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

["Jan Djärv" <jan.h.d@swipnet.se>]

This is the bad commit:

commit c7d601adefe130b773c1622a5aa8722d80709c1c
Author: Dmitry Gutov <dgutov@yandex.ru>
Date:   Sun May 10 00:36:46 2015 +0300

     Remove tag-symbol-match-p from etags-xref-find-definitions-tag-order

     * lisp/progmodes/etags.el (etags-xref-find-definitions-tag-order):
     Remove tag-symbol-match-p from the default value
     (http://lists.gnu.org/archive/html/emacs-devel/2015-05/msg00292.html).

The URL given in the description doesn't actually say why this change was 
made.  It just asks if anyone has objections.
So if there is no justification for this change, I will revert it soonish.
C++ support in Emacs is kind of a big deal.

	Jan D.

Den 2015-05-22 07:57, Jan D. skrev:
> Hello.
>
> Create this file as x.cc
> -----------------------------------------------------------------------
> class XX
> {
> public:
>      int foo();
>      void bar();
> };
>
> int
> XX::foo()
> {
>      return 1;
> }
>
> void
> XX::bar()
> {
>      foo();
> }
>
> int
> main(int argc, char *argv[])
> {
>      XX xx;
>      xx.bar();
>      return 0;
> }
>
> -----------------------------------------------------------------------
>
> Run etags on it:
>
> % etags x.cc
>
> In emacs, load the TAGS file, put the cursor on bar in xx.bar in main and
> press ESC .
> Emacs says: "No known definitions for: bar".
> Put cursor on foo in foo(); in XX::bar(), press ESC .
> Emacs says: "No known definitions for: foo".
>
> If you do the same thing in 24.5, it works as expected, i.e. the cursor
> jumps to respective member definition.
> The TAGS file produced by trunk etags and 24.5 etags are exactly the same.
>
> This regression makes the etags feature totally useless for C++.
>
>       Jan D.
>
>
>
>
> In GNU Emacs 25.0.50.1 (x86_64-apple-darwin14.3.0, NS appkit-1347.57 Version
> 10.10.3 (Build 14D136))
>   of 2015-05-22 on <anon>
> Windowing system distributor `Apple', version 10.3.1347
> Configured using:
>   `configure --enable-checking --verbose --with-ns --without-x CFLAGS=-g'
>
> Configured features:
> ACL LIBXML2 ZLIB
>
> Important settings:
>    value of $LC_COLLATE: C
>    value of $LANG: sv_SE.UTF-8
>    locale-coding-system: utf-8-unix
>
> Major mode: C++/l
>
> Minor modes in effect:
>    tooltip-mode: t
>    global-eldoc-mode: t
>    electric-indent-mode: t
>    mouse-wheel-mode: t
>    tool-bar-mode: t
>    menu-bar-mode: t
>    file-name-shadow-mode: t
>    global-font-lock-mode: t
>    font-lock-mode: t
>    blink-cursor-mode: t
>    auto-composition-mode: t
>    auto-encryption-mode: t
>    auto-compression-mode: t
>    line-number-mode: t
>    abbrev-mode: t
>
> Recent messages:
> For information about GNU Emacs and the GNU system, type C-h C-a.
> Starting a new list of tags tables
> user-error: No known definitions for: bar
> user-error: No known definitions for: foo
>
> Load-path shadows:
> None found.
>
> Features:
> (shadow sort gnus-util mail-extr emacsbug message dired format-spec
> rfc822 mml mml-sec mm-decode mm-bodies mm-encode mail-parse rfc2231
> mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
> mm-util help-fns mail-prsvr mail-utils etags thingatpt xref cl-seq ring
> eieio byte-opt gv bytecomp byte-compile cl-extra seq cconv eieio-core
> cl-loaddefs pcase cl-lib cc-mode cc-fonts easymenu cc-guess cc-menus
> cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs time-date mule-util
> tooltip eldoc electric uniquify ediff-hook vc-hooks lisp-float-type
> mwheel ns-win term/common-win tool-bar dnd fontset image regexp-opt
> fringe tabulated-list newcomment elisp-mode lisp-mode prog-mode register
> page menu-bar rfn-eshadow timer select scroll-bar mouse jit-lock
> font-lock syntax facemenu font-core frame cl-generic cham georgian
> utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao korean
> japanese eucjp-ms cp51932 hebrew greek romanian slovak czech european
> ethiopic indian cyrillic chinese case-table epa-hook jka-cmpr-hook help
> simple abbrev minibuffer cl-preloaded nadvice loaddefs button faces
> cus-face macroexp files text-properties overlay sha1 md5 base64 format
> env code-pages mule custom widget hashtable-print-readable backquote
> cocoa ns multi-tty make-network-process emacs)
>
> Memory information:
> ((conses 16 107206 5916)
>   (symbols 48 21504 1)
>   (miscs 40 49 143)
>   (strings 32 21487 4677)
>   (string-bytes 1 738790)
>   (vectors 16 15321)
>   (vector-slots 8 438795 3143)
>   (floats 8 151 24)
>   (intervals 56 245 4)
>   (buffers 976 13))
>
>