msvc-14.2 workaround to 14.3	2021-10-29 02:18:23 +03:00
Peter Dimov	44d38c4111	Enable syntax highlighting	2021-10-28 23:23:13 +03:00
Peter Dimov	1ebfb3b689	Add msvc-14.3 to ci.yml	2021-10-28 23:22:20 +03:00
Peter Dimov	8af1fbde8e	Update cmake_subdir_test/CMakeLists.txt	2021-09-21 14:52:38 +03:00
Peter Dimov	26ce33597d	Regenerate CMakeLists.txt	2021-09-21 14:45:20 +03:00
Peter Dimov	c89713b978	Add CMake tests to ci.yml	2021-09-21 14:31:47 +03:00
Peter Dimov	10c441c8d7	Update appveyor.yml	2021-09-15 15:11:54 +03:00
Peter Dimov	09ec260780	Document operator<<	2021-09-15 03:53:13 +03:00
Peter Dimov	2da13befd7	Work around mysterious errors with gcc, msvc-14.1, and clang-cl	2021-09-15 03:28:29 +03:00
Peter Dimov	e668c099ce	Add operator<< for variant	2021-09-15 02:51:11 +03:00
Peter Dimov	aebcb9792d	Update documentation of visit_by_index	2021-09-15 02:00:33 +03:00
Peter Dimov	8fd9f830a9	Add proper type deduction to visit_by_index	2021-09-15 01:30:09 +03:00
Peter Dimov	ed4bebff3d	Document visit_by_index	2021-09-14 21:32:57 +03:00
Peter Dimov	ad06c9b923	Add visit_by_index	2021-09-14 21:06:01 +03:00
Peter Dimov	de4eb8b6d2	Update README.md	2021-09-11 19:47:34 +03:00
Peter Dimov	4d69db1441	Extend g++-10 workarounds to 11	2021-09-11 19:23:39 +03:00
Peter Dimov	095d9770c4	Update ci.yml	2021-09-11 18:36:43 +03:00
Peter Dimov	cca476fbbc	Update documentation	2021-09-11 18:29:17 +03:00
Peter Dimov	c76af4d3cf	Update README.md	2021-09-11 18:26:28 +03:00
Peter Dimov	1af7b165cf	BOOST_VARIANT2_CX14_ASSERT must be empty under C++11	2021-09-11 18:22:46 +03:00
Peter Dimov	49bff72be0	Define and use a helper macro BOOST_VARIANT2_CX14_ASSERT in constexpr functions	2021-09-11 18:11:17 +03:00
Peter Dimov	59780ba08e	Only assert when C++14	2021-09-11 18:00:29 +03:00
Peter Dimov	edd70cfd66	Update ci.yml	2021-09-11 17:43:05 +03:00
Peter Dimov	86c2782dff	Update documentation	2021-09-11 17:39:55 +03:00
Peter Dimov	dce8174550	Make unsafe_get public	2021-09-11 17:29:21 +03:00
Peter Dimov	9d40bc80f1	Use BOOST_ASSERT instead of assert	2021-09-11 17:23:29 +03:00
Peter Dimov	be6ddf9fdc	Add boost/variant2.hpp	2021-09-11 17:19:09 +03:00
Peter Dimov	4153a535a0	Update .github/workflows	2021-04-19 20:37:12 +03:00
Peter Dimov	f374ad68a3	Add -DBUILD_TESTING=ON to .yml files; it's not default anymore	2021-03-19 04:18:08 +02:00
Peter Dimov	3bc9a57c9b	Merge branch 'feature/issue-26' into develop	2021-03-13 18:23:39 +02:00
Peter Dimov	3ca95a65df	Use boost::hash in hash_value, not std::hash (closes #27 )	2021-03-13 05:08:03 +02:00
Peter Dimov	ae1f72671e	Add test for types supported by boost::hash, but not by std::hash	2021-03-13 04:50:01 +02:00
Peter Dimov	a2dab8c7d3	Refactor detail::hash_value_L	2021-03-13 04:10:41 +02:00
Peter Dimov	f39a71ed2f	Merge branch 'feature/issue-26-nofix' into feature/issue-26	2021-03-13 01:09:46 +02:00
Peter Dimov	06dde96400	Merge branch 'develop' into feature/issue-26-nofix	2021-03-13 01:09:17 +02:00
Peter Dimov	8be0a4a5fe	Update copyright	2021-03-12 23:42:32 +02:00
Peter Dimov	90cda5339f	Disable U&& constructor for derived types	2021-03-12 23:40:14 +02:00
Peter Dimov	afb0aafd64	Change clangs to bionic	2021-03-12 20:18:24 +02:00
Peter Dimov	f586dc8848	Add test for inherited constructors (refs #26 )	2021-03-12 20:15:09 +02:00
Peter Dimov	20b9175932	Add cxxstd=latest to Appveyor	2021-03-08 04:04:35 +02:00
Peter Dimov	fb3ce863ff	Add MSVC workaround for monospace constexpr (refs #25 )	2021-03-08 03:26:40 +02:00
Peter Dimov	8ec0bf448a	Add monospace relational tests (refs #25 )	2021-03-08 03:01:21 +02:00
Peter Dimov	6d19e6be68	Update revision history	2021-03-07 00:51:28 +02:00
Peter Dimov	d8552b23ae	UBSan on clang 7 is broken on Ubuntu	2021-03-01 06:35:38 +02:00
Peter Dimov	f44aba09a2	Update .travis.yml	2021-03-01 00:26:43 +02:00
Peter Dimov	99cc1db385	Fix documentation for emplace effects	2021-01-25 03:49:42 +02:00
Peter Dimov	6d848c5af6	Update GCC workarounds in constexpr in-place construct tests	2021-01-25 03:44:24 +02:00
Peter Dimov	3c9f4e56bf	Fix visit codegen regression when NDEBUG is not defined	2021-01-24 17:27:24 +02:00
Peter Dimov	3015e56bcb	GCC bug 63707 has been fixed for GCC 11	2021-01-23 20:36:12 +02:00
Peter Dimov	7c37053950	Merge branch 'develop' into feature/double-opt	2021-01-13 05:06:00 +02:00
Peter Dimov	60995edb41	Remove g++ 4.7 from GHA	2021-01-13 05:01:44 +02:00
Peter Dimov	84a2c175d0	Use variant=release for variant_visit_r under g++/windows	2021-01-13 04:44:56 +02:00
Peter Dimov	ea3268feb4	Add .github/workflows	2021-01-13 04:19:15 +02:00
Peter Dimov	6de876954a	Merge branch 'develop' into feature/double-opt	2021-01-13 02:32:32 +02:00
Peter Dimov	efc1d5acca	Add more tests to variant_emplace_index.cpp	2021-01-13 02:32:05 +02:00
Peter Dimov	453b00dec8	Use (i+1)*2+j for the internal index in the double-buffered case, to avoid branches	2021-01-13 02:10:12 +02:00
Peter Dimov	c6186e0a95	Merge pull request #22 from eldiener/develop Add "cxxstd" json field. The "cxxstd" json field is being added to ea…	2020-12-16 18:45:01 +02:00
Edward Diener	24ccee2104	Add "cxxstd" json field. The "cxxstd" json field is being added to each Boost library's meta json information for libraries whose minumum C++ standard compilation level is C++11 on up. The value of this field matches one of the values for 'cxxstd' in Boost.Build. The purpose of doing this is to provide information for the Boost website documentation for each library which will specify the minimum C++ standard compilation that an end-user must employ in order to use the particular library. This will aid end-users who want to know if they can successfully use a Boost library based on their C++ compiler's compilation level, without having to search the library's documentation to find this out.	2020-12-16 01:45:24 -05:00
Peter Dimov	93b8618e94	Update maintainer e-mail	2020-12-12 01:08:09 +02:00