Add test/variant_value_construct_cx_2, 3, 4. Refs #53.

Add missing std namespace qualifiers

.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 []) +
@@ -99,270 +101,298 @@ local windows_pipeline(name, image, environment, arch = "amd64") =
     linux_pipeline(
         "Linux 16.04 GCC 4.8 32/64",
         "cppalliance/droneubuntu1604:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '03,11', ADDRMD: '32,64' },
+        { TOOLSET: 'gcc', COMPILER: 'g++-4.8', CXXSTD: '11', ADDRMD: '32,64' },
         "g++-4.8-multilib",
     ),
 
     linux_pipeline(
         "Linux 16.04 GCC 4.9 32/64",
         "cppalliance/droneubuntu1604:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++-4.9', CXXSTD: '03,11', ADDRMD: '32,64' },
+        { TOOLSET: 'gcc', COMPILER: 'g++-4.9', CXXSTD: '11', ADDRMD: '32,64' },
         "g++-4.9-multilib",
     ),
 
     linux_pipeline(
         "Linux 16.04 GCC 5* 32/64",
         "cppalliance/droneubuntu1604:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++', CXXSTD: '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 32/64",
         "cppalliance/droneubuntu2204:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '03,11,14,17,20,2b', ADDRMD: '32,64' },
+        { TOOLSET: 'gcc', COMPILER: 'g++-12', CXXSTD: '11,14,17,20,2b', ADDRMD: '32,64' },
         "g++-12-multilib",
     ),
 
     linux_pipeline(
-        "Linux 23.04 GCC 13 32 ASAN",
-        "cppalliance/droneubuntu2304:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++-13', CXXSTD: '03,11,14,17,20,2b', ADDRMD: '32' } + asan,
+        "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 23.04 GCC 13 64 ASAN",
-        "cppalliance/droneubuntu2304:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++-13', CXXSTD: '03,11,14,17,20,2b', ADDRMD: '64' } + asan,
-        "g++-13-multilib",
+        "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 23.04 GCC 13 32 UBSAN",
-        "cppalliance/droneubuntu2304:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++-13', CXXSTD: '03,11,14,17,20,2b', ADDRMD: '32' } + ubsan,
-        "g++-13-multilib",
+        "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 23.04 GCC 13 64 UBSAN",
-        "cppalliance/droneubuntu2304:1",
-        { TOOLSET: 'gcc', COMPILER: 'g++-13', CXXSTD: '03,11,14,17,20,2b', ADDRMD: '64' } + ubsan,
-        "g++-13-multilib",
+        "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",
         "cppalliance/droneubuntu2204:1",
-        { TOOLSET: 'clang', COMPILER: 'clang++-15', CXXSTD: '03,11,14,17,20,2b' },
+        { TOOLSET: 'clang', COMPILER: 'clang++-15', CXXSTD: '11,14,17,20,2b' },
         "clang-15",
     ),
 
     linux_pipeline(
-        "Linux 23.04 Clang 16",
-        "cppalliance/droneubuntu2304:1",
-        { TOOLSET: 'clang', COMPILER: 'clang++-16', CXXSTD: '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 23.10 Clang 17 UBSAN",
-        "cppalliance/droneubuntu2310:1",
-        { TOOLSET: 'clang', COMPILER: 'clang++-17', CXXSTD: '03,11,14,17,20,2b' } + ubsan,
+        "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 23.10 Clang 17 ASAN",
-        "cppalliance/droneubuntu2310:1",
-        { TOOLSET: 'clang', COMPILER: 'clang++-17', CXXSTD: '03,11,14,17,20,2b' } + asan,
+        "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",
     ),
 

.github/workflows/ci.yml

@@ -18,161 +18,213 @@ jobs:
       matrix:
         include:
           - toolset: gcc-4.8
-            cxxstd: "03,11"
+            cxxstd: "11"
             container: ubuntu:16.04
             os: ubuntu-latest
             install: g++-4.8
           - toolset: gcc-4.9
-            cxxstd: "03,11"
+            cxxstd: "11"
             container: ubuntu:16.04
             os: ubuntu-latest
             install: g++-4.9
           - toolset: gcc-5
-            cxxstd: "03,11,14,1z"
+            cxxstd: "11,14,1z"
             container: ubuntu:18.04
             os: ubuntu-latest
             install: g++-5
           - toolset: gcc-6
-            cxxstd: "03,11,14,1z"
+            cxxstd: "11,14,1z"
             container: ubuntu:18.04
             os: ubuntu-latest
             install: g++-6
           - toolset: gcc-7
-            cxxstd: "03,11,14,17"
+            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: "03,11,14,17,20,2b"
-            container: ubuntu:23.04
+            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"
+            cxxstd: "11,14"
             container: ubuntu:18.04
             os: ubuntu-latest
             install: clang-3.9
           - toolset: clang
             compiler: clang++-4.0
-            cxxstd: "03,11,14"
+            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"
+            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"
+            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"
+            cxxstd: "11,14,17,20,2b"
             container: ubuntu:22.04
             os: ubuntu-latest
             install: clang-14
           - toolset: clang
             compiler: clang++-15
-            cxxstd: "03,11,14,17,20,2b"
+            cxxstd: "11,14,17,20,2b"
             container: ubuntu:22.04
             os: ubuntu-latest
             install: clang-15
           - toolset: clang
             compiler: clang++-16
-            cxxstd: "03,11,14,17,20,2b"
-            container: ubuntu:23.04
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:24.04
             os: ubuntu-latest
             install: clang-16
           - toolset: clang
             compiler: clang++-17
-            cxxstd: "03,11,14,17,20,2b"
-            container: ubuntu:23.10
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:24.04
             os: ubuntu-latest
             install: clang-17
           - toolset: clang
-            cxxstd: "03,11,14,17,2a"
-            os: macos-11
+            compiler: clang++-18
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:24.04
+            os: ubuntu-latest
+            install: clang-18
           - toolset: clang
-            cxxstd: "03,11,14,17,20,2b"
-            os: macos-12
+            compiler: clang++-19
+            cxxstd: "11,14,17,20,2b"
+            container: ubuntu:24.04
+            os: ubuntu-latest
+            install: clang-19
           - toolset: clang
-            cxxstd: "03,11,14,17,20,2b"
+            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 python3 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
@@ -217,14 +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
@@ -234,14 +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
@@ -269,23 +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: macos-12
+          - 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
@@ -324,16 +368,16 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: ubuntu-20.04
           - os: ubuntu-22.04
-          - os: macos-11
-          - os: macos-12
+          - 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
@@ -382,16 +426,16 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: ubuntu-20.04
           - os: ubuntu-22.04
-          - os: macos-11
-          - os: macos-12
+          - 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
@@ -438,13 +482,12 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: windows-2019
-          - os: windows-2022
+          - os: windows-latest
 
     runs-on: ${{matrix.os}}
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Setup Boost
         shell: cmd
@@ -487,13 +530,12 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: windows-2019
-          - os: windows-2022
+          - os: windows-latest
 
     runs-on: ${{matrix.os}}
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Setup Boost
         shell: cmd
@@ -554,13 +596,12 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - os: windows-2019
-          - os: windows-2022
+          - os: windows-latest
 
     runs-on: ${{matrix.os}}
 
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
 
       - name: Setup Boost
         shell: cmd

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 ..

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
+    ;

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 +8,10 @@ https://www.boost.org/LICENSE_1_0.txt
 # Revision History
 :idprefix: changelog_
 
+## Changes in 1.88.0
+
+* Use the smallest appropriate unsigned type for the index.
+
 ## Changes in 1.83.0
 
 * Added `uses_double_storage()`.

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={*($T41*)&amp;st_[ix_%2]} }}</DisplayString>
+    <Expand>
+      <Item Name="index">index()</Item>
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+      <Item Name="[value]" Condition="index() ==  1" Optional="true">*($T3*)&amp;st_[ix_%2]</Item>
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+      <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">*($T19*)&amp;st_[ix_%2]</Item>
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+      <Item Name="[value]" Condition="index() == 28" Optional="true">*($T30*)&amp;st_[ix_%2]</Item>
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+      <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>
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+      <Item Name="[value]" Condition="index() == 39" Optional="true">*($T41*)&amp;st_[ix_%2]</Item>
+    </Expand>
+  </Type>
 
 </AutoVisualizer>

include/boost/variant2/variant.hpp

@@ -26,6 +26,16 @@
 #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
 
 //
 
@@ -83,7 +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; }
@@ -556,16 +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)... );
     }
@@ -605,22 +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)... );
     }
@@ -673,7 +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)... );
     }
@@ -741,16 +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 )
     {
@@ -845,6 +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;
@@ -855,8 +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 )
     {
@@ -867,9 +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;
     }
 
@@ -880,7 +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 );
 
@@ -889,7 +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 )
 
@@ -901,6 +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;
     }
 
@@ -911,6 +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;
     }
 
@@ -931,8 +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 )
     {
@@ -943,9 +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;
     }
 
@@ -958,7 +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 );
@@ -968,7 +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>() );
@@ -976,13 +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
@@ -994,8 +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 )
     {
@@ -1006,9 +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;
     }
 
@@ -1021,14 +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 )
         {
@@ -1036,7 +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();
     }
@@ -1048,7 +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 );
 
@@ -1057,16 +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>;
 
@@ -1077,6 +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;
     }
 
@@ -1089,12 +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 )
     {
@@ -1117,7 +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 )
     {
@@ -1140,9 +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;
     }
 
@@ -1156,19 +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();
     }
@@ -1182,7 +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 );
@@ -1192,22 +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
@@ -1358,7 +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 ) );
         }
@@ -1366,7 +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()
     {
@@ -1438,7 +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 ) );
         }
@@ -1512,7 +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 ) ) );
         }
@@ -1520,7 +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 } );
@@ -1591,7 +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 ) ) );
         }
@@ -1599,7 +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 } );
@@ -1634,7 +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 )
@@ -1735,7 +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 ) );
@@ -1744,7 +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() )
         {
@@ -1771,7 +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 ) );
@@ -1782,7 +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 } );
@@ -1795,7 +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 ) ) );
@@ -1806,7 +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 } );
@@ -1832,7 +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 ) );
@@ -1854,7 +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 ) );
@@ -1876,7 +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 ) ) );
@@ -1902,7 +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 ) ) );
@@ -2115,7 +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) ) );
     }
@@ -2238,7 +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 );

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 ;

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>)

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>)

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

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

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

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

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();
+}

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();
+}

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>

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>

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

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

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

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

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

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