As somebody else has already said, the idea is to use the c++ language and not its runtime or the standard library. In fact, there are a few clang-tidy checks for llvm libc to protect from accidentally using pieces from other libraries (like the system libc and the c++ standard library.) https://clang.llvm.org/extra/clang-tidy/checks/llvmlibc-call... https://clang.llvm.org/extra/clang-tidy/checks/llvmlibc-impl... https://clang.llvm.org/extra/clang-tidy/checks/llvmlibc-rest...