|  |  C.4 autoconf 
autoconfexpands them4macros in
`configure.in', perhaps using macro definitions from
`aclocal.m4', to generate theconfigurescript. 
 |  | user input files   optional input   processes          output files
================   ==============   =========          ============
                   aclocal.m4 - - - - - -.
                                         V
                                     .--------,
configure.in ----------------------->|autoconf|------> configure
                                     `--------'
 | 
 
 |