Upgrade to C++23 (#507)

Use the same CXX standard as Drake itself uses.

Author: tyler-yankee

drake_bazel_download/.bazelrc

@@ -11,9 +11,9 @@ build --strip=never
 build --test_output=errors
 build --test_summary=terse
 
-# Use C++20.
-build --cxxopt=-std=c++20
-build --host_cxxopt=-std=c++20
+# Use C++23.
+build --cxxopt=-std=c++23
+build --host_cxxopt=-std=c++23
 
 # https://github.com/bazelbuild/bazel/issues/1164
 build --action_env=CCACHE_DISABLE=1

drake_bazel_external/.bazelrc

@@ -11,9 +11,9 @@ build --strip=never
 build --test_output=errors
 build --test_summary=terse
 
-# Use C++20.
-build --cxxopt=-std=c++20
-build --host_cxxopt=-std=c++20
+# Use C++23.
+build --cxxopt=-std=c++23
+build --host_cxxopt=-std=c++23
 
 # Suppress warnings from module externals.
 build --per_file_copt=external/.*@-w

drake_cmake_installed/CMakeLists.txt

@@ -26,7 +26,7 @@ get_filename_component(DRAKE_PYTHONPATH
 )
 
 set(CMAKE_CXX_EXTENSIONS OFF)
-set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_STANDARD 23)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_POSITION_INDEPENDENT_CODE ON)
 

drake_cmake_installed_apt/CMakeLists.txt

@@ -11,7 +11,7 @@ project(drake_cmake_installed_apt)
 include(CTest)
 
 set(CMAKE_CXX_EXTENSIONS OFF)
-set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_STANDARD 23)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_POSITION_INDEPENDENT_CODE ON)