weird AC_REQUIRE expansion issue

[Ralf Wildenhues]

I'm currently trying to understand a weird expansion order issue with
Autoconf 2.59 and Automake 1.9.6, and I'd like a hint as to where to
search for the bug.

A project uses subdir-objects, calls AC_PROG_CC before calling
AM_PROG_CC_C_O, yet the code of AC_PROG_CC_C_O (which is AC_REQUIREd by
the Automake macro) gets expanded before the AC_PROG_CC macro.  Thus,
$CC is empty and the test fails.

As a workaround it helps to invoke AC_PROG_CC_C_O before AM_PROG_CC_C_O.
Now, this is surely a bug somewhere, either in Autoconf or in the
Autoconf input of the package.  Since it's huge: where should I start to
look?

The package also uses AM_PROG_AS (and thus needs to save $CC before
the expansion of AC_PROG_CC_C_O), by the way.

Thanks for any help,
Ralf