A Module System for C++ is on its way to the C++ standard.
The current state of the Module System, although fairly stable, it has a few bugs for C++ support. The most common reason for the bugs is the semantic merging of C++ entities. Currently, the method for ensuring no regressions is a buildbot for libc++, which builds llvm in modules self-hosted mode. Its main purpose is to find bugs in clang’s implementation and ensure no regression for the ongoing development.
Since the Module Systems is meant to be generic, the project aims to improve the stability and coverage of the Module System by finding as many issues as possible. One approach is to add a buildbot for libstdc++, because this would change the merging model for the modules, and in this way, it will point out different issues which would not be observed by using libc++. The choice for libstdc++ is motivated by its wider use in Unix and, more importantly, the benefits it will bring to supporting modules for third party projects that rely on libstdc++.