[libc++] Require a C++20 capable compiler.

This enforces libcxx and its benchmarks are compiled by a C++20 capable
compiler. Based on review comments in D103413.

Differential Revision: https://reviews.llvm.org/D110338

diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index 924a9f1..6ab44e5 100644 (file)
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -537,7 +537,7 @@ function(cxx_add_basic_build_flags target)
   # in the dylib. C++20 is needed to use char8_t.
   set_target_properties(${target} PROPERTIES
     CXX_STANDARD 20
-    CXX_STANDARD_REQUIRED NO
+    CXX_STANDARD_REQUIRED YES
     CXX_EXTENSIONS NO)
 
   # When building the dylib, don't warn for unavailable aligned allocation

diff --git a/libcxx/benchmarks/CMakeLists.txt b/libcxx/benchmarks/CMakeLists.txt
index 8d83ecd..cad8808 100644 (file)
--- a/libcxx/benchmarks/CMakeLists.txt
+++ b/libcxx/benchmarks/CMakeLists.txt
@@ -81,7 +81,7 @@ set(BENCHMARK_LIBCXX_INSTALL ${CMAKE_CURRENT_BINARY_DIR}/benchmark-libcxx)
 set(BENCHMARK_NATIVE_INSTALL ${CMAKE_CURRENT_BINARY_DIR}/benchmark-native)
 
 add_library(               cxx-benchmarks-flags INTERFACE)
-target_compile_features(   cxx-benchmarks-flags INTERFACE cxx_std_17)
+target_compile_features(   cxx-benchmarks-flags INTERFACE cxx_std_20)
 target_compile_options(    cxx-benchmarks-flags INTERFACE -O2 -fsized-deallocation)
 target_include_directories(cxx-benchmarks-flags INTERFACE "${BENCHMARK_LIBCXX_INSTALL}/include"
                                                 INTERFACE "${LIBCXX_SOURCE_DIR}/test/support")