bug#23164: 25.1.50; xref-find-definitions with local tags-file-name fails

[Johan Claesson <johanclaesson@bredband.net>]

I can also reproduce it on emacs-25 (commit f501116).
With valid TAGS file or /dev/zero.
I get the same backtrace.

Regards,

/Johan

Óscar Fuentes <ofv@wanadoo.es> writes:

> Dmitry Gutov <dgutov@yandex.ru> writes:
>
>> Thanks for the report, but that doesn't seem to be the case here. At
>> least if I replace "/dev/zero" with "~/vc/emacs/src/TAGS", the
>> scenario doesn't lead to an error (I just get "not found"), and if I
>> also use e.g. "CALLN" instead of "foo", the jump to the destination
>> occurs as expected.
>
> I can reproduce it here with an existing TAGS file, on emacs -Q.
>
> GNU Emacs 25.0.92.3 (x86_64-unknown-linux-gnu, X toolkit) of 2016-04-03
>
> at commit fc3cd53900eb5e80b91b6d2615b3800fd2f59c16
>
> Debugger entered--Lisp error: (wrong-type-argument stringp nil)
>   expand-file-name(nil)
>   tags-expand-table-name(nil)
>   visit-tags-table-buffer(t)
>   etags--xref-find-definitions("foo")
>   #[514 "\300!\207" [etags--xref-find-definitions] 4 "\n\n(fn BACKEND SYMBOL)"](etags "foo")
>   apply(#[514 "\300!\207" [etags--xref-find-definitions] 4 "\n\n(fn BACKEND SYMBOL)"] etags "foo")
>   xref-backend-definitions(etags "foo")
>   xref--find-xrefs("foo" definitions "foo" nil)
>   xref--find-definitions("foo" nil)
>   xref-find-definitions("foo")
>   eval((xref-find-definitions "foo") nil)
>   elisp--eval-last-sexp(nil)
>   eval-last-sexp(nil)
>   funcall-interactively(eval-last-sexp nil)
>   call-interactively(eval-last-sexp nil nil)
>   command-execute(eval-last-sexp)