M4. Each package team must do a “best effort” at portability to common platforms, including standard Linux distributions, and common compiler toolchains such as GNU, Clang,4 and vendor compilers. Further portability requirements for xSDK subsets may be conditionally applied based on sponsor requirements.5 Support for Apple Mac OS and Microsoft Windows Visual Studio is recommended.
4 This does not mean that xSDK packages and all their dependencies cannot have a dependency of Fortran, merely that the C and C++ portions of the packages and their dependencies should be compilable with the Clang compilers.
5 For example, xSDK packages that receive funding from the mathematical libraries component of the U.S. Department of Energy (DOE) Exascale Computing Project (ECP) must support portability to target machines at the computing facilities ALCF, NERSC, and OLCF.