C++17 defines the __cpp_aligned_new feature test macro and and according to https://en.cppreference.com/w/cpp/feature_test this is included in the cxx17_core group of feature test macros. In the 'new' header file this feature test is used to gate the definition of std::align_t. However, it appears that clang15 with -std=c++20 somehow doesn't enable this feature flag and therefore code that we define that uses a std::align_t fails to compile.
Looking at the clang source (https://clang.llvm.org/doxygen/InitPreprocessor_8cpp_source.html) the __cpp_aligned_new feature macro is enabled separately to the block of cxx17 macros and is under the AlignedAllocation langopt. I'm not sure why this is so but we'll justset the language option in the driver and that appears to work fine.
Summary
C++17 defines the
__cpp_aligned_newfeature test macro and and according to https://en.cppreference.com/w/cpp/feature_test this is included in thecxx17_coregroup of feature test macros. In the 'new' header file this feature test is used to gate the definition ofstd::align_t. However, it appears that clang15 with-std=c++20somehow doesn't enable this feature flag and therefore code that we define that uses astd::align_tfails to compile.Looking at the clang source (https://clang.llvm.org/doxygen/InitPreprocessor_8cpp_source.html) the
__cpp_aligned_newfeature macro is enabled separately to the block of cxx17 macros and is under theAlignedAllocationlangopt. I'm not sure why this is so but we'll justset the language option in the driver and that appears to work fine.Test plan
Internally tested.