bug#20629: 25.0.50; Regression: TAGS broken, can't find anything in C++ files.

[Eli Zaretskii]

> Date: Thu, 28 May 2015 15:12:38 +0200
> From: Francesco Potortì <pot@gnu.org>
> Cc: Eli Zaretskii <eliz@gnu.org>, 20629@debbugs.gnu.org
> 
> Francesco Potortì wrote:
> >> second, if appropriate, match against a tag ::NAME
> >> third, regex match against a tag .*::NAME$
> >
> >Why can we use colons? That implies some sort of knowledge about C++, 
> >whereas until now etags.el has remained language-agnostic.
> 
> Mh.  I had taken it for given that each major-mode in fact added
> something to the list of functions called when looking for a tag.
> Doesn't it work that way?

No.

In addition, doing so would not work if I tried to look up a symbol in
language A from a buffer whose major mode is tailored to language B.

> If not, couldn't it be done for languages where the
> language-agnostic behaviour of etags.el is not satisfactory?

etags.el relies on etags.c to know languages well enough to do that
part of the job.  I think we should keep this separation of
responsibilities.