[Bug middle-end/28160] Bogus "size of array 'foo' is too large" error with -mms-bitfields

["kkojima at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>]

------- Comment #4 from kkojima at gcc dot gnu dot org  2006-06-26 22:42 -------
Thanks for your comment. Perhaps one solution would be to handle
such bit fields with excessive sizes as the case of "no remaining
bits in alignment".  I'm testing the appended patch which changes
lines you've pointed out.

--- ORIG/trunk/gcc/stor-layout.c        2006-06-13 09:06:36.000000000 +0900
+++ LOCAL/trunk/gcc/stor-layout.c       2006-06-26 16:43:12.000000000 +0900
@@ -1047,17 +1047,20 @@ place_field (record_layout_info rli, tre

              if (rli->remaining_in_alignment < bitsize)
                {
+                 HOST_WIDE_INT typesize = tree_low_cst (TYPE_SIZE (type), 1);
+
                  /* out of bits; bump up to next 'word'.  */
-                 rli->offset = DECL_FIELD_OFFSET (rli->prev_field);
                  rli->bitpos
-                   = size_binop (PLUS_EXPR, TYPE_SIZE (type),
-                                 DECL_FIELD_BIT_OFFSET (rli->prev_field));
+                   = size_binop (PLUS_EXPR, rli->bitpos,
+                                 bitsize_int (rli->remaining_in_alignment));
                  rli->prev_field = field;
-                 rli->remaining_in_alignment
-                   = tree_low_cst (TYPE_SIZE (type), 1);
+                 if (typesize < bitsize)
+                   rli->remaining_in_alignment = 0;
+                 else
+                   rli->remaining_in_alignment = typesize - bitsize;
                }
-
-             rli->remaining_in_alignment -= bitsize;
+             else
+               rli->remaining_in_alignment -= bitsize;
            }
          else
            {
@@ -1119,9 +1121,16 @@ place_field (record_layout_info rli, tre
          if (DECL_SIZE (field) != NULL
              && host_integerp (TYPE_SIZE (TREE_TYPE (field)), 0)
              && host_integerp (DECL_SIZE (field), 0))
-           rli->remaining_in_alignment
-             = tree_low_cst (TYPE_SIZE (TREE_TYPE(field)), 1)
-               - tree_low_cst (DECL_SIZE (field), 1);
+           {
+             HOST_WIDE_INT bitsize = tree_low_cst (DECL_SIZE (field), 1);
+             HOST_WIDE_INT typesize
+               = tree_low_cst (TYPE_SIZE (TREE_TYPE (field)), 1);
+
+             if (typesize < bitsize)
+               rli->remaining_in_alignment = 0;
+             else
+               rli->remaining_in_alignment = typesize - bitsize;
+           }

          /* Now align (conventionally) for the new type.  */
          type_align = TYPE_ALIGN (TREE_TYPE (field));


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28160