[Bug middle-end/27945] [4.0/4.1/4.2/4.3 Regression] Packed struct of variable length has wrong size

["jason at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #8 from jason at gcc dot gnu dot org  2006-11-14 01:10 -------
Ah, I see the problem.  The code I removed from the C and C++ front ends was
redundant with code in layout_decl, except that the code in layout_decl
deliberately ignores DECL_PACKED for fields of variable size.

      /* If the field is of variable size, we can't misalign it since we        
         have no way to make a temporary to align the result.  But this         
         isn't an issue if the decl is not addressable.  Likewise if it         
         is of unknown size.                                                    

         Note that do_type_align may set DECL_USER_ALIGN, so we need to         
         check old_user_align instead.  */
=>    if (packed_p
          && !old_user_align
          && (DECL_NONADDRESSABLE_P (decl)
              || DECL_SIZE_UNIT (decl) == 0
              || TREE_CODE (DECL_SIZE_UNIT (decl)) == INTEGER_CST))
        DECL_ALIGN (decl) = MIN (DECL_ALIGN (decl), BITS_PER_UNIT);

This dates back to a change of Kenner's from 2001:

Sat Dec 29 15:48:54 2001  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>

        * stor-layout.c (layout_decl): Don't misalign field of variable size
        for packed record.

Richard, do you have any input?  Do you think there a way to make that test
more specific to the case were fixing?


-- 

jason at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |kenner at vlsi1 dot ultra
                   |                            |dot nyu dot edu
         AssignedTo|unassigned at gcc dot gnu   |jason at gcc dot gnu dot org
                   |dot org                     |
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2006-06-09 07:45:54         |2006-11-14 01:10:19
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27945