EXP: [C++] Require C++20

Author: pitrou

.github/workflows/cpp.yml

@@ -290,7 +290,7 @@ jobs:
         include:
           - os: windows-2022
             simd-level: AVX2
-            title: AMD64 Windows 2022 AVX2
+            title: AMD64 Windows 2022 C++20 AVX2
     env:
       ARROW_BOOST_USE_SHARED: OFF
       ARROW_BUILD_BENCHMARKS: ON
@@ -317,7 +317,7 @@ jobs:
       ARROW_WITH_ZLIB: ON
       ARROW_WITH_ZSTD: ON
       BOOST_SOURCE: BUNDLED
-      CMAKE_CXX_STANDARD: "17"
+      CMAKE_CXX_STANDARD: "20"
       CMAKE_GENERATOR: Ninja
       CMAKE_INSTALL_LIBDIR: bin
       CMAKE_INSTALL_PREFIX: /usr

.github/workflows/r.yml

@@ -286,12 +286,13 @@ jobs:
           # static library. The R is not used here but R 4.1 was the last R to use
           # Rtools40.
           r-version: "4.1"
-          rtools-version: 40
+          rtools-version: ${{ matrix.config.rtools }}
           Ncpus: 2
       - name: Build Arrow C++
         shell: bash
         env:
           MINGW_ARCH: ${{ matrix.config.arch }}
+          RTOOLS_VERSION: ${{ matrix.config.rtools }}
         run: ci/scripts/r_windows_build.sh
       - name: Rename libarrow.zip
         # So that they're unique when multiple are downloaded in the next step

.github/workflows/ruby.yml

@@ -349,7 +349,7 @@ jobs:
       ARROW_WITH_SNAPPY: ON
       ARROW_WITH_ZLIB: ON
       ARROW_WITH_ZSTD: ON
-      CMAKE_CXX_STANDARD: "17"
+      CMAKE_CXX_STANDARD: "20"
       CMAKE_GENERATOR: Ninja
       CMAKE_INSTALL_PREFIX: "${{ github.workspace }}/dist"
       VCPKG_BINARY_SOURCES: 'clear;nuget,GitHub,readwrite'

c_glib/meson.build

@@ -21,7 +21,7 @@ project(
     'arrow-glib',
     'c',
     'cpp',
-    default_options: ['c_std=c99', 'cpp_std=c++17'],
+    default_options: ['c_std=c99', 'cpp_std=c++20'],
     license: 'Apache-2.0',
     # Debian:
     #   https://packages.debian.org/search?keywords=meson

ci/appveyor-cpp-build.bat

@@ -93,7 +93,7 @@ cmake -G "%GENERATOR%" %ARROW_CMAKE_ARGS% ^
       -DARROW_WITH_ZSTD=ON ^
       -DCMAKE_BUILD_TYPE="Release" ^
       -DCMAKE_CXX_FLAGS_RELEASE="/MD /Od /UNDEBUG" ^
-      -DCMAKE_CXX_STANDARD=17 ^
+      -DCMAKE_CXX_STANDARD=20 ^
       -DCMAKE_INSTALL_PREFIX=%CONDA_PREFIX%\Library ^
       -DCMAKE_UNITY_BUILD=ON ^
       -DCMAKE_VERBOSE_MAKEFILE=OFF ^

ci/docker/centos-7-cpp.dockerfile

@@ -25,7 +25,7 @@ RUN sed -i \
       -e 's/mirror\.centos\.org/vault.centos.org/' \
       /etc/yum.repos.d/*.repo
 
-# devtoolset is required for C++17
+# devtoolset is required for C++20
 RUN \
   yum install -y \
     centos-release-scl \
@@ -38,7 +38,8 @@ RUN \
     /etc/yum.repos.d/CentOS-SCLo-scl*.repo && \
   yum install -y \
     curl \
-    devtoolset-8 \
+    devtoolset-11-gcc-c++ \
+    devtoolset-11-make \
     diffutils \
     gcc-c++ \
     libcurl-devel \

ci/scripts/cpp_build.sh

@@ -167,7 +167,7 @@ elif [ "${ARROW_EMSCRIPTEN:-OFF}" = "ON" ]; then
     -DCMAKE_VERBOSE_MAKEFILE=${CMAKE_VERBOSE_MAKEFILE:-OFF} \
     -DCMAKE_C_FLAGS="${CFLAGS:-}" \
     -DCMAKE_CXX_FLAGS="${CXXFLAGS:-}" \
-    -DCMAKE_CXX_STANDARD="${CMAKE_CXX_STANDARD:-17}" \
+    -DCMAKE_CXX_STANDARD="${CMAKE_CXX_STANDARD:-20}" \
     -DCMAKE_INSTALL_LIBDIR=${CMAKE_INSTALL_LIBDIR:-lib} \
     -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX:-${ARROW_HOME}} \
     -DCMAKE_UNITY_BUILD=${CMAKE_UNITY_BUILD:-OFF} \
@@ -255,7 +255,7 @@ else
     -DCMAKE_VERBOSE_MAKEFILE=${CMAKE_VERBOSE_MAKEFILE:-OFF} \
     -DCMAKE_C_FLAGS="${CFLAGS:-}" \
     -DCMAKE_CXX_FLAGS="${CXXFLAGS:-}" \
-    -DCMAKE_CXX_STANDARD="${CMAKE_CXX_STANDARD:-17}" \
+    -DCMAKE_CXX_STANDARD="${CMAKE_CXX_STANDARD:-20}" \
     -DCMAKE_INSTALL_LIBDIR=${CMAKE_INSTALL_LIBDIR:-lib} \
     -DCMAKE_INSTALL_PREFIX=${CMAKE_INSTALL_PREFIX:-${ARROW_HOME}} \
     -DCMAKE_UNITY_BUILD=${CMAKE_UNITY_BUILD:-OFF} \

ci/scripts/r_windows_build.sh

@@ -44,7 +44,7 @@ mv mingw* build
 cd build
 
 # This may vary by system/CI provider
-MSYS_LIB_DIR="/c/rtools40"
+MSYS_LIB_DIR="/c/rtools${RTOOLS_VERSION}"
 
 # Untar the builds we made
 ls *.xz | xargs -n 1 tar -xJf

cpp/CMakeLists.txt

@@ -625,10 +625,10 @@ set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${ARROW_CXXFLAGS}")
 # C++ specific flags.
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${CXX_COMMON_FLAGS} ${ARROW_CXXFLAGS}")
 
-# Remove --std=c++17 to avoid errors from C compilers
-string(REPLACE "-std=c++17" "" CMAKE_C_FLAGS ${CMAKE_C_FLAGS})
+# Remove -std=c++20 to avoid errors from C compilers
+string(REPLACE "-std=c++20" "" CMAKE_C_FLAGS ${CMAKE_C_FLAGS})
 
-# Add C++-only flags, like -std=c++17
+# Add C++-only flags, like -std=c++20
 set(CMAKE_CXX_FLAGS "${CXX_ONLY_FLAGS} ${CMAKE_CXX_FLAGS}")
 
 # ASAN / TSAN / UBSAN

cpp/cmake_modules/GandivaAddBitcode.cmake

@@ -17,7 +17,7 @@
 
 # Create bitcode for the given source file.
 function(gandiva_add_bitcode SOURCE)
-  set(CLANG_OPTIONS -std=c++17)
+  set(CLANG_OPTIONS -std=c++20)
   if(MSVC)
     # "19.20" means that it's compatible with Visual Studio 16 2019.
     # We can update this to "19.30" when we dropped support for Visual