At any point in time

at most one *compilation* buffer exists,

with compile and project-compile expecting the user to

rename *compilation* buffers

to run multiple compilations, where

1. if the selected window hosts a buffer in Compilation major mode,

   its compilation process is replaced;

2. else, if any window hosts a buffer named *compilation*,

   its compilation process is replaced;

3. else,

   a new window and buffer named *compilation* is created

   and the compilation process runs there.