    GC_API int GC_CALL GC_get_stack_base(struct GC_stack_base *sb)
    {
      ptr_t trunc_sp;
      word size;

      /* Set page size if it is not ready (so client can use this       */
      /* function even before GC is initialized).                       */
      if (!GC_page_size) GC_setpagesize();

      trunc_sp = (ptr_t)((word)GC_approx_sp() & ~(GC_page_size - 1));
      /* FIXME: This won't work if called from a deeply recursive       */
      /* client code (and the committed stack space has grown).         */
      size = GC_get_writable_length(trunc_sp, 0);
      GC_ASSERT(size != 0);
      sb -> mem_base = trunc_sp + size;
      return GC_SUCCESS;
    }
    GC_API int GC_CALL GC_get_stack_base(struct GC_stack_base *sb)
    {
      ptr_t trunc_sp;
      word size;

       
       
      if (!GC_page_size) GC_setpagesize();

      trunc_sp = (ptr_t)((word)GC_approx_sp() & ~(GC_page_size - 1));
       
       
      size = GC_get_writable_length(trunc_sp, 0);
      GC_ASSERT(size != 0);
      sb -> mem_base = trunc_sp + size;
      return GC_SUCCESS;
    }