A few nits on m4 escapes, but otherwise LGTM - works very well on my system with three versions of Guile installed!
https://codereview.appspot.com/569390043/diff/571710044/aclocal.m4 File aclocal.m4 (right): https://codereview.appspot.com/569390043/diff/571710044/aclocal.m4#newcode693 aclocal.m4:693: if [[ -n "$GUILE_FLAVOR" ]] ; then I first thought this was bash syntax and not portable, but m4 substitution comes into play here and removes one set of [ ]. Could we write this as test -n "$GUILE_FLAVOR" instead? https://codereview.appspot.com/569390043/diff/571710044/aclocal.m4#newcode694 aclocal.m4:694: PKG_CHECK_MODULES(GUILE, $GUILE_FLAVOR, true, true) Please escape all arguments with [ ... ], here and in other locations. Additionally we should probably reset GUILE_FLAVOR in the false case to trigger the error below. https://codereview.appspot.com/569390043/diff/571710044/config.make.in File config.make.in (right): https://codereview.appspot.com/569390043/diff/571710044/config.make.in#newcode28 config.make.in:28: GUILE_LIBS = @GUILE_LIBS@ @GUILE_CFLAGS@ Can be $(GUILE_CFLAGS), already substituted above https://codereview.appspot.com/569390043/diff/571710044/config.make.in#newcode129 config.make.in:129: GUILE_CONFIG = @GUILE_CONFIG@ Please remove these GUILE_CFLAGS (there's another declaration above) and GUILE_CONFIG which should be unused now. https://codereview.appspot.com/569390043/
