15.6.2 New Macros

Because Autoconf has been dormant for years, Automake provided Autoconf-like macros for a while. Autoconf 2.50 now provides better versions of these macros, integrated in the AC_ namespace, instead of AM_. But in order to ease the upgrading via autoupdate, bindings to such AM_ macros are provided.

Unfortunately Automake did not quote the names of these macros! Therefore, when m4 finds something like `AC_DEFUN(AM_TYPE_PTRDIFF_T, ...)' in `aclocal.m4', AM_TYPE_PTRDIFF_T is expanded, replaced with its Autoconf definition.

Fortunately Autoconf catches pre-AC_INIT expansions, and will complain, in its own words:

$ cat configure.in AC_INIT AM_TYPE_PTRDIFF_T $ aclocal-1.4 $ autoconf ./aclocal.m4:17: error: m4_defn: undefined macro: _m4_divert_diversion actypes.m4:289: AM_TYPE_PTRDIFF_T is expanded from... ./aclocal.m4:17: the top level $

Future versions of Automake will simply no longer define most of these macros, and will properly quote the names of the remaining macros. But you don't have to wait for it to happen to do the right thing right now: do not depend upon macros from Automake as it is simply not its job to provide macros (but the one it requires itself):

$ cat configure.in AC_INIT AM_TYPE_PTRDIFF_T $ rm aclocal.m4 $ autoupdate autoupdate: `configure.in' is updated $ cat configure.in AC_INIT AC_CHECK_TYPES([ptrdiff_t]) $ aclocal-1.4 $ autoconf $