"Autoconf is an extensible package of m4 macros that produce shell scripts to automatically configure software source code packages," according to its official home page [L1 ]. But it really is ... for the purpose of ...
autoconf acts on configure.in to generate configure.
This [L2 ] "Compile-Howto" usefully introduces autoconf.
drh describes "Using Autoconf With Mktclapp" [L3 ].
"Stop the autoconf insanity! Why we need a new build system." [L4 ]
[Refer to TIP 34?]