Per http://wiki.dwarfstd.org/index.php?title=C%2B%2B0x:_Variadic_templates DW_TAG_GNU_formal_parameter_pack should have a DW_AT_name:

17$:      DW_TAG_formal_parameter_pack
              DW_AT_name("args")
18$:          DW_TAG_formal_parameter
                  ! no DW_AT_name attribute
                  DW_AT_type(reference to 13$)
(...)

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70536