C++ modules-ts[1] proposes a module system, with defined interfaces, implementations and importing. I shall outline the new semantics, their impact on the ABI and build systems, and discuss the, in-progress, implementation in the GNU C++ Compiler.
[1] JTC1/SC22/WG21/n4681, 'Working Draft, Extensions to C++ for Modules', 2017-07-14, Gabriel Dos Reis