Currently I'm only pulling data from package managers like rubygems and npm, I couldn't find a C++ one yet, although https://www.biicode.com/ looks handy for that, I'll investigate.
C and C++ is usually packaged with the OS's package manager, like dpkg, rpm, pacman, etc.
The closest thing to rubygems might be Portage (1) or AUR (2). You might be able to search each of those for "c++". Or maybe peek into the constituent files for '.c' or '.cpp', '.cxx', etc.