roots.add(toSpec(sourceTree))
        }
    }

    private
    fun fromSpec(spec: FileTreeSpec): FileTreeInternal = when (spec) {
        is AdaptedFileTreeSpec -> fileCollectionFactory.treeOf(spec.tree)
        is FilteredFileTreeSpec -> spec.tree.matching(spec.patterns)
        is FilteredMinimalFileTreeSpec -> fromSpec(spec.tree).matching(spec.patterns)
        is WrappedFileCollectionTreeSpec -> spec.collection.asFileTree

		// objects, try to read them from the libgcc file.
		any := false
		undefs, froms := ctxt.loader.UndefinedRelocTargets(1)
		if len(undefs) > 0 {
			any = true
			if ctxt.Debugvlog > 1 {
				ctxt.Logf("loadlib: first unresolved is %s [%d] from %s [%d]\n",
					ctxt.loader.SymName(undefs[0]), undefs[0],
					ctxt.loader.SymName(froms[0]), froms[0])
			}
		}
		if any {
			if *flagLibGCC == "" {