4.3. AC_ARG_ENABLE

AC_ARG_ENABLE allows you to define another command line option.
It accepts three arguments:
1. The flag base: the flag would be --enable-[option base]
2. The help for this option
3. The code to execute when the configure script is invoked with this option. In it the command line variable enableval would be set to the argument
Examples:

AC_ARG_ENABLE(debug-rwlock,
 [  --enable-debug-rwlock  Enable an RWLock that prints debug notices \
  on the screen. This is a debugging feature which should not be \
  usually enabled],
 [ debug_rwlock=yes
 ])

AC_ARG_ENABLE(states-type,
 [  --enable-states-type[=state type] Specify the states type:
                      compact [default]: Compact States
                      debug: Debug States (very slow)
                      indirect: Indirect Stack States],
 [ if   test "x$enableval" = "xcompact" ; then
      states_type=compact
   elif test "x$enableval" = "xdebug" ; then
      states_type=debug
   elif test "x$enableval" = "xindirect" ; then
      states_type=indirect
   else
      echo
      echo "Error!"
      echo "Unknown states' type"
      exit -1
   fi
 ])