libc++1 4.0.1-2 (s390x binary) in ubuntu bionic

 libc++ is a new implementation of the C++ standard library, targeting C++11.
 .
 Features and Goals
 .
   * Correctness as defined by the C++11 standard.
   * Fast execution.
   * Minimal memory use.
   * Fast compile times.
   * ABI compatibility with gcc's libstdc++ for some low-level features such
     as exception objects, rtti and memory allocation.
   * Extensive unit tests.