I don't have a test case for this but noticed this warning when including system headers with -I rather than -isystem.
In file included from <built-in>:1: In file included from /nix/store/jq6bpm0xmhnbffhs5rkxq4n88g5xi2zg-clang-wrapper-11.0.1/resource-root/include/__clang_cuda_runtime_wrapper.h:157: /nix/store/jq6bpm0xmhnbffhs5rkxq4n88g5xi2zg-clang-wrapper-11.0.1/resource-root/include/__clang_cuda_math.h:39:25: warning: extra tokens at end of #ifdef directive [-Wextra-tokens] #ifdef __OPENMP_NVPTX__ && defined(__cplusplus) && __cplusplus < 201402L ^