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Subject: [Bug bootstrap/55792] [4.8 Regression] Bad memory access with profiledbootstrap and LTO
Date: Mon, 07 Jan 2013 17:55:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55792

--- Comment #11 from Diego Novillo <dnovillo at gcc dot gnu.org> 2013-01-07 17:54:14 UTC ---
(In reply to comment #9)
> Eh.  Diego, how does GTY((user)) work here?  It smells like a bug in vec.h
> to me.
> 
> /* Garbage collection support for vec<T, A, vl_embed>.  */
> 
> template<typename T>
> void
> gt_ggc_mx (vec<T, va_gc> *v)
> {
>   extern void gt_ggc_mx (T &);
>   for (unsigned i = 0; i < v->length (); i++)
>     gt_ggc_mx ((*v)[i]);
> }
> 
> doesn't it need to mark the vec itself?  Maybe automatic registration of
> roots (this is a GC root) does not work with GTY((user))?

No.  The root is/should be marked by the code calling gt_ggc_mx.  gengtype will
generate code like:

  if (ggc_test_and_set_mark (x))
    {
      gt_ggc_mx (x);
    }

ggc_test_and_set_mark() is the one that marks the root.  Has gengtype generated
a function for this global?  It should be something like this

void
gt_ggc_mx_vec_<mangled_type_name> (void *x_p)
{
  vec<type_name,va_gc> * const x = (vec<type_name,va_gc> *)x_p;
  if (ggc_test_and_set_mark (x))
    {
      gt_ggc_mx (x);
    }
}