[RFC, fortran] Output contained namespaces in module (PR fortran/16861)

[David Edelsohn <dje at watson dot ibm dot com>]

	write_module() saves the compiler's symbol information, including
symtrees.  The function traverses the current namespace, but a namespace
may contain additional namespaces, which the current algorithm omits.
This leads to the failure described in the PR where a module USE results
in an ICE because a symbol's symtree is NULL.  The symtree was not loaded
because it was not written.

	The following patch is a start at a fix.  The patch modifies
write_module() to output contained namespaces.  This presumably needs to
be expanded to walk the entire tree of namespaces.

	This patch also modifies write_symtree() to skip MODULE symbols.
Without that change, find_pointer() returns NULL provoking a "Symbol not
written" error.  Also, gfortran with the proposed patch will emit some
symbols multiple times -- this is not wrong, but is inefficient.

	My main questions are: What symbols from contained namespaces
should be omitted and how can I recognize those symbols?

Thanks, David


	PR fortran/16861
	* module.c (write_symtree): Skip MODULE symbols.
	(write_module): Write symtree for contained namespaces.

Index: module.c
===================================================================
RCS file: /cvs/gcc/gcc/gcc/fortran/module.c,v
retrieving revision 1.34
diff -c -p -r1.34 module.c
*** module.c	25 Jun 2005 00:40:35 -0000	1.34
--- module.c	15 Jul 2005 15:11:18 -0000
*************** write_symtree (gfc_symtree * st)
*** 3393,3399 ****
    sym = st->n.sym;
    if (!gfc_check_access (sym->attr.access, sym->ns->default_access)
        || (sym->attr.flavor == FL_PROCEDURE && sym->attr.generic
! 	  && !sym->attr.subroutine && !sym->attr.function))
      return;
  
    if (check_unique_name (st->name))
--- 3393,3400 ----
    sym = st->n.sym;
    if (!gfc_check_access (sym->attr.access, sym->ns->default_access)
        || (sym->attr.flavor == FL_PROCEDURE && sym->attr.generic
! 	  && !sym->attr.subroutine && !sym->attr.function)
!       || (sym->attr.flavor == FL_MODULE))
      return;
  
    if (check_unique_name (st->name))
*************** static void
*** 3413,3418 ****
--- 3414,3420 ----
  write_module (void)
  {
    gfc_intrinsic_op i;
+   gfc_namespace *ns;
  
    /* Write the operator interfaces.  */
    mio_lparen ();
*************** write_module (void)
*** 3468,3473 ****
--- 3470,3477 ----
  
    mio_lparen ();
    gfc_traverse_symtree (gfc_current_ns->sym_root, write_symtree);
+   for (ns = gfc_current_ns->contained; ns; ns = ns->sibling)
+     gfc_traverse_symtree (ns->sym_root, write_symtree);
    mio_rparen ();
  }