MPIL_Comm_id(3) on Linux
The text 594dbf675827, as Debian 13 (Trixie), Debian 12 (Bookworm), Debian 11 (Bullseye), Debian 10 (Buster), Debian 9 (Stretch), Debian 8 (Jessie), Debian 7 (Wheezy) shipped it. The page shows this text now.
LAM/MPI-specific function to return the context ID of the communicator