Re: _SOURCES to _OBJECTS transform

[Tom Tromey <tromey@cygnus.com>]

>>>>> "Mark" == Mark Frost <mfrost@horizsys.com> writes:

Mark> Hello.  I'm new to this list and pretty new to
Mark> automake/autoconf/libtool.  I'm trying to resolve issues with
Mark> building the gxsnmp package on Solaris (SPARC) 2.6.

Mark> From the resulting Makefile, I can see that a
Mark> libgxsnmp_la_OBJECTS gets constructed that seems to elimate the
Mark> header files and converts the *.c files into *.lo files.

Mark> My problem is that I cannot seem to find a way to conditionally
Mark> insert the getopt?.c *and* the getopt*.lo files/references into
Mark> the Makefile.am -> Makefile.in process.

There are two ways to do this.

The "old" way (meaning still workable but somewhat confusing) is to
put something like this in Makefile.am:

	libgxsnmp_la_LIBADD = @magic@
	libgxsnmp_la_DEPENDENCIES = @magic@
	EXTRA_libgxsnmp_la_SOURCES = getopt.c getopt1.c

and then in configure.in:

	magic=
	AC_SUBST(magic)
	if test whatever; then
	    magic="getopt.lo getopt1.lo"
	fi


The "new" (meaning somewhat less confusing) way to do this is to use a
conditional.  In configure.in:

	AM_CONDITIONAL(WANT_GETOPT, test whatever)

In Makefile.am:

	if WANT_GETOPT
	g_sources = getopt.c getopt1.c
	else
	g_sources =
	endif

	libgxsnmp_la_SOURCES = $(g_sources) ...

Mark>     libgxsnmp_la_SOURCES =
Mark> 	    g_access.h	\
Mark> 	    ...		\
Mark> 	    @GETOPT_SRC@

This can't work because the source list must be known statically --
there is no (good) way to do the `.c->.lo' transformation at
make-time.

Automake ought to give an error if you try to do this.  Unfortunately
it (currently) doesn't.

Mark> I've tried fiddling with EXTRA_libgxsnmp_la_SOURCES, also no
Mark> luck.  If I add the getopt*lo references using the "_LIBADD"
Mark> functionality, I find that it wants to link the getopt*lo
Mark> objects, but it never builds them.

You are close!  You just need to set the _DEPENDENCIES variable.  (If
you want the "old" way.  I personally much prefer using conditionals.)

Tom