On 06/18/2014 11:38 AM, Mark Wielaard wrote:
> And a future version of DWARF might
> use the number for a completely different purpose.

The issue you linked says this:

   Remove DW_TAG_mutable_type from Appendix A (Figure 17)
   (Make sure not to reassign the number 0x3e to another tag.
    Perhaps we should leave the table entry in there with
    an "unused" marker in place of DW_TAG_mutable_type.

So it seems they intend to leave that number out forever.