Compile with C++20 instead of C++17 (facebook#953)

Summary: Pull Request resolved: facebook#953

Differential Revision: D79466725

Author: xuhdev

.github/actions/setup-build-and-test-w-make-impl/action.yml

@@ -29,11 +29,11 @@ runs:
   - name: Cache build
     uses: actions/cache@v4
     with:
-      key: v2-build-cache-${{ inputs.job_name }}.${{ inputs.setup_toolchain_extra }}.${{ inputs.configure_extra }}-${{ runner.arch }}-${{ github.ref_name }}-${{ github.sha }}
+      key: v3-build-cache-${{ inputs.job_name }}.${{ inputs.setup_toolchain_extra }}.${{ inputs.configure_extra }}-${{ runner.arch }}-${{ github.ref_name }}-${{ github.sha }}
       path: build.tar.zstd
       restore-keys: |
-        v2-build-cache-${{ inputs.job_name }}.${{ inputs.setup_toolchain_extra }}.${{ inputs.configure_extra }}-${{ runner.arch }}-${{ github.ref_name }}-
-        v2-build-cache-${{ inputs.job_name }}.${{ inputs.setup_toolchain_extra }}.${{ inputs.configure_extra }}-${{ runner.arch }}-${{ github.base_ref }}-
+        v3-build-cache-${{ inputs.job_name }}.${{ inputs.setup_toolchain_extra }}.${{ inputs.configure_extra }}-${{ runner.arch }}-${{ github.ref_name }}-
+        v3-build-cache-${{ inputs.job_name }}.${{ inputs.setup_toolchain_extra }}.${{ inputs.configure_extra }}-${{ runner.arch }}-${{ github.base_ref }}-
   # Would be nice to use the cache action output, but we want to unpack even on
   # restore_keys hit.
   - name: Unpack build cache

Makefile.am

@@ -18,6 +18,9 @@ DISABLED_WARNINGS_HARD = \
   -Wno-unknown-warning-option
 
 # TODO: Minimize this list.
+# TODO(T233149341): Narrow -Wno-volatile to problematic early verisons of
+# jsoncpp < 1.9.5 (https://github.com/open-source-parsers/jsoncpp/issues/1193).
+# This is currently only a problem on Debian 11.
 DISABLED_WARNINGS = \
   $(DISABLED_WARNINGS_HARD) \
   -Wno-array-bounds \
@@ -46,9 +49,10 @@ DISABLED_WARNINGS = \
   -Wno-unused-private-field \
   -Wno-unused-result \
   -Wno-unused-value \
-  -Wno-unused-variable
+  -Wno-unused-variable \
+  -Wno-volatile
 
-AM_CXXFLAGS = --std=gnu++17 -O3 -Wall -Werror -Wextra $(DISABLED_WARNINGS) -g1
+AM_CXXFLAGS = --std=gnu++20 -O3 -Wall -Werror -Wextra $(DISABLED_WARNINGS) -g1
 
 include $(top_srcdir)/Makefile.inc
 

cmake_modules/Commons.cmake

@@ -10,8 +10,8 @@ function(print_dirs var name)
 endfunction()
 
 macro(set_common_cxx_flags_for_redex)
-    message(STATUS "Using C++17")
-    set(CMAKE_CXX_STANDARD 17)
+    message(STATUS "Using C++20")
+    set(CMAKE_CXX_STANDARD 20)
     set(CMAKE_CXX_STANDARD_REQUIRED ON)
     set(CMAKE_CXX_EXTENSIONS OFF)
     if (MSVC)

configure.ac

@@ -7,7 +7,7 @@ AM_INIT_AUTOMAKE([subdir-objects])
 # clear out default cxx flags (was "-O2 -g") so that they don't override
 # the flags defined in AM_CXXFLAGS. add "-std" to work around gtest issue
 # on macos.
-: ${CXXFLAGS="-std=gnu++17"}
+: ${CXXFLAGS="-std=gnu++20"}
 
 # Checks for programs.
 AC_PROG_CXX
@@ -97,7 +97,7 @@ AS_IF([test "x$enable_protobuf" = "xyes"], [
             CXXFLAGS_ORIG=$CXXFLAGS
 
             # test protobuf header
-            CXXFLAGS="-std=gnu++17 ${CXXFLAGS_ORIG} -I${withval}"
+            CXXFLAGS="-std=gnu++20 ${CXXFLAGS_ORIG} -I${withval}"
             AC_LANG_PUSH([C++])
             AC_CHECK_HEADER([google/protobuf/io/coded_stream.h], [
                 # library found

setup_oss_toolchain.sh

@@ -66,12 +66,13 @@ function install_googletest_from_source {
     mkdir -p toolchain_install/gtest
     pushd toolchain_install/gtest
     tar xf "../../dl_cache/gtest/googletest-${GOOGLETEST_MIN_VERSION}.tar.gz" --no-same-owner --strip-components=1
-    # GoogleTest's string_view matcher requires compiler to support C++17. Older
-    # GCC versions need to be told to use C++17 with -std=gnu++17.
+    # GoogleTest's string_view matcher requires compiler to support C++17 or
+    # later. Older GCC versions need to be explicitly told to use a later C++
+    # standard.
     if [ "$BITNESS" = "32" ] ; then
-        CFLAGS=-m32 CXXFLAGS="-m32 -std=gnu++17" LDFLAGS=-m32 cmake .
+        CFLAGS=-m32 CXXFLAGS="-m32 -std=gnu++20" LDFLAGS=-m32 cmake .
     else
-        CXXFLAGS="-std=gnu++17" cmake .
+        CXXFLAGS="-std=gnu++20" cmake .
     fi
     cmake --build . --target install
     popd

test/integ/Makefile.am

@@ -6,7 +6,7 @@ DX = @DX@
 ANDROID_SDK = @ANDROID_SDK@
 ANDROID_PLATFORM_VERSION = @ANDROID_PLATFORM_VERSION@
 
-AM_CXXFLAGS = --std=gnu++17
+AM_CXXFLAGS = --std=gnu++20
 AM_CPPFLAGS = $(COMMON_INCLUDES) $(COMMON_TEST_INCLUDES)
 
 # Boost.

test/unit/Makefile.am

@@ -4,7 +4,7 @@ include $(top_srcdir)/test/Makefile.inc
 ANDROID_SDK = @ANDROID_SDK@
 ANDROID_PLATFORM_VERSION = @ANDROID_PLATFORM_VERSION@
 
-AM_CXXFLAGS = --std=gnu++17
+AM_CXXFLAGS = --std=gnu++20
 AM_CPPFLAGS = $(COMMON_INCLUDES) $(COMMON_TEST_INCLUDES)
 
 # Boost.