Changeset 4829 at http://allmydata.org/trac/darcs-2/changeset/4829/ added a
check for termio.h.  Sometime since then (I haven't determined when), the stanza
was removed, (I checked current) which breaks the build on Solaris machines.  I
am using the 2.1.0 release tarball.

While checking my build configuration, I also noticed that the following are
also undefined in autoconf.mk -- @USE_GNULIBSHA1@ @HAVE_LIBCURL@ @HAVE_LIBWWW@
@WXFLAGS@, even though libcurl 7.19.0 was found.

It looks like David erroneously removed the check from configure.ac

  $ darcs cha -v -p 'termio\.h'
  Fri Apr 18 03:24:27 EST 2008  David Roundy <droundy@darcs.net>
    * remove unneeded check for termio.h.
      hunk ./configure.ac 496
      -  AC_CHECK_HEADERS([termio.h], [HAVE_TERMIO_H=True]) dnl see External.hs
      hunk ./configure.ac 501
      -AC_SUBST(HAVE_TERMIO_H)

Note that HAVE_TERMIO_H is still used in autoconf.mk and GNUmakefile,
so the above patch was a bit hokey.

But Darcs won't let me just roll back that change, because it has
dependencies.

  $ darcs rollback -p 'termio\.h'
  No patches selected!

If you add these lines back into configure.ac, does Darcs work again
for you on Solaris?

dwc: Hi, I suspect that our switching to a new build system (cabal) has fixed
something like this along the way.  It'd be great if you could try out Darcs 2.3
and let us know if you run into any more trouble.  Thanks!