Re: Dependence on object files listed in link script

[Stepan Kasal]

Hello,

On Wed, Oct 04, 2006 at 11:59:40AM +0800, Tzu-Chien Chiu wrote:
> Makefile.am
> bin_PROGRAMS = bar
> bar_LDADD = @top_builddir@/xyz.la
> bar_DEPENDENCIES = $(bar_LDADD) @many_objs@

a few nits first:  all AC_SUBSTed variables are available as make
variables, so you can use $(top_builddir) and $(many_objs).
Actually, this is the prefferred way.

Consequently, you can use
        many_objs='$(top_builddir)/foo.lo ...'
in your configure.ac.

Another nit: if the above snippet comes from top level Makefile, then
there is no reason to use top_builddir; top builddir is the current
directory.  This simplifies the situation:

configure.ac:
many_objs='foo.lo ...'
AC_SUBST(many_objs)

Makefile.am:
bin_PROGRAMS = bar
bar_LDADD = xyz.la
bar_DEPENDENCIES = $(bar_LDADD) $(many_objs)

linkscript.ld:
SECTIONS {
 .a: { foo.o }
 ..
}

> When the number of object files grows, it's difficult to maintain
> these files. Better approach anyone, please?

I can see only one remaining problem: both linkscript.ld and
configure.ac contain the same long list of objects.
Then you can select one file, which will have the list, and the other
ones will be generated.

First solution:
linkscript.ld would be the primary source, and configure.ac would do
this:
many_objs=`sed -n '/^SECTIONS/,/^}/{
  s|.*{ *\(.*\)\.o *}.*|$(top_builddir)/\1.lo|p
}' $srcdir/linkscript.ld |tr '\n' ' '`

Another solution:
linkscript.ld might be generated by a rule in Makefile.
Actyally, the variable many_objs could be defined directly in
Makefile.am, too.  Something like this:

many_objs = foo.lo bar.lo ..

linkscript.ld: Makefile
        ( \
        echo "SECTIONS {"; \
        for obj in $(many_objs:.lo=.o); do \
          echo "  .a { $$obj }"; \
        echo "}"; \
        ) >$@

Or you can write an awk or ruby script to generate linkscript.ld from
a list of object files passed as parameters. 

Actually, I'm afraid that you real situation might be a bit more
complicated than the simplified example which you posted, but I hope
that you find my suggestions inspirative anyway.
If a problem remains, feel free to ask again.

Have a nice day,
        Stepan Kasal