bug#26928: 25.1; The xref-find-definitions cannot recognize the `tags' file generated by ctags

[palagend]

I use `ctags -R' command in the working directory `/usr/include',
generating a file named `tags' in the directory.And then I open one file in
`/usr/include' and then key in `M-x xref-find-definitions',the emacs
says that the tags file is not valid.




In GNU Emacs 25.1.1 (x86_64-redhat-linux-gnu, GTK+ Version 3.22.4)
 of 2016-12-15 built on buildvm-30.phx2.fedoraproject.org
Windowing system distributor 'Fedora Project', version 11.0.11903000
System Description:     Fedora release 25 (Twenty Five)

Configured using:
 'configure --build=x86_64-redhat-linux-gnu
 --host=x86_64-redhat-linux-gnu --program-prefix=
 --disable-dependency-tracking --prefix=/usr --exec-prefix=/usr
 --bindir=/usr/bin --sbindir=/usr/sbin --sysconfdir=/etc
 --datadir=/usr/share --includedir=/usr/include --libdir=/usr/lib64
 --libexecdir=/usr/libexec --localstatedir=/var
 --sharedstatedir=/var/lib --mandir=/usr/share/man
 --infodir=/usr/share/info --with-dbus --with-gif --with-jpeg --with-png
 --with-rsvg --with-tiff --with-xft --with-xpm --with-x-toolkit=gtk3
 --with-gpm=no --with-xwidgets build_alias=x86_64-redhat-linux-gnu
 host_alias=x86_64-redhat-linux-gnu 'CFLAGS=-DMAIL_USE_LOCKF -O2 -g
 -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2
 -fexceptions -fstack-protector-strong --param=ssp-buffer-size=4
 -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1
 -m64 -mtune=generic' LDFLAGS=-Wl,-z,relro
 PKG_CONFIG_PATH=:/usr/lib64/pkgconfig:/usr/share/pkgconfig'

Configured features:
XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND DBUS GCONF GSETTINGS NOTIFY
ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE M17N_FLT LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 XWIDGETS

Important settings:
  value of $LANG: zh_CN.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Help

Minor modes in effect:
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  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
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  global-font-lock-mode: t
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  auto-composition-mode: t
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  auto-compression-mode: t
  buffer-read-only: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
Checking 24 files in /usr/share/emacs/25.1/lisp/cedet...
Checking 57 files in /usr/share/emacs/25.1/lisp/calendar...
Checking 87 files in /usr/share/emacs/25.1/lisp/calc...
Checking 120 files in /usr/share/emacs/25.1/lisp/obsolete...
Checking for load-path shadows...done
Auto-saving...
Message modified; kill anyway? (y or n) y

Making completion list...
user-error: Previous command was not a yank

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Features:
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jka-compr thingatpt finder find-func lisp-mnt gnus-demon nntp gnus-group
gnus-undo gnus-start gnus-cloud nnimap nnmail mail-source tls gnutls
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mailabbrev gmm-utils mailheader gnus-win gnus gnus-ems nnheader
gnus-util mail-utils mm-util help-fns mail-prsvr wid-edit time linum
wheatgrass-theme finder-inf tex-site info package epg-config seq
byte-opt gv bytecomp byte-compile cl-extra help-mode easymenu cconv
cl-loaddefs pcase cl-lib time-date mule-util china-util tooltip eldoc
electric uniquify ediff-hook vc-hooks lisp-float-type mwheel x-win
term/common-win x-dnd tool-bar dnd fontset image regexp-opt fringe
tabulated-list newcomment elisp-mode lisp-mode prog-mode register page
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syntax facemenu font-core frame cl-generic cham georgian utf-8-lang
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cyrillic chinese charscript 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
dbusbind inotify dynamic-setting system-font-setting font-render-setting
xwidget-internal move-toolbar gtk x-toolkit x multi-tty
make-network-process emacs)

Memory information:
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