RFA: improve error reporting for `overlay auto' operations

[Jim Blandy <jimb at zwingli dot cygnus dot com>]

Michael, symfile.c is supposedly my area of maintainership, but this
is overlay stuff; could you check it over for sanity?

2001-10-11  Jim Blandy  <jimb@redhat.com>

	* symfile.c (simple_read_overlay_table): Make sure we can find
	both `_novlys' and `_ovly_table' before we try anything else;
	print a helpful error message.
	(simple_overlay_update): No need to print error message here.

Index: gdb/symfile.c
===================================================================
RCS file: /cvs/cvsfiles/devo/gdb/symfile.c,v
retrieving revision 1.239
diff -c -r1.239 symfile.c
*** gdb/symfile.c	2001/09/07 18:36:51	1.239
--- gdb/symfile.c	2001/10/11 22:17:08
***************
*** 3025,3054 ****
  static int
  simple_read_overlay_table (void)
  {
!   struct minimal_symbol *msym;
  
    simple_free_overlay_table ();
!   msym = lookup_minimal_symbol ("_novlys", 0, 0);
!   if (msym != NULL)
!     cache_novlys = read_memory_integer (SYMBOL_VALUE_ADDRESS (msym), 4);
!   else
!     return 0;			/* failure */
!   cache_ovly_table = (void *) xmalloc (cache_novlys * sizeof (*cache_ovly_table));
!   if (cache_ovly_table != NULL)
      {
!       msym = lookup_minimal_symbol ("_ovly_table", 0, 0);
!       if (msym != NULL)
! 	{
! 	  cache_ovly_table_base = SYMBOL_VALUE_ADDRESS (msym);
! 	  read_target_long_array (cache_ovly_table_base,
! 				  (int *) cache_ovly_table,
! 				  cache_novlys * 4);
! 	}
!       else
! 	return 0;		/* failure */
      }
!   else
!     return 0;			/* failure */
    return 1;			/* SUCCESS */
  }
  
--- 3025,3059 ----
  static int
  simple_read_overlay_table (void)
  {
!   struct minimal_symbol *novlys_msym, *ovly_table_msym;
  
    simple_free_overlay_table ();
!   novlys_msym = lookup_minimal_symbol ("_novlys", 0, 0);
!   if (! novlys_msym)
      {
!       error ("Error reading inferior's overlay table: "
!              "couldn't find `_novlys' variable\n"
!              "in inferior.  Use `overlay manual' mode.");
!       return 0;
      }
! 
!   ovly_table_msym = lookup_minimal_symbol ("_ovly_table", 0, 0);
!   if (! ovly_table_msym)
!     {
!       error ("Error reading inferior's overlay table: couldn't find "
!              "`_ovly_table' array\n"
!              "in inferior.  Use `overlay manual' mode.");
!       return 0;
!     }
! 
!   cache_novlys = read_memory_integer (SYMBOL_VALUE_ADDRESS (novlys_msym), 4);
!   cache_ovly_table
!     = (void *) xmalloc (cache_novlys * sizeof (*cache_ovly_table));
!   cache_ovly_table_base = SYMBOL_VALUE_ADDRESS (ovly_table_msym);
!   read_target_long_array (cache_ovly_table_base,
!                           (int *) cache_ovly_table,
!                           cache_novlys * 4);
! 
    return 1;			/* SUCCESS */
  }
  
***************
*** 3149,3159 ****
       Or else we want all the sections, in which case it's actually
       more efficient to read the whole table in one block anyway.  */
  
!   if (simple_read_overlay_table () == 0)	/* read failed?  No table? */
!     {
!       warning ("Failed to read the target overlay mapping table.");
!       return;
!     }
    /* Now may as well update all sections, even if only one was requested. */
    ALL_OBJSECTIONS (objfile, osect)
      if (section_is_overlay (osect->the_bfd_section))
--- 3154,3162 ----
       Or else we want all the sections, in which case it's actually
       more efficient to read the whole table in one block anyway.  */
  
!   if (! simple_read_overlay_table ())
!     return;
! 
    /* Now may as well update all sections, even if only one was requested. */
    ALL_OBJSECTIONS (objfile, osect)
      if (section_is_overlay (osect->the_bfd_section))