Conditional modules and libraries.

[Bill Moseley]

Still trying to convert an existing project to automake and libtool.  I've
tried to read all the docs (a few times), but it's still not clear for me.

I have a single Makefile.am that builds a binary, a installed library
and a convenience library.  (That's the result of most of the code being
in a "src" directory.)  I suspect the mutliple libs in one directory is
one of my problems.

I want to add conditional support (e.g. --with-libxml2) to one of the
libraries (a convenience library).  I have parser.c and parser.h I also
link in with using liblxm2.

If I was just building a single product I would think it would be correct
to adjust LIBS and CPPFLAGS in my configure script and call
AC_LIBOBJS(parser) which would set LIBOBJS (or in my case LTLIBOBJS).  But
in this case I don't want parser.o and -lxml2 linked with other libraries.

My existing configure.in script checks for libxml2 and then sets:

    AC_DEFINE(HAVE_LIBXML2,[],[libxml support])
    LIBXML2_OBJS="parser.lo"
    AC_SUBST(LIBXML2_OBJS)

    AC_SUBST(LIBXML2_LIB)
    AC_SUBST(LIBXML2_CFLAGS)

The last two are set from xml2-config --libs and --cflags commands.

I use parser.lo because I'm building with libtool, but I'm not sure if
that's the correct method.

So, what I'm trying is:

AM_CPPFLAGS = @LIBXML2_CFLAGS@ @Z_CFLAGS@

[other library and binary built in this Makefile.am snipped]

noinst_LTLIBRARIES = libswishindex.la
libswishindex_la_LIBADD = @LIBXML2_LIB@ @LIBXML2_OBJS@  sw_expat/libswexpat.la
libswishindex_la_DEPENDENCIES = @LIBXML2_OBJS@
##libswishindex_la_LDADD = @LIBXML2_OBJS@
EXTRA_libswishindex_la_SOURCES = parser.c parser.h

libswishindex_la_SOURCES = \
        fs.c fs.h \
        http.c http.h \
        ...

Automake is telling me to use LIBADD not LDADD although I was trying to
follow the example on page 43 of the Autoconf book -- I still don't get
the difference between LDADD and LIBADD.

So, basically:

- I want to conditionally add -lxml2 and the CPPFLAGS and the parser.o
module in only that one convenience library.  I guess it doesn't hurt
that AM_CPPFLAGS adds the flags to the other library build, but it would
seem best to add them just when building parser.o.

- I do not understand what the DEPENDENCIES entry does, if anything.  Is
that needed?

By the way, how can I force the complete rebuiding of just one
(convenience) library without rebuilding everything?

Thanks,





-- 
Bill Moseley address@hidden