Re: Can't call AC_PROG_CXX conditionally

[Akim Demaille]

 Andreas> When AC_PROG_CXX is used conditionally then the generated
 Andreas> configure script complains that conditional "am__fastdepCXX"
 Andreas> was never defined when AC_PROG_CXX is not actually called.
 Andreas> In a real-world example this would depend on some --enable
 Andreas> or --with option.

Do not do this.  I know it's a pain, but this is really something not
to do.

Actually, in the real world, I would suggest AC_CONFIG_SUBDIR'ing the
part in C++.  Or maybe...

m4_pushdef([AC_MSG_ERROR])
AC_PROG_CXX
m4_popdef([AC_PROG_CXX])

Something should be done, agreed.