GDB and -gdwarf-5

I have GCC 6.3.0 installed, and it seems to support DWARF2 version 5
via the -gdwarf-5 switch.  But I wanted to make sure I really get that
version of debug info, so I tried "info source" in GDB.  But that
command doesn't tell the version of DWARF2.  Is there a GDB command
which does?

I also tried "objdump --dwarf=info" (Binutils 2.29), but that says the
DWARF2 version is 4.  So now I'm confused.

Can someone please tell me how to verify the version of DWARF2 I get
with that GCC switch?

Thanks.