[Bug c++/68711] [5 regression] SEGV on an invalid offsetof of a member of a virtual base

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68711

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-12-05
                 CC|                            |jason at redhat dot com
     Ever confirmed|0                           |1
      Known to fail|                            |6.0

--- Comment #1 from Martin Sebor <msebor at gcc dot gnu.org> ---
I suspect this is caused by the merge of the C++ delayed folding branch in
r230365 (CC'ing Jason).  The problem is in the function
build_class_member_access_expr().  The following otherwise untested change
restores the expected diagnostic:

--- gcc/cp/typeck.c     (revision 231314)
+++ gcc/cp/typeck.c     (working copy)
@@ -2358,8 +2358,14 @@
       int type_quals;
       tree member_type;

-      null_object_p = (INDIRECT_REF_P (object)
-                      && integer_zerop (TREE_OPERAND (object, 0)));
+      if (INDIRECT_REF_P (object))
+       {
+         tree oper = TREE_OPERAND (object, 0);
+         STRIP_NOPS (oper);
+         null_object_p = integer_zerop (oper);
+       }
+      else
+       null_object_p = false;

       /* Convert OBJECT to the type of MEMBER.  */
       if (!same_type_p (TYPE_MAIN_VARIANT (object_type),