Update revision history

Correct CMake version check; VERSION_GREATER 3.18 is true for 3.18.1
BOOST_TEST_THROWS requires a semicolon after https://github.com/boostorg/core/pull/205
2025-12-23 15:18:10 +01:00 · 2025-10-22 21:03:21 +03:00 · 2025-10-19 21:07:20 +03:00 · 2025-10-18 20:23:49 +03:00 · 2025-10-18 08:24:39 +03:00 · 2025-10-18 03:12:52 +03:00
28 changed files with 1468 additions and 263 deletions
--- a/.drone.jsonnet
+++ b/.drone.jsonnet
@@ -32,6 +32,8 @@ local linux_pipeline(name, image, environment, packages = "", sources = [], arch
            commands:
            [
                'set -e',
+                'uname -a',
+                'echo $DRONE_STAGE_MACHINE',
                '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 []) +
@@ -97,258 +99,307 @@ local windows_pipeline(name, image, environment, arch = "amd64") =

 [
    linux_pipeline(
-        "Linux 14.04 GCC 4.8* 32/64",
-        "cppalliance/droneubuntu1404:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11', ADDRMD: '32,64' },
+        "Linux 16.04 GCC 4.8 32/64",
+        "cppalliance/droneubuntu1604:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-4.8', CXXSTD: '11', ADDRMD: '32,64' },
+        "g++-4.8-multilib",
    ),

    linux_pipeline(
-        "Linux 14.04 GCC 4.9 32/64",
-        "cppalliance/droneubuntu1404:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++-4.9', CXXSTD: '03,11', ADDRMD: '32,64' },
+        "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",
-        [ "ppa:ubuntu-toolchain-r/test" ],
    ),

    linux_pipeline(
        "Linux 16.04 GCC 5* 32/64",
        "cppalliance/droneubuntu1604:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11,14', ADDRMD: '32,64' },
+        { 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: '03,11,14', ADDRMD: '32,64' },
+        { 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: '03,11,14,17', ADDRMD: '32,64' },
+        { 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: '03,11,14,17', ADDRMD: '32,64' },
+        { 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: '03,11,14,17,2a', ADDRMD: '32,64' },
+        { 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: '03,11,14,17,2a' },
+        { 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: '03,11,14,17,2a' },
+        { 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: '03,11,14,17,20', ADDRMD: '32,64' },
+        { 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: '03,11,14,17,2a', ADDRMD: '32,64' },
+        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '11,14,17,2a', ADDRMD: '32,64' },
    ),

    linux_pipeline(
-        "Linux 22.04 GCC 12 32 ASAN",
+        "Linux 22.04 GCC 12 32/64",
        "cppalliance/droneubuntu2204:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '03,11,14,17,20,2b', ADDRMD: '32' } + asan,
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '11,14,17,20,2b', ADDRMD: '32,64' },
        "g++-12-multilib",
    ),

    linux_pipeline(
-        "Linux 22.04 GCC 12 64 ASAN",
-        "cppalliance/droneubuntu2204:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '03,11,14,17,20,2b', ADDRMD: '64' } + asan,
-        "g++-12-multilib",
-    ),
-
-    linux_pipeline(
-        "Linux 23.04 GCC 13 32/64",
-        "cppalliance/droneubuntu2304:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++-13', CXXSTD: '03,11,14,17,20,2b', ADDRMD: '32,64' },
+        "Linux 24.04 GCC 13 32/64",
+        "cppalliance/droneubuntu2404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-13', CXXSTD: '11,14,17,20,2b', ADDRMD: '32,64' },
        "g++-13-multilib",
    ),

+    linux_pipeline(
+        "Linux 24.04 GCC 14 32 ASAN",
+        "cppalliance/droneubuntu2404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-14', CXXSTD: '11,14,17,20,2b', ADDRMD: '32' } + asan,
+        "g++-14-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 24.04 GCC 14 64 ASAN",
+        "cppalliance/droneubuntu2404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-14', CXXSTD: '11,14,17,20,2b', ADDRMD: '64' } + asan,
+        "g++-14-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 24.04 GCC 14 32 UBSAN",
+        "cppalliance/droneubuntu2404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-14', CXXSTD: '11,14,17,20,2b', ADDRMD: '32' } + ubsan,
+        "g++-14-multilib",
+    ),
+
+    linux_pipeline(
+        "Linux 24.04 GCC 14 64 UBSAN",
+        "cppalliance/droneubuntu2404:1",
+        { TOOLSET: 'gcc', COMPILER: 'g++-14', CXXSTD: '11,14,17,20,2b', ADDRMD: '64' } + ubsan,
+        "g++-14-multilib",
+    ),
+
    linux_pipeline(
        "Linux 16.04 Clang 3.5",
        "cppalliance/droneubuntu1604:1",
-        { TOOLSET: 'clang', COMPILER: 'clang++-3.5', CXXSTD: '03,11' },
+        { 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: '03,11,14' },
+        { 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: '03,11,14' },
+        { 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: '03,11,14' },
+        { 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: '03,11,14' },
+        { 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: '03,11,14' },
+        { 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: '03,11,14,1z' },
+        { TOOLSET: 'clang', COMPILER: 'clang++-5.0', CXXSTD: '11,14' },
        "clang-5.0",
    ),

    linux_pipeline(
        "Linux 18.04 Clang 6.0",
        "cppalliance/droneubuntu1804:1",
-        { TOOLSET: 'clang', COMPILER: 'clang++-6.0', CXXSTD: '03,11,14,17' },
+        { 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: '03,11,14,17' },
+        { 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: '03,11,14,17' },
+        { 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: '03,11,14,17,2a' },
+        { 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: '03,11,14,17,2a' },
+        { 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: '03,11,14,17,2a' },
+        { 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: '03,11,14,17,2a' },
+        { 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: '03,11,14,17,20,2b' },
+        { 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: '03,11,14,17,20,2b' },
+        { TOOLSET: 'clang', COMPILER: 'clang++-14', CXXSTD: '11,14,17,20,2b' },
        "clang-14",
    ),

    linux_pipeline(
-        "Linux 22.04 Clang 15 UBSAN",
+        "Linux 22.04 Clang 15",
        "cppalliance/droneubuntu2204:1",
-        { TOOLSET: 'clang', COMPILER: 'clang++-15', CXXSTD: '03,11,14,17,20,2b' } + ubsan,
+        { TOOLSET: 'clang', COMPILER: 'clang++-15', CXXSTD: '11,14,17,20,2b' },
        "clang-15",
    ),

    linux_pipeline(
-        "Linux 22.04 Clang 15 ASAN",
-        "cppalliance/droneubuntu2204:1",
-        { TOOLSET: 'clang', COMPILER: 'clang++-15', CXXSTD: '03,11,14,17,20,2b' } + asan,
-        "clang-15",
-    ),
-
-    linux_pipeline(
-        "Linux 23.04 Clang 16",
-        "cppalliance/droneubuntu2304:1",
-        { TOOLSET: 'clang', COMPILER: 'clang++-16', CXXSTD: '03,11,14,17,20,2b' },
+        "Linux 24.04 Clang 16",
+        "cppalliance/droneubuntu2404:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-16', CXXSTD: '11,14,17,20,2b' },
        "clang-16",
    ),

+    linux_pipeline(
+        "Linux 24.04 Clang 17 UBSAN",
+        "cppalliance/droneubuntu2404:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-17', CXXSTD: '11,14,17,20,2b' } + ubsan,
+        "clang-17",
+    ),
+
+    linux_pipeline(
+        "Linux 24.04 Clang 17 ASAN",
+        "cppalliance/droneubuntu2404:1",
+        { 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",
+    ),
+
+    linux_pipeline(
+        "Linux 24.10 Clang 19",
+        "cppalliance/droneubuntu2410:1",
+        { TOOLSET: 'clang', COMPILER: 'clang++-19', CXXSTD: '11,14,17,20,2b' } + asan,
+        "clang-19",
+    ),
+
    macos_pipeline(
        "MacOS 10.15 Xcode 12.2 UBSAN",
-        { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '03,11,14,1z' } + ubsan,
+        { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '11,14,1z' } + ubsan,
    ),

    macos_pipeline(
        "MacOS 10.15 Xcode 12.2 ASAN",
-        { TOOLSET: 'clang', COMPILER: 'clang++', CXXSTD: '03,11,14,1z' } + 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: '03,11,14,17,20,2b' } + 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: '03,11,14,17,20,2b' } + 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' },
+        { TOOLSET: 'msvc-14.0', CXXSTD: '14,latest', B2_DONT_EMBED_MANIFEST: '1' },
    ),

    windows_pipeline(
@@ -358,9 +409,9 @@ local windows_pipeline(name, image, environment, arch = "amd64") =
    ),

    windows_pipeline(
-        "Windows VS2017 msvc-14.1 Strict",
+        "Windows VS2017 msvc-14.1 permissive-",
        "cppalliance/dronevs2017",
-        { TOOLSET: 'msvc-14.1', CXXSTD: '14,17,latest', CXXFLAGS: '/permissive-' },
+        { TOOLSET: 'msvc-14.1', CXXSTD: '14,17', CXXFLAGS: '/permissive-' },
    ),

    windows_pipeline(
@@ -370,9 +421,9 @@ local windows_pipeline(name, image, environment, arch = "amd64") =
    ),

    windows_pipeline(
-        "Windows VS2019 msvc-14.2 Strict",
+        "Windows VS2019 msvc-14.2 permissive-",
        "cppalliance/dronevs2019",
-        { TOOLSET: 'msvc-14.2', CXXSTD: '14,17,20,latest', CXXFLAGS: '/permissive-' },
+        { TOOLSET: 'msvc-14.2', CXXSTD: '14,17', CXXFLAGS: '/permissive-' },
    ),

    windows_pipeline(
@@ -380,4 +431,10 @@ local windows_pipeline(name, image, environment, arch = "amd64") =
        "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/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -18,129 +18,219 @@ jobs:
      matrix:
        include:
          - toolset: gcc-4.8
-            cxxstd: "03,11"
+            cxxstd: "11"
+            container: ubuntu:16.04
            os: ubuntu-latest
-            container: ubuntu:18.04
            install: g++-4.8
-          - toolset: gcc-5
-            cxxstd: "03,11,14,1z"
+          - 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: "03,11,14,1z"
-            os: ubuntu-latest
+            cxxstd: "11,14,1z"
            container: ubuntu:18.04
+            os: ubuntu-latest
            install: g++-6
          - toolset: gcc-7
-            cxxstd: "03,11,14,17"
-            os: ubuntu-latest
+            cxxstd: "11,14,17"
            container: ubuntu:18.04
+            os: ubuntu-latest
          - toolset: gcc-8
-            cxxstd: "03,11,14,17,2a"
-            os: ubuntu-20.04
+            cxxstd: "11,14,17,2a"
+            container: ubuntu:20.04
+            os: ubuntu-latest
            install: g++-8
          - toolset: gcc-9
-            cxxstd: "03,11,14,17,2a"
-            os: ubuntu-20.04
+            cxxstd: "11,14,17,2a"
+            container: ubuntu:20.04
+            os: ubuntu-latest
          - toolset: gcc-10
-            cxxstd: "03,11,14,17,2a"
-            os: ubuntu-20.04
+            cxxstd: "11,14,17,2a"
+            container: ubuntu:22.04
+            os: ubuntu-latest
            install: g++-10
          - toolset: gcc-11
-            cxxstd: "03,11,14,17,2a"
-            os: ubuntu-20.04
+            cxxstd: "11,14,17,2a"
+            container: ubuntu:22.04
+            os: ubuntu-latest
            install: g++-11
          - toolset: gcc-12
-            cxxstd: "03,11,14,17,20,2b"
-            os: ubuntu-22.04
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:22.04
+            os: ubuntu-latest
            install: g++-12
+          - toolset: gcc-13
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:24.04
+            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: gcc-15
+            cxxstd: "11,14,17,20,23,2c"
+            container: ubuntu:25.04
+            os: ubuntu-latest
+            install: g++-15
          - toolset: clang
            compiler: clang++-3.9
-            cxxstd: "03,11,14"
-            os: ubuntu-latest
+            cxxstd: "11,14"
            container: ubuntu:18.04
+            os: ubuntu-latest
            install: clang-3.9
          - toolset: clang
            compiler: clang++-4.0
-            cxxstd: "03,11,14"
-            os: ubuntu-latest
+            cxxstd: "11,14"
            container: ubuntu:18.04
+            os: ubuntu-latest
            install: clang-4.0
          - toolset: clang
            compiler: clang++-5.0
-            cxxstd: "03,11,14,1z"
-            os: ubuntu-latest
+            cxxstd: "11,14"
            container: ubuntu:18.04
+            os: ubuntu-latest
            install: clang-5.0
          - toolset: clang
            compiler: clang++-6.0
-            cxxstd: "03,11,14,17"
-            os: ubuntu-20.04
+            cxxstd: "11,14,17"
+            container: ubuntu:20.04
+            os: ubuntu-latest
            install: clang-6.0
          - toolset: clang
            compiler: clang++-7
-            cxxstd: "03,11,14,17"
-            os: ubuntu-20.04
+            cxxstd: "11,14,17"
+            container: ubuntu:20.04
+            os: ubuntu-latest
            install: clang-7
          - toolset: clang
            compiler: clang++-8
-            cxxstd: "03,11,14,17"
-            os: ubuntu-20.04
+            cxxstd: "11,14,17"
+            container: ubuntu:20.04
+            os: ubuntu-latest
            install: clang-8
          - toolset: clang
            compiler: clang++-9
-            cxxstd: "03,11,14,17,2a"
-            os: ubuntu-20.04
+            cxxstd: "11,14,17,2a"
+            container: ubuntu:20.04
+            os: ubuntu-latest
            install: clang-9
          - toolset: clang
            compiler: clang++-10
-            cxxstd: "03,11,14,17,2a"
-            os: ubuntu-20.04
+            cxxstd: "11,14,17,2a"
+            container: ubuntu:20.04
+            os: ubuntu-latest
            install: clang-10
          - toolset: clang
            compiler: clang++-11
-            cxxstd: "03,11,14,17,2a"
-            os: ubuntu-20.04
+            cxxstd: "11,14,17,2a"
+            container: ubuntu:20.04
+            os: ubuntu-latest
            install: clang-11
          - toolset: clang
            compiler: clang++-12
-            cxxstd: "03,11,14,17,2a"
-            os: ubuntu-20.04
+            cxxstd: "11,14,17,2a"
+            container: ubuntu:20.04
+            os: ubuntu-latest
            install: clang-12
          - toolset: clang
            compiler: clang++-13
-            cxxstd: "03,11,14,17,20,2b"
-            os: ubuntu-22.04
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:22.04
+            os: ubuntu-latest
            install: clang-13
          - toolset: clang
            compiler: clang++-14
-            cxxstd: "03,11,14,17,20,2b"
-            os: ubuntu-22.04
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:22.04
+            os: ubuntu-latest
            install: clang-14
          - toolset: clang
-            cxxstd: "03,11,14,17,2a"
-            os: macos-11
+            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:24.04
+            os: ubuntu-latest
+            install: clang-16
+          - toolset: clang
+            compiler: clang++-17
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:24.04
+            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
+            compiler: clang++-19
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:24.04
+            os: ubuntu-latest
+            install: clang-19
+          - toolset: clang
+            compiler: clang++-20
+            cxxstd: "11,14,17,20,23,2c"
+            container: ubuntu:25.04
+            os: ubuntu-latest
+            install: clang-20
+          - toolset: clang
+            cxxstd: "11,14,17,20,2b"
+            os: macos-13
+          - toolset: clang
+            cxxstd: "11,14,17,20,2b"
+            os: macos-14
+          - toolset: clang
+            cxxstd: "11,14,17,20,2b"
+            os: macos-15

    runs-on: ${{matrix.os}}
-    container: ${{matrix.container}}
+
+    container:
+      image: ${{matrix.container}}
+      volumes:
+        - /node20217:/node20217:rw,rshared
+        - ${{ startsWith(matrix.container, 'ubuntu:1') && '/node20217:/__e/node20:ro,rshared' || ' ' }}

    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 python git g++
+          apt-get -y install sudo python3 git g++ curl xz-utils
+
+      - name: Install nodejs20glibc2.17
+        if: ${{ startsWith( matrix.container, 'ubuntu:1' ) }}
+        run: |
+          curl -LO https://archives.boost.io/misc/node/node-v20.9.0-linux-x64-glibc-217.tar.xz
+          tar -xf node-v20.9.0-linux-x64-glibc-217.tar.xz --strip-components 1 -C /node20217
+          ldd /__e/node20/bin/node
+
+      - uses: actions/checkout@v4

      - name: Install packages
        if: matrix.install
-        run: sudo apt-get -y install ${{matrix.install}}
+        run: |
+          sudo apt-get update
+          sudo apt-get -y install ${{matrix.install}}

      - name: Setup Boost
        run: |
@@ -160,7 +250,7 @@ jobs:
          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
+          python3 tools/boostdep/depinst/depinst.py $LIBRARY
          ./bootstrap.sh
          ./b2 -d0 headers

@@ -179,14 +269,6 @@ jobs:
      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
@@ -196,14 +278,14 @@ jobs:
            addrmd: 32,64
            os: windows-2022
          - toolset: gcc
-            cxxstd: "03,11,14,17,2a"
+            cxxstd: "11,14,17,2a"
            addrmd: 64
-            os: windows-2019
+            os: windows-2022

    runs-on: ${{matrix.os}}

    steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4

      - name: Setup Boost
        shell: cmd
@@ -231,21 +313,23 @@ jobs:
        shell: cmd
        run: |
          cd ../boost-root
-          b2 -j3 libs/%LIBRARY%/test toolset=${{matrix.toolset}} cxxstd=${{matrix.cxxstd}} address-model=${{matrix.addrmd}} variant=debug,release embed-manifest-via=linker
+          b2 -j2 libs/%LIBRARY%/test toolset=${{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: ubuntu-24.04
+          - os: macos-13
+          - os: macos-14
+          - os: macos-15

    runs-on: ${{matrix.os}}

    steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4

      - name: Install packages
        if: matrix.install
@@ -284,14 +368,16 @@ jobs:
      fail-fast: false
      matrix:
        include:
-          - os: ubuntu-20.04
          - os: ubuntu-22.04
-          - os: macos-11
+          - os: ubuntu-24.04
+          - os: macos-13
+          - os: macos-14
+          - os: macos-15

    runs-on: ${{matrix.os}}

    steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4

      - name: Install packages
        if: matrix.install
@@ -340,14 +426,16 @@ jobs:
      fail-fast: false
      matrix:
        include:
-          - os: ubuntu-20.04
          - os: ubuntu-22.04
-          - os: macos-11
+          - os: ubuntu-24.04
+          - os: macos-13
+          - os: macos-14
+          - os: macos-15

    runs-on: ${{matrix.os}}

    steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4

      - name: Install packages
        if: matrix.install
@@ -388,3 +476,180 @@ jobs:
        run: |
          cd ../boost-root/__build__
          ctest --output-on-failure --no-tests=error
+
+  windows-cmake-subdir:
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: windows-latest
+
+    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-latest
+
+    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-latest
+
+    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/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -19,7 +19,7 @@ target_link_libraries(boost_variant2
    Boost::mp11
 )

-if(CMAKE_VERSION VERSION_GREATER 3.18 AND CMAKE_GENERATOR MATCHES "Visual Studio")
+if(NOT CMAKE_VERSION VERSION_LESS 3.19 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")
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -59,7 +59,7 @@ test_script:
  - if not "%CXXSTD%" == "" set CXXSTD=cxxstd=%CXXSTD%
  - if not "%ADDRMD%" == "" set ADDRMD=address-model=%ADDRMD%
  - 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 "%CMAKE%%CMAKE_SUBDIR%%CMAKE_INSTALL%" == ""  b2 -j2 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 ..
--- a/build.jam
+++ b/build.jam
@@ -0,0 +1,22 @@
+# Copyright 2023-2024 René Ferdinand Rivera Morell
+# Copyright 2024 Peter Dimov
+# Distributed under the Boost Software License, Version 1.0.
+# https://www.boost.org/LICENSE_1_0.txt
+
+require-b2 5.2 ;
+
+constant boost_dependencies :
+    /boost/assert//boost_assert
+    /boost/config//boost_config
+    /boost/mp11//boost_mp11
+    ;
+
+project /boost/variant2 ;
+
+explicit
+    [ alias boost_variant2 : : : : <include>include <library>$(boost_dependencies) ]
+    [ alias all : boost_variant2 test ]
+    ;
+
+call-if : boost-library variant2
+    ;
--- a/doc/variant2/changelog.adoc
+++ b/doc/variant2/changelog.adoc
@@ -1,5 +1,5 @@
 ////
-Copyright 2019-2022 Peter Dimov
+Copyright 2019-2025 Peter Dimov
 Distributed under the Boost Software License, Version 1.0.
 https://www.boost.org/LICENSE_1_0.txt
 ////
@@ -8,6 +8,19 @@ https://www.boost.org/LICENSE_1_0.txt
 # Revision History
 :idprefix: changelog_

+## Changes in 1.90.0
+
+* More functions have been marked as `constexpr`, including `~variant`.
+  This didn't matter before {cpp}20, but does now.
+
+## Changes in 1.88.0
+
+* Use the smallest appropriate unsigned type for the index.
+
+## 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`.
--- a/doc/variant2/reference.adoc
+++ b/doc/variant2/reference.adoc
@@ -157,7 +157,7 @@ template<class R = /*unspecified*/, class F, class... V>
 // visit_by_index (extension)

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

 // monostate

@@ -250,6 +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*/ );
@@ -570,6 +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

 ```
@@ -922,7 +936,7 @@ Remarks: :: If `R` is given explicitly, as in `visit<int>`, the return

 ```
 template<class R = /*unspecified*/, class V, class... F>
-  constexpr /*see below*/ visit_by_index(V&& v, F&&.. f);
+  constexpr /*see below*/ visit_by_index(V&& v, F&&... f);
 ```
 [none]
 * {blank}
--- a/extra/boost_variant2.natvis
+++ b/extra/boost_variant2.natvis
@@ -1,32 +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_ma_base_impl&lt;*&gt;" Inheritable="true">
-        <Intrinsic Name="index" Expression="$T2==1?((int)ix_-1):((int)((ix_-2)/2))"/>
-        <DisplayString Condition="index()==0&amp;&amp;$T2==1" Optional="true">{st_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==1&amp;&amp;$T2==1" Optional="true">{st_.rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==2&amp;&amp;$T2==1" Optional="true">{st_.rest_.rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==3&amp;&amp;$T2==1" Optional="true">{st_.rest_.rest_.rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==4&amp;&amp;$T2==1" Optional="true">{st_.rest_.rest_.rest_.rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==5&amp;&amp;$T2==1" Optional="true">{st_.rest_.rest_.rest_.rest_.rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==6&amp;&amp;$T2==1" Optional="true">{st_.rest_.rest_.rest_.rest_.rest_.rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==7&amp;&amp;$T2==1" Optional="true">{st_.rest_.rest_.rest_.rest_.rest_.rest_.rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==8&amp;&amp;$T2==1" Optional="true">{st_.rest_.rest_.rest_.rest_.rest_.rest_.rest_.rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==9&amp;&amp;$T2==1" Optional="true">{st_.rest_.rest_.rest_.rest_.rest_.rest_.rest_.rest_.rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==0&amp;&amp;$T2==0" Optional="true">{st_[ix_%2].rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==1&amp;&amp;$T2==0" Optional="true">{st_[ix_%2].rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==2&amp;&amp;$T2==0" Optional="true">{st_[ix_%2].rest_.rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==3&amp;&amp;$T2==0" Optional="true">{st_[ix_%2].rest_.rest_.rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==4&amp;&amp;$T2==0" Optional="true">{st_[ix_%2].rest_.rest_.rest_.rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==5&amp;&amp;$T2==0" Optional="true">{st_[ix_%2].rest_.rest_.rest_.rest_.rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==6&amp;&amp;$T2==0" Optional="true">{st_[ix_%2].rest_.rest_.rest_.rest_.rest_.rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==7&amp;&amp;$T2==0" Optional="true">{st_[ix_%2].rest_.rest_.rest_.rest_.rest_.rest_.rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==8&amp;&amp;$T2==0" Optional="true">{st_[ix_%2].rest_.rest_.rest_.rest_.rest_.rest_.rest_.rest_.rest_.first_} ({index()})</DisplayString>
-        <DisplayString Condition="index()==9&amp;&amp;$T2==0" Optional="true">{st_[ix_%2].rest_.rest_.rest_.rest_.rest_.rest_.rest_.rest_.rest_.rest_.first_} ({index()})</DisplayString>
-        <Expand>
-            <Item Name="[index]">index()</Item>
-            <Item Name="ix_">ix_</Item>
-        </Expand>
-    </Type>
+  <Type Name="boost::variant2::detail::variant_base_impl&lt;*,1,*&gt;">
+    <Intrinsic Name="index" Expression="(int)ix_ - 1"/>
+    <DisplayString Condition="index() ==  0" Optional="true">{{ index=0, value={*($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/variant.hpp
+++ b/include/boost/variant2/variant.hpp
@@ -18,16 +18,24 @@
 #include <boost/assert/source_location.hpp>
 #include <boost/config.hpp>
 #include <boost/config/workaround.hpp>
-#include <boost/cstdint.hpp>
 #include <cstddef>
 #include <type_traits>
 #include <exception>
-#include <initializer_list>
 #include <utility>
-#include <functional> // std::hash
+#include <typeindex> // std::hash
 #include <iosfwd>
 #include <cstdint>
 #include <cerrno>
+#include <limits>
+
+//
+
+// constexpr destructors
+#if defined(__cpp_constexpr_dynamic_alloc) && __cpp_constexpr_dynamic_alloc >= 201907L
+# define BOOST_VARIANT2_CXX20_CONSTEXPR constexpr
+#else
+# define BOOST_VARIANT2_CXX20_CONSTEXPR
+#endif

 //

@@ -85,7 +93,7 @@ struct monostate
 {
 };

-#if !BOOST_WORKAROUND(BOOST_MSVC, < 1940)
+#if !BOOST_WORKAROUND(BOOST_MSVC, < 1950)

 constexpr bool operator<(monostate, monostate) noexcept { return false; }
 constexpr bool operator>(monostate, monostate) noexcept { return false; }
@@ -558,16 +566,16 @@ template<class T1, class... T> union variant_storage_impl<mp11::mp_false, T1, T.
    {
    }

-    ~variant_storage_impl()
+    BOOST_VARIANT2_CXX20_CONSTEXPR ~variant_storage_impl()
    {
    }

-    template<class... A> void emplace( mp11::mp_size_t<0>, A&&... a )
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace( mp11::mp_size_t<0>, A&&... a )
    {
        ::new( &first_ ) T1( std::forward<A>(a)... );
    }

-    template<std::size_t I, class... A> void emplace( mp11::mp_size_t<I>, A&&... a )
+    template<std::size_t I, class... A> BOOST_CXX14_CONSTEXPR void emplace( mp11::mp_size_t<I>, A&&... a )
    {
        rest_.emplace( mp11::mp_size_t<I-1>(), std::forward<A>(a)... );
    }
@@ -607,22 +615,22 @@ template<class T0, class T1, class T2, class T3, class T4, class T5, class T6, c

    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()
+    BOOST_VARIANT2_CXX20_CONSTEXPR ~variant_storage_impl()
    {
    }

-    template<class... A> void emplace( mp11::mp_size_t<0>, A&&... a ) { ::new( &t0_ ) T0( std::forward<A>(a)... ); }
-    template<class... A> void emplace( mp11::mp_size_t<1>, A&&... a ) { ::new( &t1_ ) T1( std::forward<A>(a)... ); }
-    template<class... A> void emplace( mp11::mp_size_t<2>, A&&... a ) { ::new( &t2_ ) T2( std::forward<A>(a)... ); }
-    template<class... A> void emplace( mp11::mp_size_t<3>, A&&... a ) { ::new( &t3_ ) T3( std::forward<A>(a)... ); }
-    template<class... A> void emplace( mp11::mp_size_t<4>, A&&... a ) { ::new( &t4_ ) T4( std::forward<A>(a)... ); }
-    template<class... A> void emplace( mp11::mp_size_t<5>, A&&... a ) { ::new( &t5_ ) T5( std::forward<A>(a)... ); }
-    template<class... A> void emplace( mp11::mp_size_t<6>, A&&... a ) { ::new( &t6_ ) T6( std::forward<A>(a)... ); }
-    template<class... A> void emplace( mp11::mp_size_t<7>, A&&... a ) { ::new( &t7_ ) T7( std::forward<A>(a)... ); }
-    template<class... A> void emplace( mp11::mp_size_t<8>, A&&... a ) { ::new( &t8_ ) T8( std::forward<A>(a)... ); }
-    template<class... A> void emplace( mp11::mp_size_t<9>, A&&... a ) { ::new( &t9_ ) T9( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace( mp11::mp_size_t<0>, A&&... a ) { ::new( &t0_ ) T0( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace( mp11::mp_size_t<1>, A&&... a ) { ::new( &t1_ ) T1( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace( mp11::mp_size_t<2>, A&&... a ) { ::new( &t2_ ) T2( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace( mp11::mp_size_t<3>, A&&... a ) { ::new( &t3_ ) T3( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace( mp11::mp_size_t<4>, A&&... a ) { ::new( &t4_ ) T4( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace( mp11::mp_size_t<5>, A&&... a ) { ::new( &t5_ ) T5( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace( mp11::mp_size_t<6>, A&&... a ) { ::new( &t6_ ) T6( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace( mp11::mp_size_t<7>, A&&... a ) { ::new( &t7_ ) T7( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace( mp11::mp_size_t<8>, A&&... a ) { ::new( &t8_ ) T8( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace( mp11::mp_size_t<9>, A&&... a ) { ::new( &t9_ ) T9( std::forward<A>(a)... ); }

-    template<std::size_t I, class... A> void emplace( mp11::mp_size_t<I>, A&&... a )
+    template<std::size_t I, class... A> BOOST_CXX14_CONSTEXPR void emplace( mp11::mp_size_t<I>, A&&... a )
    {
        rest_.emplace( mp11::mp_size_t<I-10>(), std::forward<A>(a)... );
    }
@@ -675,7 +683,7 @@ template<class T1, class... T> union variant_storage_impl<mp11::mp_true, T1, T..
    {
    }

-    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<0>, A&&... a )
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_false, mp11::mp_size_t<0>, A&&... a )
    {
        ::new( &first_ ) T1( std::forward<A>(a)... );
    }
@@ -691,8 +699,11 @@ template<class T1, class... T> union variant_storage_impl<mp11::mp_true, T1, T..
 # 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)
@@ -740,16 +751,16 @@ template<class T0, class T1, class T2, class T3, class T4, class T5, class T6, c

    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)... ); }
-    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<2>, A&&... a ) { ::new( &t2_ ) T2( std::forward<A>(a)... ); }
-    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<3>, A&&... a ) { ::new( &t3_ ) T3( std::forward<A>(a)... ); }
-    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<4>, A&&... a ) { ::new( &t4_ ) T4( std::forward<A>(a)... ); }
-    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<5>, A&&... a ) { ::new( &t5_ ) T5( std::forward<A>(a)... ); }
-    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<6>, A&&... a ) { ::new( &t6_ ) T6( std::forward<A>(a)... ); }
-    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<7>, A&&... a ) { ::new( &t7_ ) T7( std::forward<A>(a)... ); }
-    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<8>, A&&... a ) { ::new( &t8_ ) T8( std::forward<A>(a)... ); }
-    template<class... A> void emplace_impl( mp11::mp_false, mp11::mp_size_t<9>, A&&... a ) { ::new( &t9_ ) T9( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_false, mp11::mp_size_t<0>, A&&... a ) { ::new( &t0_ ) T0( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_false, mp11::mp_size_t<1>, A&&... a ) { ::new( &t1_ ) T1( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_false, mp11::mp_size_t<2>, A&&... a ) { ::new( &t2_ ) T2( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_false, mp11::mp_size_t<3>, A&&... a ) { ::new( &t3_ ) T3( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_false, mp11::mp_size_t<4>, A&&... a ) { ::new( &t4_ ) T4( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_false, mp11::mp_size_t<5>, A&&... a ) { ::new( &t5_ ) T5( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_false, mp11::mp_size_t<6>, A&&... a ) { ::new( &t6_ ) T6( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_false, mp11::mp_size_t<7>, A&&... a ) { ::new( &t7_ ) T7( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_false, mp11::mp_size_t<8>, A&&... a ) { ::new( &t8_ ) T8( std::forward<A>(a)... ); }
+    template<class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_false, mp11::mp_size_t<9>, A&&... a ) { ::new( &t9_ ) T9( std::forward<A>(a)... ); }

    template<std::size_t I, class... A> BOOST_CXX14_CONSTEXPR void emplace_impl( mp11::mp_false, mp11::mp_size_t<I>, A&&... a )
    {
@@ -844,6 +855,26 @@ template<class U, class... T> using resolve_overload_type = typename decltype( o

 template<class U, class... T> using resolve_overload_index = mp11::mp_find<mp11::mp_list<T...>, resolve_overload_type<U, T...>>;

+// index_type
+
+template<std::size_t N> using get_smallest_unsigned_type = mp11::mp_cond<
+
+    mp11::mp_bool< N <= (std::numeric_limits<unsigned char>::max)() >, unsigned char,
+    mp11::mp_bool< N <= (std::numeric_limits<unsigned short>::max)() >, unsigned short,
+    mp11::mp_true, unsigned
+
+>;
+
+#if BOOST_WORKAROUND( BOOST_CLANG_VERSION, < 30800 )
+
+template<bool Double, class... T> using get_index_type = unsigned short;
+
+#else
+
+template<bool Double, class... T> using get_index_type = get_smallest_unsigned_type< (Double + 1) * sizeof...(T) >;
+
+#endif
+
 // variant_base

 template<bool is_trivially_destructible, bool is_single_buffered, class... T> struct variant_base_impl;
@@ -854,8 +885,10 @@ struct none {};
 // trivially destructible, single buffered
 template<class... T> struct variant_base_impl<true, true, T...>
 {
+    using index_type = get_index_type<false, T...>;
+
    variant_storage<none, T...> st_;
-    unsigned ix_;
+    index_type ix_;

    constexpr variant_base_impl(): st_( mp11::mp_size_t<0>() ), ix_( 0 )
    {
@@ -866,9 +899,11 @@ template<class... T> struct variant_base_impl<true, true, T...>
    }

    // requires: ix_ == 0
-    template<class I, class... A> void _replace( I, A&&... a )
+    template<class I, class... A> BOOST_CXX14_CONSTEXPR void _replace( I, A&&... a )
    {
        ::new( &st_ ) variant_storage<none, T...>( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... );
+
+        static_assert( I::value + 1 <= (std::numeric_limits<index_type>::max)(), "" );
        ix_ = I::value + 1;
    }

@@ -879,7 +914,7 @@ template<class... T> struct variant_base_impl<true, true, T...>

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

        BOOST_ASSERT( ix_ == J );

@@ -888,7 +923,7 @@ template<class... T> struct variant_base_impl<true, true, T...>

    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;
+        // std::size_t const J = I+1;

        BOOST_VARIANT2_CX14_ASSERT( ix_ == I+1 )

@@ -900,6 +935,8 @@ template<class... T> struct variant_base_impl<true, true, T...>
        static_assert( std::is_nothrow_constructible<U, A&&...>::value, "Logic error: U must be nothrow constructible from A&&..." );

        st_.emplace( mp11::mp_size_t<J>(), std::forward<A>(a)... );
+
+        static_assert( J <= (std::numeric_limits<index_type>::max)(), "" );
        ix_ = J;
    }

@@ -910,6 +947,8 @@ template<class... T> struct variant_base_impl<true, true, T...>
        U tmp( std::forward<A>(a)... );

        st_.emplace( mp11::mp_size_t<J>(), std::move(tmp) );
+
+        static_assert( J <= (std::numeric_limits<index_type>::max)(), "" );
        ix_ = J;
    }

@@ -930,8 +969,10 @@ template<class... T> struct variant_base_impl<true, true, T...>
 // trivially destructible, double buffered
 template<class... T> struct variant_base_impl<true, false, T...>
 {
+    using index_type = get_index_type<true, T...>;
+
    variant_storage<none, T...> st_[ 2 ];
-    unsigned ix_;
+    index_type ix_;

    constexpr variant_base_impl(): st_{ { mp11::mp_size_t<0>() }, { mp11::mp_size_t<0>() } }, ix_( 0 )
    {
@@ -942,9 +983,11 @@ template<class... T> struct variant_base_impl<true, false, T...>
    }

    // requires: ix_ == 0
-    template<class I, class... A> void _replace( I, A&&... a )
+    template<class I, class... A> BOOST_CXX14_CONSTEXPR void _replace( I, A&&... a )
    {
        ::new( &st_[ 0 ] ) variant_storage<none, T...>( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... );
+
+        static_assert( ( I::value + 1 ) * 2 <= (std::numeric_limits<index_type>::max)(), "" );
        ix_ = ( I::value + 1 ) * 2;
    }

@@ -957,7 +1000,7 @@ template<class... T> struct variant_base_impl<true, false, T...>
    {
        BOOST_ASSERT( index() == I );

-        size_t const J = I+1;
+        std::size_t const J = I+1;

        constexpr mp11::mp_size_t<J> j{};
        return st_[ ix_ & 1 ].get( j );
@@ -967,7 +1010,7 @@ template<class... T> struct variant_base_impl<true, false, T...>
    {
        BOOST_VARIANT2_CX14_ASSERT( index() == I )

-        // size_t const J = I+1;
+        // std::size_t const J = I+1;
        // constexpr mp_size_t<J> j{};

        return st_[ ix_ & 1 ].get( mp11::mp_size_t<I+1>() );
@@ -975,13 +1018,14 @@ template<class... T> struct variant_base_impl<true, false, T...>

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

        unsigned i2 = 1 - ( ix_ & 1 );

        st_[ i2 ].emplace( mp11::mp_size_t<J>(), std::forward<A>(a)... );

-        ix_ = J * 2 + i2;
+        static_assert( J * 2 + 1 <= (std::numeric_limits<index_type>::max)(), "" );
+        ix_ = static_cast<index_type>( J * 2 + i2 );
    }

    static constexpr bool uses_double_storage() noexcept
@@ -993,8 +1037,10 @@ template<class... T> struct variant_base_impl<true, false, T...>
 // not trivially destructible, single buffered
 template<class... T> struct variant_base_impl<false, true, T...>
 {
+    using index_type = get_index_type<false, T...>;
+
    variant_storage<none, T...> st_;
-    unsigned ix_;
+    index_type ix_;

    constexpr variant_base_impl(): st_( mp11::mp_size_t<0>() ), ix_( 0 )
    {
@@ -1005,9 +1051,11 @@ template<class... T> struct variant_base_impl<false, true, T...>
    }

    // requires: ix_ == 0
-    template<class I, class... A> void _replace( I, A&&... a )
+    template<class I, class... A> BOOST_CXX14_CONSTEXPR void _replace( I, A&&... a )
    {
        ::new( &st_ ) variant_storage<none, T...>( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... );
+
+        static_assert( I::value + 1 <= (std::numeric_limits<index_type>::max)(), "" );
        ix_ = I::value + 1;
    }

@@ -1020,14 +1068,14 @@ template<class... T> struct variant_base_impl<false, true, T...>
    {
        variant_base_impl * this_;

-        template<class I> void operator()( I ) const noexcept
+        template<class I> BOOST_CXX14_CONSTEXPR void operator()( I ) const noexcept
        {
            using U = mp11::mp_at<mp11::mp_list<none, T...>, I>;
            this_->st_.get( I() ).~U();
        }
    };

-    void _destroy() noexcept
+    BOOST_CXX14_CONSTEXPR void _destroy() noexcept
    {
        if( ix_ > 0 )
        {
@@ -1035,7 +1083,7 @@ template<class... T> struct variant_base_impl<false, true, T...>
        }
    }

-    ~variant_base_impl() noexcept
+    BOOST_VARIANT2_CXX20_CONSTEXPR ~variant_base_impl() noexcept
    {
        _destroy();
    }
@@ -1047,7 +1095,7 @@ template<class... T> struct variant_base_impl<false, true, T...>

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

        BOOST_ASSERT( ix_ == J );

@@ -1056,16 +1104,16 @@ template<class... T> struct variant_base_impl<false, true, T...>

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

        using U = mp11::mp_at_c<variant<T...>, I>;

@@ -1076,6 +1124,8 @@ template<class... T> struct variant_base_impl<false, true, T...>
        _destroy();

        st_.emplace( mp11::mp_size_t<J>(), std::move(tmp) );
+
+        static_assert( J <= (std::numeric_limits<index_type>::max)(), "" );
        ix_ = J;
    }

@@ -1088,12 +1138,14 @@ template<class... T> struct variant_base_impl<false, true, T...>
 // not trivially destructible, double buffered
 template<class... T> struct variant_base_impl<false, false, T...>
 {
+    using index_type = get_index_type<true, T...>;
+
 #if defined(__GNUC__) && __GNUC__ < 11 && !defined(__clang__) && !defined(__INTEL_COMPILER)

    // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63707 :-(

    variant_storage<none, T...> st1_, st2_;
-    unsigned ix_;
+    index_type ix_;

    constexpr variant_base_impl(): st1_( mp11::mp_size_t<0>() ), st2_( mp11::mp_size_t<0>() ), ix_( 0 )
    {
@@ -1116,7 +1168,7 @@ template<class... T> struct variant_base_impl<false, false, T...>
 #else

    variant_storage<none, T...> st_[ 2 ];
-    unsigned ix_;
+    index_type ix_;

    constexpr variant_base_impl(): st_{ { mp11::mp_size_t<0>() }, { mp11::mp_size_t<0>() } }, ix_( 0 )
    {
@@ -1139,9 +1191,11 @@ template<class... T> struct variant_base_impl<false, false, T...>
 #endif

    // requires: ix_ == 0
-    template<class I, class... A> void _replace( I, A&&... a )
+    template<class I, class... A> BOOST_CXX14_CONSTEXPR void _replace( I, A&&... a )
    {
        ::new( &storage( 0 ) ) variant_storage<none, T...>( mp11::mp_size_t<I::value + 1>(), std::forward<A>(a)... );
+
+        static_assert( ( I::value + 1 ) * 2 <= (std::numeric_limits<index_type>::max)(), "" );
        ix_ = ( I::value + 1 ) * 2;
    }

@@ -1155,19 +1209,19 @@ template<class... T> struct variant_base_impl<false, false, T...>
        variant_base_impl * this_;
        unsigned i2_;

-        template<class I> void operator()( I ) const noexcept
+        template<class I> BOOST_CXX14_CONSTEXPR void operator()( I ) const noexcept
        {
            using U = mp11::mp_at<mp11::mp_list<none, T...>, I>;
            this_->storage( i2_ ).get( I() ).~U();
        }
    };

-    void _destroy() noexcept
+    BOOST_CXX14_CONSTEXPR void _destroy() noexcept
    {
-        mp11::mp_with_index<1 + sizeof...(T)>( ix_ / 2, _destroy_L1{ this, ix_ & 1 } );
+        mp11::mp_with_index<1 + sizeof...(T)>( ix_ / 2, _destroy_L1{ this, static_cast<unsigned>( ix_ & 1 ) } );
    }

-    ~variant_base_impl() noexcept
+    BOOST_VARIANT2_CXX20_CONSTEXPR ~variant_base_impl() noexcept
    {
        _destroy();
    }
@@ -1181,7 +1235,7 @@ template<class... T> struct variant_base_impl<false, false, T...>
    {
        BOOST_ASSERT( index() == I );

-        size_t const J = I+1;
+        std::size_t const J = I+1;

        constexpr mp11::mp_size_t<J> j{};
        return storage( ix_ & 1 ).get( j );
@@ -1191,22 +1245,23 @@ template<class... T> struct variant_base_impl<false, false, T...>
    {
        BOOST_VARIANT2_CX14_ASSERT( index() == I )

-        // size_t const J = I+1;
+        // std::size_t const J = I+1;
        // constexpr mp_size_t<J> j{};

        return storage( ix_ & 1 ).get( mp11::mp_size_t<I+1>() );
    }

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

        unsigned i2 = 1 - ( ix_ & 1 );

        storage( i2 ).emplace( mp11::mp_size_t<J>(), std::forward<A>(a)... );
        _destroy();

-        ix_ = J * 2 + i2;
+        static_assert( J * 2 + 1 <= (std::numeric_limits<index_type>::max)(), "" );
+        ix_ = static_cast<index_type>( J * 2 + i2 );
    }

    static constexpr bool uses_double_storage() noexcept
@@ -1357,7 +1412,7 @@ private:
        variant_base * this_;
        variant_base const & r;

-        template<class I> void operator()( I i ) const
+        template<class I> BOOST_CXX14_CONSTEXPR void operator()( I i ) const
        {
            this_->_replace( i, r._get_impl( i ) );
        }
@@ -1365,7 +1420,7 @@ private:

 public:

-    variant_cc_base_impl( variant_cc_base_impl const& r )
+    BOOST_CXX14_CONSTEXPR variant_cc_base_impl( variant_cc_base_impl const& r )
        noexcept( mp11::mp_all<std::is_nothrow_copy_constructible<T>...>::value )
        : variant_base()
    {
@@ -1437,7 +1492,7 @@ private:
        variant_base * this_;
        variant_base const & r;

-        template<class I> void operator()( I i ) const
+        template<class I> BOOST_CXX14_CONSTEXPR void operator()( I i ) const
        {
            this_->template emplace<I::value>( r._get_impl( i ) );
        }
@@ -1511,7 +1566,7 @@ private:
        variant_base * this_;
        variant_base & r;

-        template<class I> void operator()( I i ) const
+        template<class I> BOOST_CXX14_CONSTEXPR void operator()( I i ) const
        {
            this_->_replace( i, std::move( r._get_impl( i ) ) );
        }
@@ -1519,7 +1574,7 @@ private:

 public:

-    variant_mc_base_impl( variant_mc_base_impl && r )
+    BOOST_CXX14_CONSTEXPR variant_mc_base_impl( variant_mc_base_impl && r )
        noexcept( mp11::mp_all<std::is_nothrow_move_constructible<T>...>::value )
    {
        mp11::mp_with_index<sizeof...(T)>( r.index(), L2{ this, r } );
@@ -1590,7 +1645,7 @@ private:
        variant_base * this_;
        variant_base & r;

-        template<class I> void operator()( I i ) const
+        template<class I> BOOST_CXX14_CONSTEXPR void operator()( I i ) const
        {
            this_->template emplace<I::value>( std::move( r._get_impl( i ) ) );
        }
@@ -1598,7 +1653,7 @@ private:

 public:

-    variant_ma_base_impl& operator=( variant_ma_base_impl && r )
+    BOOST_CXX14_CONSTEXPR variant_ma_base_impl& operator=( variant_ma_base_impl && r )
        noexcept( mp11::mp_all<std::is_nothrow_move_constructible<T>...>::value )
    {
        mp11::mp_with_index<sizeof...(T)>( r.index(), L4{ this, r } );
@@ -1633,7 +1688,17 @@ public:
    template<class U,
        class Ud = typename std::decay<U>::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 )
@@ -1734,7 +1799,7 @@ private:
        variant * this_;
        variant & r;

-        template<class I> void operator()( I i ) const
+        template<class I> BOOST_CXX14_CONSTEXPR void operator()( I i ) const
        {
            using std::swap;
            swap( this_->_get_impl( i ), r._get_impl( i ) );
@@ -1743,7 +1808,7 @@ private:

 public:

-    void swap( variant& r ) noexcept( mp11::mp_all<std::is_nothrow_move_constructible<T>..., detail::is_nothrow_swappable<T>...>::value )
+    BOOST_CXX14_CONSTEXPR void swap( variant& r ) noexcept( mp11::mp_all<std::is_nothrow_move_constructible<T>..., detail::is_nothrow_swappable<T>...>::value )
    {
        if( index() == r.index() )
        {
@@ -1770,7 +1835,7 @@ private:
        variant_base * this_;
        variant<U...> const & r;

-        template<class I> void operator()( I i ) const
+        template<class I> BOOST_CXX14_CONSTEXPR void operator()( I i ) const
        {
            using J = mp11::mp_find<mp11::mp_list<T...>, mp11::mp_at<mp11::mp_list<U...>, I>>;
            this_->_replace( J{}, r._get_impl( i ) );
@@ -1781,7 +1846,7 @@ public:

    template<class... U,
        class E2 = mp11::mp_if<mp11::mp_all<std::is_copy_constructible<U>..., mp11::mp_contains<mp11::mp_list<T...>, U>...>, void> >
-    variant( variant<U...> const& r )
+    BOOST_CXX14_CONSTEXPR variant( variant<U...> const& r )
        noexcept( mp11::mp_all<std::is_nothrow_copy_constructible<U>...>::value )
    {
        mp11::mp_with_index<sizeof...(U)>( r.index(), L6<U...>{ this, r } );
@@ -1794,7 +1859,7 @@ private:
        variant_base * this_;
        variant<U...> & r;

-        template<class I> void operator()( I i ) const
+        template<class I> BOOST_CXX14_CONSTEXPR void operator()( I i ) const
        {
            using J = mp11::mp_find<mp11::mp_list<T...>, mp11::mp_at<mp11::mp_list<U...>, I>>;
            this_->_replace( J{}, std::move( r._get_impl( i ) ) );
@@ -1805,7 +1870,7 @@ public:

    template<class... U,
        class E2 = mp11::mp_if<mp11::mp_all<std::is_move_constructible<U>..., mp11::mp_contains<mp11::mp_list<T...>, U>...>, void> >
-    variant( variant<U...> && r )
+    BOOST_CXX14_CONSTEXPR variant( variant<U...> && r )
        noexcept( mp11::mp_all<std::is_nothrow_move_constructible<U>...>::value )
    {
        mp11::mp_with_index<sizeof...(U)>( r.index(), L7<U...>{ this, r } );
@@ -1831,7 +1896,7 @@ private:
    {
        variant * this_;

-        template<class I> variant<U...> operator()( I i ) const
+        template<class I> BOOST_CXX14_CONSTEXPR variant<U...> operator()( I i ) const
        {
            using J = mp11::mp_find<mp11::mp_list<U...>, mp11::mp_at<mp11::mp_list<T...>, I>>;
            return this_->_subset_impl<U...>( J{}, this_->_get_impl( i ) );
@@ -1853,7 +1918,7 @@ private:
    {
        variant const * this_;

-        template<class I> variant<U...> operator()( I i ) const
+        template<class I> BOOST_CXX14_CONSTEXPR variant<U...> operator()( I i ) const
        {
            using J = mp11::mp_find<mp11::mp_list<U...>, mp11::mp_at<mp11::mp_list<T...>, I>>;
            return this_->_subset_impl<U...>( J{}, this_->_get_impl( i ) );
@@ -1875,7 +1940,7 @@ private:
    {
        variant * this_;

-        template<class I> variant<U...> operator()( I i ) const
+        template<class I> BOOST_CXX14_CONSTEXPR variant<U...> operator()( I i ) const
        {
            using J = mp11::mp_find<mp11::mp_list<U...>, mp11::mp_at<mp11::mp_list<T...>, I>>;
            return this_->_subset_impl<U...>( J{}, std::move( this_->_get_impl( i ) ) );
@@ -1901,7 +1966,7 @@ private:
    {
        variant const * this_;

-        template<class I> variant<U...> operator()( I i ) const
+        template<class I> BOOST_CXX14_CONSTEXPR variant<U...> operator()( I i ) const
        {
            using J = mp11::mp_find<mp11::mp_list<U...>, mp11::mp_at<mp11::mp_list<T...>, I>>;
            return this_->_subset_impl<U...>( J{}, std::move( this_->_get_impl( i ) ) );
@@ -2114,7 +2179,7 @@ template<class R, class F, class V1> struct visit_L1
    F&& f;
    V1&& v1;

-    template<class I> auto operator()( I ) const -> Vret<R, F, V1>
+    template<class I> constexpr auto operator()( I ) const -> Vret<R, F, V1>
    {
        return std::forward<F>(f)( unsafe_get<I::value>( std::forward<V1>(v1) ) );
    }
@@ -2237,7 +2302,7 @@ template<class R = detail::deduced, class F, class V1, class V2, class... V> con
 // specialized algorithms
 template<class... T,
    class E = typename std::enable_if<mp11::mp_all<std::is_move_constructible<T>..., detail::is_swappable<T>...>::value>::type>
-void swap( variant<T...> & v, variant<T...> & w )
+BOOST_CXX14_CONSTEXPR void swap( variant<T...> & v, variant<T...> & w )
    noexcept( noexcept(v.swap(w)) )
 {
    v.swap( w );
@@ -2319,8 +2384,8 @@ namespace detail

 inline std::size_t hash_value_impl_( mp11::mp_true, std::size_t index, std::size_t value )
 {
-    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;
+    unsigned long long hv = 0xCBF29CE484222325ull;
+    unsigned long long const prime = 0x100000001B3ull;

    hv ^= index;
    hv *= prime;
@@ -2497,16 +2562,16 @@ 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
+    template<class I> void operator()( I /*i*/ ) const
    {
        if( !r )
        {
-            using Ti = mp11::mp_at_c<V, i>;
+            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>{}, std::move( *r2 ) );
+                r.emplace( in_place_index_t<I::value>{}, std::move( *r2 ) );
            }
        }
    }
--- a/test/Jamfile
+++ b/test/Jamfile
@@ -7,7 +7,8 @@
 #  http://www.boost.org/LICENSE_1_0.txt

 import testing ;
-import ../../config/checks/config : requires ;
+import-search /boost/config/checks ;
+import config : requires ;

 project
  : default-build
@@ -16,11 +17,14 @@ project

  : requirements

-    [ requires cxx11_variadic_templates cxx11_template_aliases cxx11_decltype cxx11_constexpr ]
+    <library>/boost/variant2//boost_variant2
+    <library>/boost/core//boost_core
+    <library>/boost/container_hash//boost_container_hash

    <toolset>msvc:<warnings-as-errors>on
    <toolset>gcc:<warnings-as-errors>on
    <toolset>clang:<warnings-as-errors>on
+
  ;

 run quick.cpp ;
@@ -56,10 +60,10 @@ run variant_in_place_type_construct.cpp ;
 compile variant_in_place_type_construct_cx.cpp : <toolset>msvc-14.0:<build>no ;

 run variant_copy_assign.cpp ;
-compile variant_copy_assign_cx.cpp : [ requires cxx14_constexpr ] ;
+compile variant_copy_assign_cx.cpp : [ requires cxx14_constexpr ] <toolset>gcc-5:<build>no <toolset>gcc-6:<build>no ;

 run variant_move_assign.cpp ;
-compile variant_move_assign_cx.cpp : [ requires cxx14_constexpr ] ;
+compile variant_move_assign_cx.cpp : [ requires cxx14_constexpr ] <toolset>gcc-5:<build>no <toolset>gcc-6:<build>no ;

 run variant_value_assign.cpp ;
 compile variant_value_assign_cx.cpp : [ requires cxx14_constexpr ] ;
@@ -127,9 +131,38 @@ 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" ;
+local JSON = <library>/boost/json//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 ;
+
+compile variant_visit_cx.cpp : [ requires cxx14_constexpr ] ;
+compile variant_visit_cx_2.cpp : [ requires cxx14_constexpr ] ;
+compile variant_visit_r_cx.cpp : [ requires cxx14_constexpr ] ;
+
+local index-type-reqs =
+
+  <variant>release
+  <toolset>msvc,<address-model>32:<build>no
+  <toolset>clang,<target-os>linux:<cxxflags>-ftemplate-depth=1024 # for Clang 3.x
+;
+
+local list-sizes = 126 127 128 129 254 255 256 257 ;
+
+for local list-size in $(list-sizes)
+{
+    run variant_index_type.cpp : : : $(index-type-reqs) <define>LIST_SIZE=$(list-size) : variant_index_type_$(list-size) ;
+}
+
+compile variant_default_construct_cx_2.cpp ;
+compile variant_default_construct_cx_3.cpp ;
+compile variant_default_construct_cx_4.cpp ;
+compile variant_default_construct_cx_5.cpp ;
+
+compile variant_value_construct_cx_2.cpp ;
+compile variant_value_construct_cx_3.cpp ;
+compile variant_value_construct_cx_4.cpp ;
--- a/test/cmake_install_test/CMakeLists.txt
+++ b/test/cmake_install_test/CMakeLists.txt
@@ -14,4 +14,4 @@ target_link_libraries(quick Boost::variant2)
 enable_testing()
 add_test(quick quick)

-add_custom_target(check COMMAND ${CMAKE_CTEST_COMMAND} --output-on-failure -C $<CONFIG>)
+add_custom_target(check VERBATIM COMMAND ${CMAKE_CTEST_COMMAND} --output-on-failure -C $<CONFIG>)
--- a/test/cmake_subdir_test/CMakeLists.txt
+++ b/test/cmake_subdir_test/CMakeLists.txt
@@ -18,4 +18,4 @@ target_link_libraries(quick Boost::variant2)
 enable_testing()
 add_test(quick quick)

-add_custom_target(check COMMAND ${CMAKE_CTEST_COMMAND} --output-on-failure -C $<CONFIG>)
+add_custom_target(check VERBATIM COMMAND ${CMAKE_CTEST_COMMAND} --output-on-failure -C $<CONFIG>)
--- a/test/variant_copy_assign_throw.cpp
+++ b/test/variant_copy_assign_throw.cpp
@@ -45,7 +45,7 @@ void test()
    variant<Y1, Y2> v1( in_place_type_t<Y1>{} );
    variant<Y1, Y2> v2( in_place_type_t<Y2>{} );

-    BOOST_TEST_THROWS( v1 = v2, std::runtime_error )
+    BOOST_TEST_THROWS( v1 = v2, std::runtime_error );
 }

 int main()
--- a/test/variant_default_construct_cx_2.cpp
+++ b/test/variant_default_construct_cx_2.cpp
@@ -0,0 +1,32 @@
+// Copyright 2025 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/config/pragma_message.hpp>
+
+#if !defined(__cpp_constexpr_dynamic_alloc) || __cpp_constexpr_dynamic_alloc < 201907L
+
+BOOST_PRAGMA_MESSAGE("Skipping constexpr destructor test because __cpp_constexpr_dynamic_alloc < 201907L")
+int main() {}
+
+#else
+
+using namespace boost::variant2;
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+struct X
+{
+    constexpr ~X() {}
+};
+
+int main()
+{
+    constexpr variant<int, X> v;
+
+    STATIC_ASSERT( v.index() == 0 );
+    STATIC_ASSERT( get<0>(v) == 0 );
+}
+
+#endif
--- a/test/variant_default_construct_cx_3.cpp
+++ b/test/variant_default_construct_cx_3.cpp
@@ -0,0 +1,37 @@
+// Copyright 2025 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/config/pragma_message.hpp>
+
+#if !defined(__cpp_constexpr_dynamic_alloc) || __cpp_constexpr_dynamic_alloc < 201907L
+
+BOOST_PRAGMA_MESSAGE("Skipping constexpr destructor test because __cpp_constexpr_dynamic_alloc < 201907L")
+int main() {}
+
+#elif defined(BOOST_CLANG) && BOOST_CLANG_VERSION < 180000
+
+BOOST_PRAGMA_MESSAGE("Skipping constexpr destructor test because BOOST_CLANG_VERSION < 180000")
+int main() {}
+
+#else
+
+using namespace boost::variant2;
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+struct X
+{
+	~X() {}
+};
+
+int main()
+{
+    constexpr variant<int, X> v;
+
+    STATIC_ASSERT( v.index() == 0 );
+    STATIC_ASSERT( get<0>(v) == 0 );
+}
+
+#endif
--- a/test/variant_default_construct_cx_4.cpp
+++ b/test/variant_default_construct_cx_4.cpp
@@ -0,0 +1,33 @@
+// Copyright 2025 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/config/pragma_message.hpp>
+#include <string>
+
+#if !defined(__cpp_constexpr_dynamic_alloc) || __cpp_constexpr_dynamic_alloc < 201907L
+
+BOOST_PRAGMA_MESSAGE("Skipping constexpr destructor test because __cpp_constexpr_dynamic_alloc < 201907L")
+int main() {}
+
+#elif defined(BOOST_CLANG) && BOOST_CLANG_VERSION < 180000
+
+BOOST_PRAGMA_MESSAGE("Skipping constexpr destructor test because BOOST_CLANG_VERSION < 180000")
+int main() {}
+
+#else
+
+using namespace boost::variant2;
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+int main()
+{
+    constexpr variant<int, std::string> v;
+
+    STATIC_ASSERT( v.index() == 0 );
+    STATIC_ASSERT( get<0>(v) == 0 );
+}
+
+#endif
--- a/test/variant_default_construct_cx_5.cpp
+++ b/test/variant_default_construct_cx_5.cpp
@@ -0,0 +1,49 @@
+// Copyright 2025 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/config/pragma_message.hpp>
+
+#if !defined(__cpp_constexpr_dynamic_alloc) || __cpp_constexpr_dynamic_alloc < 201907L
+
+BOOST_PRAGMA_MESSAGE("Skipping constexpr destructor test because __cpp_constexpr_dynamic_alloc < 201907L")
+int main() {}
+
+#elif defined(BOOST_MSVC) && BOOST_MSVC < 1950
+
+BOOST_PRAGMA_MESSAGE("Skipping constexpr destructor test because BOOST_MSVC < 1950")
+int main() {}
+
+#elif defined(BOOST_CLANG) && BOOST_CLANG_VERSION < 180000
+
+BOOST_PRAGMA_MESSAGE("Skipping constexpr destructor test because BOOST_CLANG_VERSION < 180000")
+int main() {}
+
+#else
+
+using namespace boost::variant2;
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+struct X
+{
+};
+
+struct Y
+{
+    constexpr ~Y() {}
+};
+
+struct Z
+{
+    ~Z() {}
+};
+
+int main()
+{
+    constexpr variant<X, Y, Z> v;
+    STATIC_ASSERT( v.index() == 0 );
+}
+
+#endif
--- 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_index_type.cpp
+++ b/test/variant_index_type.cpp
@@ -0,0 +1,86 @@
+// Copyright 2024 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#if defined(_MSC_VER)
+# pragma warning( disable: 4503 ) // decorated name length exceeded
+#endif
+
+#include <boost/variant2/variant.hpp>
+#include <boost/mp11.hpp>
+#include <boost/core/lightweight_test.hpp>
+
+using namespace boost::mp11;
+
+template<std::size_t I> struct X
+{
+};
+
+template<class N> using Xf = X< N::value >;
+
+template<std::size_t I> struct Y
+{
+    Y() = default;
+    Y( Y&& ) {}
+};
+
+template<class N> using Yf = Y< N::value >;
+
+template<std::size_t I> struct Z
+{
+    ~Z() {}
+};
+
+template<class N> using Zf = Z< N::value >;
+
+template<std::size_t I> struct W
+{
+    ~W() {}
+
+    W() = default;
+    W( W&& ) {}
+};
+
+template<class N> using Wf = W< N::value >;
+
+template<class L, template<class...> class F> void test()
+{
+    using V = mp_rename< mp_transform<F, L>, boost::variant2::variant >;
+
+    constexpr std::size_t N = mp_size<L>::value;
+
+    using last_type = F<mp_size_t<N-1>>;
+
+    {
+        V v( last_type{} );
+        BOOST_TEST_EQ( v.index(), N-1 );
+    }
+
+    {
+        V v;
+        BOOST_TEST_EQ( v.index(), 0 );
+
+        v.template emplace<last_type>();
+        BOOST_TEST_EQ( v.index(), N-1 );
+    }
+}
+
+int main()
+{
+    constexpr std::size_t N = LIST_SIZE;
+    using L = mp_iota_c<N>;
+
+    static_assert( !boost::variant2::variant< X<0>, X<1> >::uses_double_storage(), "" );
+    test<L, Xf>();
+
+    static_assert( boost::variant2::variant< Y<0>, Y<1> >::uses_double_storage(), "" );
+    test<L, Yf>();
+
+    static_assert( !boost::variant2::variant< Z<0>, Z<1> >::uses_double_storage(), "" );
+    test<L, Zf>();
+
+    static_assert( boost::variant2::variant< W<0>, W<1> >::uses_double_storage(), "" );
+    test<L, Wf>();
+
+    return boost::report_errors();
+}
--- a/test/variant_json_value_from.cpp
+++ b/test/variant_json_value_from.cpp
@@ -2,6 +2,12 @@
 // Distributed under the Boost Software License, Version 1.0.
 // https://www.boost.org/LICENSE_1_0.txt

+#include <boost/config.hpp>
+
+#if defined(BOOST_GCC) && BOOST_GCC < 50000
+# define BOOST_ALLOW_DEPRECATED
+#endif
+
 #include <boost/variant2/variant.hpp>
 #include <boost/json/value_from.hpp>
 #include <boost/json/serialize.hpp>
--- a/test/variant_json_value_to.cpp
+++ b/test/variant_json_value_to.cpp
@@ -2,6 +2,12 @@
 // Distributed under the Boost Software License, Version 1.0.
 // https://www.boost.org/LICENSE_1_0.txt

+#include <boost/config.hpp>
+
+#if defined(BOOST_GCC) && BOOST_GCC < 50000
+# define BOOST_ALLOW_DEPRECATED
+#endif
+
 #include <boost/variant2/variant.hpp>
 #include <boost/json/value_to.hpp>
 #include <boost/json/serialize.hpp>
--- a/test/variant_move_assign_throw.cpp
+++ b/test/variant_move_assign_throw.cpp
@@ -45,7 +45,7 @@ void test()
    variant<Y1, Y2> v1( in_place_type_t<Y1>{} );
    variant<Y1, Y2> v2( in_place_type_t<Y2>{} );

-    BOOST_TEST_THROWS( v1 = std::move( v2 ), std::runtime_error )
+    BOOST_TEST_THROWS( v1 = std::move( v2 ), std::runtime_error );
 }

 int main()
--- a/test/variant_value_construct_cx_2.cpp
+++ b/test/variant_value_construct_cx_2.cpp
@@ -0,0 +1,32 @@
+// Copyright 2025 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/config/pragma_message.hpp>
+
+#if !defined(__cpp_constexpr_dynamic_alloc) || __cpp_constexpr_dynamic_alloc < 201907L
+
+BOOST_PRAGMA_MESSAGE("Skipping test because __cpp_constexpr_dynamic_alloc < 201907L")
+int main() {}
+
+#else
+
+using namespace boost::variant2;
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+struct X
+{
+    constexpr ~X() {}
+};
+
+int main()
+{
+    constexpr variant<X, int> v( 5 );
+
+    STATIC_ASSERT( v.index() == 1 );
+    STATIC_ASSERT( get<1>(v) == 5 );
+}
+
+#endif
--- a/test/variant_value_construct_cx_3.cpp
+++ b/test/variant_value_construct_cx_3.cpp
@@ -0,0 +1,37 @@
+// Copyright 2025 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/config/pragma_message.hpp>
+
+#if !defined(__cpp_constexpr_dynamic_alloc) || __cpp_constexpr_dynamic_alloc < 201907L
+
+BOOST_PRAGMA_MESSAGE("Skipping test because __cpp_constexpr_dynamic_alloc < 201907L")
+int main() {}
+
+#elif defined(BOOST_CLANG) && BOOST_CLANG_VERSION < 180000
+
+BOOST_PRAGMA_MESSAGE("Skipping test because BOOST_CLANG_VERSION < 180000")
+int main() {}
+
+#else
+
+using namespace boost::variant2;
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+struct X
+{
+	~X() {}
+};
+
+int main()
+{
+    constexpr variant<X, int> v( 5 );
+
+    STATIC_ASSERT( v.index() == 1 );
+    STATIC_ASSERT( get<1>(v) == 5 );
+}
+
+#endif
--- a/test/variant_value_construct_cx_4.cpp
+++ b/test/variant_value_construct_cx_4.cpp
@@ -0,0 +1,56 @@
+// Copyright 2025 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/config/pragma_message.hpp>
+
+#if !defined(__cpp_constexpr_dynamic_alloc) || __cpp_constexpr_dynamic_alloc < 201907L
+
+BOOST_PRAGMA_MESSAGE("Skipping test because __cpp_constexpr_dynamic_alloc < 201907L")
+int main() {}
+
+#elif defined(BOOST_MSVC) && BOOST_MSVC < 1950
+
+BOOST_PRAGMA_MESSAGE("Skipping test because BOOST_MSVC < 1950")
+int main() {}
+
+#elif defined(BOOST_CLANG) && BOOST_CLANG_VERSION < 180000
+
+BOOST_PRAGMA_MESSAGE("Skipping test because BOOST_CLANG_VERSION < 180000")
+int main() {}
+
+#else
+
+using namespace boost::variant2;
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+struct X
+{
+};
+
+struct Y
+{
+    constexpr ~Y() {}
+};
+
+struct Z
+{
+    ~Z() {}
+};
+
+int main()
+{
+    {
+        constexpr variant<X, Y, Z> v( X{} );
+        STATIC_ASSERT( v.index() == 0 );
+    }
+
+    {
+        constexpr variant<X, Y, Z> v( Y{} );
+        STATIC_ASSERT( v.index() == 1 );
+    }
+}
+
+#endif
--- a/test/variant_visit_cx.cpp
+++ b/test/variant_visit_cx.cpp
@@ -0,0 +1,51 @@
+// Copyright 2017, 2024 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// http://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/variant2/variant.hpp>
+using namespace boost::variant2;
+
+#if !defined(BOOST_MP11_HAS_CXX14_CONSTEXPR)
+
+#include <boost/config/pragma_message.hpp>
+
+BOOST_PRAGMA_MESSAGE("Skipping constexpr visit test because BOOST_MP11_HAS_CXX14_CONSTEXPR is not defined")
+
+int main() {}
+
+#else
+
+struct X
+{
+    constexpr operator int() const { return 2; }
+};
+
+struct F
+{
+    constexpr int operator()( int x ) const
+    {
+        return x;
+    }
+};
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+int main()
+{
+    {
+        constexpr variant<int> v( 1 );
+        STATIC_ASSERT( visit( F(), v ) == 1 );
+    }
+
+    {
+        constexpr variant<char, int> v( 'a' );
+        STATIC_ASSERT( visit( F(), v ) == 'a' );
+    }
+
+    {
+        constexpr variant<char, int, X> v( X{} );
+        STATIC_ASSERT( visit( F(), v ) == 2 );
+    }
+}
+
+#endif
--- a/test/variant_visit_cx_2.cpp
+++ b/test/variant_visit_cx_2.cpp
@@ -0,0 +1,53 @@
+// Copyright 2017, 2024 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// http://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/variant2/variant.hpp>
+#include <boost/config/pragma_message.hpp>
+
+#if !( defined(__cpp_constexpr) && __cpp_constexpr >= 201603L )
+
+BOOST_PRAGMA_MESSAGE("Skipping constexpr visit test because __cpp_constexpr < 201603L")
+int main() {}
+
+#elif !defined(BOOST_MP11_HAS_CXX14_CONSTEXPR)
+
+BOOST_PRAGMA_MESSAGE("Skipping constexpr visit test because BOOST_MP11_HAS_CXX14_CONSTEXPR is not defined")
+int main() {}
+
+#else
+
+using namespace boost::variant2;
+
+struct F
+{
+    constexpr int operator()( int x1, int x2 ) const
+    {
+        return x1 + x2;
+    }
+
+    constexpr int operator()( int x1, int x2, int x3 ) const
+    {
+        return x1 + x2 + x3;
+    }
+};
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+int main()
+{
+    {
+        constexpr variant<char, int> v1( 1 );
+        constexpr variant<char, int> v2( '2' );
+        STATIC_ASSERT( visit( F(), v1, v2 ) == 1 + '2' );
+    }
+
+    {
+        constexpr variant<char, int> v1( 1 );
+        constexpr variant<char, int> v2( 2 );
+        constexpr variant<char, int> v3( '3' );
+        STATIC_ASSERT( visit( F(), v1, v2, v3 ) == 1 + 2 + '3' );
+    }
+}
+
+#endif
--- a/test/variant_visit_r_cx.cpp
+++ b/test/variant_visit_r_cx.cpp
@@ -0,0 +1,52 @@
+// Copyright 2017, 2024 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// http://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/variant2/variant.hpp>
+using namespace boost::variant2;
+
+#if !defined(BOOST_MP11_HAS_CXX14_CONSTEXPR)
+
+#include <boost/config/pragma_message.hpp>
+
+BOOST_PRAGMA_MESSAGE("Skipping constexpr visit test because BOOST_MP11_HAS_CXX14_CONSTEXPR is not defined")
+
+int main() {}
+
+#else
+
+struct X
+{
+    int v;
+    constexpr operator int() const { return v; }
+};
+
+struct F
+{
+    template<class T> constexpr T operator()( T x ) const
+    {
+        return x;
+    }
+};
+
+#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
+
+int main()
+{
+    {
+        constexpr variant<int> v( 1 );
+        STATIC_ASSERT( visit<int>( F(), v ) == 1 );
+    }
+
+    {
+        constexpr variant<char, int> v( 'a' );
+        STATIC_ASSERT( visit<int>( F(), v ) == 'a' );
+    }
+
+    {
+        constexpr variant<char, int, X> v( X{2} );
+        STATIC_ASSERT( visit<int>( F(), v ) == 2 );
+    }
+}
+
+#endif
Author	SHA1	Message	Date
Peter Dimov	f267609ad6	Update revision history	2025-10-22 21:03:21 +03:00
Peter Dimov	edf1c7925b	Correct CMake version check; VERSION_GREATER 3.18 is true for 3.18.1	2025-10-19 21:07:20 +03:00
Peter Dimov	b9d0499a8f	BOOST_TEST_THROWS requires a semicolon after https://github.com/boostorg/core/pull/205	2025-10-18 20:23:49 +03:00
Peter Dimov	a63b03286e	Add test/variant_value_construct_cx_2, 3, 4. Refs #53 .	2025-10-18 08:24:39 +03:00
Peter Dimov	5661f2ba15	Disable variant_default_construct_cx_4, _5 on Clang < 18 as well	2025-10-18 03:12:52 +03:00
Peter Dimov	9d913eb1a0	Disable variant_default_construct_cx_3 on Clang < 18; earlier versions complain that the type isn't literal.	2025-10-18 03:01:19 +03:00
Peter Dimov	43377dcada	Add test/variant_default_construct_cx_5. Refs #53 .	2025-10-18 02:49:29 +03:00
Peter Dimov	2af2d02fce	Add test/variant_default_construct_cx_4. Refs #53 .	2025-10-18 02:41:28 +03:00
Peter Dimov	b2109dee2a	Add test/variant_default_construct_cx_3. Refs #53 .	2025-10-18 02:37:21 +03:00
Peter Dimov	df001efb54	Add test/variant_default_construct_cx_2. Refs #53 .	2025-10-18 02:29:52 +03:00
Peter Dimov	e708866c65	Add more constexpr. Refs #53 .	2025-10-17 22:24:26 +03:00
Peter Dimov	28d23c14f6	Update ci.yml	2025-10-17 21:21:02 +03:00
Peter Dimov	8caa1a3484	Update revision history	2025-01-15 19:44:18 +02:00
Peter Dimov	6669e07071	Work around GCC 5, 6 failures	2024-12-22 20:12:08 +02:00
Peter Dimov	df84f1f146	Work around Clang 3.x failures	2024-12-22 20:10:16 +02:00
Peter Dimov	2630b3e572	Use the smallest appropriate unsigned type for the index. Closes #50 .	2024-12-22 19:09:05 +02:00
Peter Dimov	010c78598e	Split variant_index_type into separate runs for each variant size	2024-12-22 06:03:10 +02:00
Peter Dimov	d77d61c8ec	Avoid use of mp_back in variant_index_type.cpp	2024-12-22 04:52:07 +02:00
Peter Dimov	8f6918554e	Use -j2 on GHA and Appveyor to avoid MSVC out of heap errors	2024-12-22 04:31:47 +02:00
Peter Dimov	183aea23a9	Only use -ftemplate-depth for Clang on Linux, because clang-cl doesn't like it (and Mac doesn't need it)	2024-12-22 03:20:39 +02:00
Peter Dimov	7c64abd41c	Remove clang-5.0/cxxstd=1z from Drone as well	2024-12-22 03:16:12 +02:00
Peter Dimov	7b8e8c33bb	Disable variant_index_type.cpp for msvc-14.0, because GHA fails with 'out of heap space'	2024-12-22 03:09:28 +02:00
Peter Dimov	2f5dbc19b5	Remove cxxstd=1z for Clang 5.0	2024-12-22 03:03:57 +02:00
Peter Dimov	639bd0232b	Add -ftemplate-depth=1024 for Clang (3.x needs it)	2024-12-22 03:03:35 +02:00
Peter Dimov	94749d088d	Disable variant_index_type.cpp for MSVC 32 bit	2024-12-22 02:44:02 +02:00
Peter Dimov	e2fc107ac7	Add test/variant_index_type.cpp. Refs #50 .	2024-12-21 20:15:45 +02:00
Peter Dimov	306a602d19	Compute the index type with a metafunction. Refs #50 .	2024-12-21 19:01:18 +02:00
Peter Dimov	509ce1dc77	Merge pull request #49 from Lastique/patch-1 Add missing std namespace qualifiers	2024-12-18 06:55:12 +02:00
Andrey Semashev	47e544959f	Added missing std namespace qualifiers.	2024-12-18 02:57:01 +03:00
Peter Dimov	8333e9af93	Apply Node20 workaround	2024-12-12 19:50:00 +02:00
Peter Dimov	19b75fffe4	Add test/variant_visit_cx_2.cpp. Refs #47 .	2024-11-23 04:11:30 +02:00
Peter Dimov	bdc1098c80	Add test/variant_visit_r_cx.cpp. Refs #47 .	2024-11-23 03:38:27 +02:00
Peter Dimov	9061e427c2	Add test/variant_visit_cx.cpp. Refs #47 .	2024-11-23 03:13:28 +02:00
Peter Dimov	1202390861	Update .drone.jsonnet	2024-11-22 23:06:34 +02:00
Peter Dimov	79061e470f	Update ci.yml	2024-11-22 22:53:17 +02:00
Peter Dimov	a4b167b723	Add VERBATIM to add_custom_target	2024-08-28 20:45:54 +03:00
Peter Dimov	c7c5eb2510	Update .drone.jsonnet	2024-08-28 20:45:27 +03:00
Peter Dimov	acf24454d8	Update build.jam, test/Jamfile	2024-08-28 20:28:59 +03:00
Rene Rivera	f78343e18d	Sync from upstream.	2024-07-25 17:19:46 -05:00
Rene Rivera	ea4394914c	Move inter-lib dependencies to a project variable and into the build targets.	2024-07-23 22:34:24 -05:00
Peter Dimov	f5cd36af3d	Update MSVC workaround	2024-07-21 22:55:40 +03:00
Peter Dimov	0e325dcf8d	Update ci.yml	2024-07-21 22:38:06 +03:00
Peter Dimov	e3cf721a23	Define BOOST_ALLOW_DEPRECATED in JSON tests for g++ 4.x	2024-07-21 22:20:27 +03:00
Peter Dimov	d4f0e57b36	Update .drone.jsonnet	2024-07-21 21:54:28 +03:00
Rene Rivera	f874a2cb1b	Update copyright dates.	2024-07-20 22:52:05 -05:00
Rene Rivera	fc088e7273	Change all <source> references to <library>.	2024-07-20 21:27:52 -05:00
Rene Rivera	4f207d7363	Bump B2 require to 5.2	2024-06-14 11:33:56 -05:00
Rene Rivera	429a82a52e	Sync from upstream.	2024-05-19 23:15:27 -05:00
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
Rene Rivera	bb13b5be08	Add requires-b2 check to top-level build file.	2024-05-05 09:00:01 -05:00
Rene Rivera	1324e32b33	Add missing import-search for cconfig/predef checks.	2024-05-04 23:33:36 -05:00
Rene Rivera	02303d662e	Sync from upstream.	2024-04-10 07:58:16 -05:00
Rene Rivera	09f3802347	Switch to library requirements instead of source. As source puts extra source in install targets.	2024-03-29 21:16:00 -05:00
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
Rene Rivera	5c34125b14	Make the library modular usable.	2024-03-11 08:38:17 -05:00
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