--- a/configure.ac	Wed Oct 18 19:10:29 2017 +0200
+++ b/configure.ac	Fri Oct 20 13:50:13 2017 +0200
@@ -1,14 +1,37 @@
 # the package version must match the macros in ucx.h
 # if you change the package version, don't forget to adjust the library version
 AC_INIT([ucx], [0.14], [olaf.wintermann@gmail.com])
+
+# don't place everything in the project root
 AC_CONFIG_AUX_DIR([build-aux])
 AC_CONFIG_MACRO_DIR([m4])
+
+# we use our own directory structure
 AM_INIT_AUTOMAKE([foreign -Wall -Werror])
+
+# if there is an archiver, use it
 m4_ifdef([AM_PROG_AR], [AM_PROG_AR])
+
+# we are compiling a library
 LT_INIT
+
+# we are dealing with C source code
 AC_PROG_CC
+
+# we want to support automake < 1.14, so we need this deprecated macro
+# it tests, whether the compiler allows -c and -o simultaneously
+# in modern versions of autoconf, this is done by AC_PROG_CC
+AM_PROG_CC_C_O
+
+# we require the current C standard
 AC_PROG_CC_STDC
+
+# where to place config macros
 AC_CONFIG_HEADERS([config.h])
+
+# our Makefiles
 AC_CONFIG_FILES([Makefile src/Makefile test/Makefile])
+
+# GO
 AC_OUTPUT