Switch from C++17 to C++20.

.bazelrc

@@ -1 +1 @@
-build --action_env=BAZEL_CXXOPTS="-std=c++17"
+build --action_env=BAZEL_CXXOPTS="-std=c++20"

.clang-format

@@ -20,7 +20,7 @@ IncludeBlocks: Regroup
 # Force pointers to the type for C++.
 DerivePointerAlignment: false
 PointerAlignment: Right
-Standard: c++17
+Standard: c++20
 IncludeCategories:
 # Matches common headers first and sorts them before project includes
 - Regex: '^<.+/.*\.h>'

CMakeLists.txt

@@ -23,8 +23,8 @@ endif()
 
 project (P4C)
 
-# set (CMAKE_CXX_EXTENSIONS OFF) # prefer using -std=c++17 rather than -std=gnu++17
-set (CMAKE_CXX_STANDARD 17)
+# set (CMAKE_CXX_EXTENSIONS OFF) # prefer using -std=c++20 rather than -std=gnu++20
+set (CMAKE_CXX_STANDARD 20)
 set (CMAKE_CXX_STANDARD_REQUIRED ON)
 
 set (CMAKE_MODULE_PATH ${PROJECT_SOURCE_DIR}/cmake)

bazel/example/.bazelrc

@@ -1 +1 @@
-build --action_env=BAZEL_CXXOPTS="-std=c++17"
+build --action_env=BAZEL_CXXOPTS="-std=c++20"

docs/C++.md

@@ -1,4 +1,4 @@
-C++ (following the C++ 11 standard) is the implementation language for
+C++ (following the C++ 20 standard) is the implementation language for
 the compiler.  This file contains notes on how we use C++ and conventions
 we use for things that C++ does not handle well.