Is there a recursive debug_c_tree which decodes "variant tag"?

[Larry Evans <cppljevans at suddenlink dot net>]

While attempting to debug the compiler on:

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40092

I'm having great difficulty understanding the output
of debug_c_tree or debug_tree because the child
tree's are not shown.  The ddd debugger:

  http://www.gnu.org/software/ddd/

is some help; however, even there it's unclear
what the tree looks like because the tree is
some sort of variant and ddd apparently doesn't
know how to interpret the variant's tag.  Instead,
I have to trial and error what the variant is
and mostly miss the mark.

Is there any such debug_tree function usable in
gdb or ddd which will show the actual tree
variant?