Re: [patch] Prevent memory explosion for big discriminated types

[Eric Botcazou]

> > The patch plugs the hole by invoking it for DECL_FIELD_OFFSET as well
> > (and the effect is spectacular for pathological cases).  Tested on
> > x86_64-suse-linux, although this will essentially only affect Ada.  OK
> > for the mainline?
>
> Ok.

Thanks.  It turns out that the patch was not complete, but the missing bits I 
can approve myself so installed as such.


        * stor-layout.c (place_field): Finalize non-constant offset for the
        field, if any.
ada/
        * gcc-interface/decl.c (create_field_decl_from): Finalize non-constant
        offset for the field, if any.



-- 
Eric Botcazou
Index: stor-layout.c
===================================================================
--- stor-layout.c	(revision 209334)
+++ stor-layout.c	(working copy)
@@ -1417,6 +1417,10 @@ place_field (record_layout_info rli, tre
   DECL_FIELD_BIT_OFFSET (field) = rli->bitpos;
   SET_DECL_OFFSET_ALIGN (field, rli->offset_align);
 
+  /* Evaluate nonconstant offsets only once, either now or as soon as safe.  */
+  if (TREE_CODE (DECL_FIELD_OFFSET (field)) != INTEGER_CST)
+    DECL_FIELD_OFFSET (field) = variable_size (DECL_FIELD_OFFSET (field));
+
   /* If this field ended up more aligned than we thought it would be (we
      approximate this by seeing if its position changed), lay out the field
      again; perhaps we can use an integral mode for it now.  */
Index: ada/gcc-interface/decl.c
===================================================================
--- ada/gcc-interface/decl.c	(revision 209334)
+++ ada/gcc-interface/decl.c	(working copy)
@@ -8443,7 +8443,8 @@ create_field_decl_from (tree old_field,
   if (!new_pos)
     {
       normalize_offset (&pos, &bitpos, offset_align);
-      DECL_FIELD_OFFSET (new_field) = pos;
+      /* Finalize the position.  */
+      DECL_FIELD_OFFSET (new_field) = variable_size (pos);
       DECL_FIELD_BIT_OFFSET (new_field) = bitpos;
       SET_DECL_OFFSET_ALIGN (new_field, offset_align);
       DECL_SIZE (new_field) = size;