CppCon 2021

C++ Modules are a tooling opportunity. For example, a common implementation strategy for compilers is to save on disk the abstract semantics graph (ASG) obtained from elaborating a module interface (exported), to be reused later when that module is consumed (imported). That ASG, an intermediate representation, saves the compiler from repeated work in common scenarios, therefore helps achieve substantial reduction in compilation time. In essence, ISO C++ compilers are practically compelled to acknowledge representations of C++ program fragments other than character streams stored in source files. It is all too tempting to view these ASGs as mere build artifact curiosities. If N compilers, on a given platform, decide to use N different on-disk ASG representation formats then we face a severe problem of developer tools fragmentation. I present, in this talk, how the C++ community can avoid that problem: the desiggn and implementation of formal, compiler-neutral in-memory and persistent representations of C++ programs. These alternative representations allow tools to process C++ programs without needing to master or to replicate the dark art of C++ compiler construction. These representations are available either as open specification, or as C++ libraries. The application opportunities range from automated generation of bindings ("foreign function/data interface") to Just-In-Time compilation of interpreted C++ scripts, and beyond.