Paul Eggert wrote:
> PS. I vaguely recall a long discussion many years ago when we added this
> AC_REQUIRE-ish stuff to Autoconf. Although we did fix some major
> glitches, we replacing them with other glitches that live on to this
> day. For example, there's now this note in the Autoconf manual:
>
> Many Autoconf macros use a compiler, and thus call
> `AC_REQUIRE([AC_PROG_CC])' to ensure that the compiler has been
> determined before the body of the outermost `AC_DEFUN' macro.
> Although `AC_PROG_CC' is safe to directly expand multiple times, it
> performs certain checks (such as the proper value of `EXEEXT') only
> on the first invocation.
and likewise for AC_EGREP_CPP, whose definition starts like this:
AC_DEFUN([AC_EGREP_CPP],
[AC_LANG_PREPROC_REQUIRE()dnl
AC_REQUIRE([AC_PROG_EGREP])dnl
...
where AC_LANG_PREPROC_REQUIRE() in this case requires AC_LANG_COMPILER(C).
So, you could also run into trouble if the first AC_EGREP_CPP invocation
in a configure.ac is within
case "$host_os" in
alpha*)
AC_EGREP_CPP(...)
;;
esac
Bruno
