Promote "Upgrade C++ standard version from 17 to 20"

Makefile.am

@@ -18,6 +18,11 @@ 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.
+# TODO(T233149341): Narrow -Wno-restrict to problematic verisons of
+# GCC, i.e., 12: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105651
 DISABLED_WARNINGS = \
   $(DISABLED_WARNINGS_HARD) \
   -Wno-array-bounds \
@@ -32,6 +37,7 @@ DISABLED_WARNINGS = \
   -Wno-parentheses \
   -Wno-range-loop-analysis \
   -Wno-redundant-move \
+  -Wno-restrict \
   -Wno-return-type \
   -Wno-shift-count-overflow \
   -Wno-sign-compare \
@@ -46,9 +52,10 @@ 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

libredex/RedexResources.cpp

@@ -545,14 +545,12 @@ std::string convert_utf8_to_mutf8(std::string_view input) {
   return out.str();
 }
 
-#if __cplusplus >= 202002L
 std::string convert_utf8_to_mutf8(std::u8string_view input) {
   return convert_utf8_to_mutf8(std::string_view(
       // reinterpret_cast here is safe because the char8_t has the same size and
       // alignment with char.
       reinterpret_cast<const char*>(input.data()), input.size()));
 }
-#endif // __cplusplus >= 202002L
 
 void resources_inlining_find_refs(
     const UnorderedMap<uint32_t, uint32_t>& past_refs,

libredex/RedexResources.h

@@ -112,11 +112,17 @@ using StringOrReferenceSet =
 // Helper for dealing with differences in character encoding between .arsc and
 // .pb files.
 std::string convert_utf8_to_mutf8(std::string_view input);
-#if __cplusplus >= 202002L
+// This line is needed because this header is exposed to dependents, which may
+// be using C++17.
+// This is not 202002L because GCC 10 (shipped in Debian 11) defines __cplusplus
+// to be so with -std=gnu++20 flag.
+// TODO(T233875592): Change this to 202002L when GCC 11 becomes the minimum
+// supported compiler version.
+#if __cplusplus >= 201709L
 // A convenient wrapper to allow convert_utf8_to_mutf8 to be used with u8"foo"
 // string literals.
 std::string convert_utf8_to_mutf8(std::u8string_view input);
-#endif // __cplusplus >= 202002L
+#endif // __cplusplus >= 201709L
 // Given a map of a id which holds a reference value, and the id that the
 // reference points to, along with all the past found inlinable values, for each
 // id in past_refs, if it is inlinable, adds it to inlinable_resources with the

service/cse/CommonSubexpressionElimination.cpp

@@ -752,8 +752,16 @@ class Analyzer final : public BaseEdgeAwareIRAnalyzer<CseEnvironment> {
       m_pre_state_value_ids.insert(id);
     } else {
       const auto& abs_map = m_shared_state->get_abstract_map();
+#if __GNUC__ >= 11 && __GNUC__ <= 14 && !defined(__clang__)
+#pragma GCC diagnostic push
+// Work around https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116731
+#pragma GCC diagnostic ignored "-Wrange-loop-construct"
+#endif // __GNUC__ >= 11 && __GNUC__ <= 14 && !defined(__clang__)
       for (const auto [box_method, unbox_method] :
            UnorderedIterable(m_shared_state->get_boxing_map())) {
+#if __GNUC__ >= 11 && __GNUC__ <= 14 && !defined(__clang__)
+#pragma GCC diagnostic pop
+#endif // __GNUC__ >= 11 && __GNUC__ <= 14 && !defined(__clang__)
         const DexMethodRef* abs_method = nullptr;
         auto abs_it = abs_map.find(unbox_method);
         if (abs_it != abs_map.end()) {

setup_oss_toolchain.sh

@@ -65,12 +65,13 @@ 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.

test/unit/RedexResourcesTest.cpp

@@ -76,13 +76,8 @@ inline uint32_t to_uint(char c) {
 }
 
 TEST(RedexResources, Mutf8Conversion) {
-#if __cplusplus >= 202002L
-  using utf8_string_view = std::u8string_view;
-#else
-  using utf8_string_view = std::string_view;
-#endif // __cplusplus >= 202002L
   bool be_noisy{false};
-  auto verify = [&](utf8_string_view input,
+  auto verify = [&](std::u8string_view input,
                     const std::vector<uint8_t>& expected_bytes) {
     auto converted = resources::convert_utf8_to_mutf8(input);
     EXPECT_EQ(converted.size(), expected_bytes.size());