Deal with the inferior unloading shared objects.

* solib.c (current_sos): New function, replacing find_solib.
(find_solib): Deleted.
(free_so): New function.
(clear_solib): Call free_so, instead of writing it out.
(solib_add): Rewritten: compare the inferior's current list of
shared objects with GDB's list, and do the required loads and
unloads.
(info_sharedlibrary_command, solib_address): Don't use find_solib
to walk the list of shared libraries: call solib_add, and then
walk the list at so_list_head normally.
* objfiles.c (free_objfile): Don't call CLEAR_SOLIB, and don't
detach the core target.  These tasks are taken care of elsewhere.
* target.c (remove_target_sections): New function.
* target.h (remove_target_sections): New declaration.

* solib.c (symbol_add_stub): Check whether we've already created
an objfile for this shared object first, before doing all that
work to compute section addresses, etc.

* objfiles.c (unlink_objfile): Report an internal error if objfile
doesn't occur in the object_files list.

* solib.c (special_symbol_handling): Delete argument; it's not
used.

* solib.c (SOLIB_EXTRACT_ADDRESS):  New macro to extract addresses
from solib structures. Use it throughout solib.c, get rid of all
CORE_ADDR casts.
(struct so_list):  Change type of lmaddr to CORE_ADDR.
(first_link_map_member):  Change return value type to CORE_ADDR,
update callers.
(solib_add_common_symbols):  Change parameter type to CORE_ADDR,
update callers.
(open_symbol_file_object, find_solib):  Change type of lm variable
to CORE_ADDR.

gdb/target.c

@@ -1325,6 +1325,39 @@ target_resize_to_sections (struct target_ops *target, int num_added)
 
 }
 
+/* Remove all target sections taken from ABFD.
+
+   Scan the current target stack for targets whose section tables
+   refer to sections from BFD, and remove those sections.  We use this
+   when we notice that the inferior has unloaded a shared object, for
+   example.  */
+void
+remove_target_sections (bfd *abfd)
+{
+  struct target_ops **t;
+
+  for (t = target_structs; t < target_structs + target_struct_size; t++)
+    {
+      struct section_table *src, *dest;
+
+      dest = (*t)->to_sections;
+      for (src = (*t)->to_sections; src < (*t)->to_sections_end; src++)
+	if (src->bfd != abfd)
+	  {
+	    /* Keep this section.  */
+	    if (dest < src) *dest = *src;
+	    dest++;
+	  }
+
+      /* If we've dropped any sections, resize the section table.  */
+      if (dest < src)
+	target_resize_to_sections (*t, dest - src);
+    }
+}
+
+
+
+
 /* Find a single runnable target in the stack and return it.  If for
    some reason there is more than one, return NULL.  */