If you were checking the results of previous tests by examining the
DEFS, you need to switch to checking the values of
the cache variables for those tests.
DEFS no longer exists while
configure is running; it is only created when generating output
files. This difference from version 1 is because properly quoting the
contents of that variable turned out to be too cumbersome and
inefficient to do every time
AC_DEFINE is called. See Cache Variable Names.
For example, here is a configure.ac fragment written for Autoconf version 1:
AC_HAVE_FUNCS(syslog) case "$DEFS" in *-DHAVE_SYSLOG*) ;; *) # syslog is not in the default libraries. See if it's in some other. saved_LIBS="$LIBS" for lib in bsd socket inet; do AC_CHECKING(for syslog in -l$lib) LIBS="-l$lib $saved_LIBS" AC_HAVE_FUNCS(syslog) case "$DEFS" in *-DHAVE_SYSLOG*) break ;; *) ;; esac LIBS="$saved_LIBS" done ;; esac
Here is a way to write it for version 2:
AC_CHECK_FUNCS([syslog]) if test "x$ac_cv_func_syslog" = xno; then # syslog is not in the default libraries. See if it's in some other. for lib in bsd socket inet; do AC_CHECK_LIB([$lib], [syslog], [AC_DEFINE([HAVE_SYSLOG]) LIBS="-l$lib $LIBS"; break]) done fi
If you were working around bugs in
AC_DEFINE_UNQUOTED by adding
backslashes before quotes, you need to remove them. It now works
predictably, and does not treat quotes (except back quotes) specially.
See Setting Output Variables.
All of the Boolean shell variables set by Autoconf macros now use ‘yes’ for the true value. Most of them use ‘no’ for false, though for backward compatibility some use the empty string instead. If you were relying on a shell variable being set to something like 1 or ‘t’ for true, you need to change your tests.