In the usual case where Autoconf is creating a @file{config.h} file,
you should include @file{config.h} first, before any other include
file. That way, for example, if @file{config.h} defines
-@samp{restrict} to be the empty string on a pre-C99 host, the
-definition is consistent for all include files.
-
-You should include Gnulib-provided headers before system headers,
-so that Gnulib-provided headers can adjust how a system header
-behaves.
+@samp{restrict} to be the empty string on a pre-C99 host, or a macro
+like @samp{_FILE_OFFSET_BITS} that affects the layout of data
+structures, the definition is consistent for all include files.
+Also, on some platforms macros like @samp{_FILE_OFFSET_BITS} and
+@samp{_GNU_SOURCE} may be ineffective, or may have only a limited
+effect, if defined after the first system header file is included.
A final word of warning: Gnulib currently assumes it will be
responsible for @emph{all} functions that end up in the Autoconf