为什么vim支持cscope而没有安装cscope？

Question

vim的版本信息：

root@lab:/home/mirror0/chrome# vim --version
VIM - Vi IMproved 7.2 (2008 Aug 9, compiled Jul 12 2010 12:48:02)
Included patches: 1-445
Modified by pkg-vim-maintainers@lists.alioth.debian.org
Compiled by buildd@
Huge version with GTK2-GNOME GUI.  Features included (+) or not (-):
+arabic +autocmd +balloon_eval +browse ++builtin_terms +byte_offset +cindent
+clientserver +clipboard +cmdline_compl +cmdline_hist +cmdline_info +comments
+cryptv +cscope +cursorshape +dialog_con_gui +diff +digraphs +dnd -ebcdic
+emacs_tags +eval +ex_extra +extra_search +farsi +file_in_path +find_in_path
+float +folding -footer +fork() +gettext -hangul_input +iconv +insert_expand
+jumplist +keymap +langmap +libcall +linebreak +lispindent +listcmds +localmap
+menu +mksession +modify_fname +mouse +mouseshape +mouse_dec +mouse_gpm
-mouse_jsbterm +mouse_netterm -mouse_sysmouse +mouse_xterm +multi_byte
+multi_lang -mzscheme +netbeans_intg -osfiletype +path_extra +perl +postscript
+printer +profile +python +quickfix +reltime +rightleft +ruby +scrollbind
+signs +smartindent -sniff +startuptime +statusline -sun_workshop +syntax
+tag_binary +tag_old_static -tag_any_white +tcl +terminfo +termresponse
+textobjects +title +toolbar +user_commands +vertsplit +virtualedit +visual
+visualextra +viminfo +vreplace +wildignore +wildmenu +windows +writebackup
+X11 -xfontset +xim +xsmp_interact +xterm_clipboard -xterm_save
   system vimrc file: "$VIM/vimrc"
     user vimrc file: "$HOME/.vimrc"
      user exrc file: "$HOME/.exrc"
  system gvimrc file: "$VIM/gvimrc"
    user gvimrc file: "$HOME/.gvimrc"
    system menu file: "$VIMRUNTIME/menu.vim"
  fall-back for $VIM: "/usr/share/vim"
Compilation: gcc -c -I. -Iproto -DHAVE_CONFIG_H -DFEAT_GUI_GTK  -pthread -I/usr/include/gtk-2.0 -I/usr/lib/gtk-2.0/include -I/usr/include/atk-1.0 -I/usr/include/cairo -I/usr/include/pango-1.0 -I/usr/include/gio-unix-2.0/ -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng12 -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include   -DORBIT2=1 -pthread -I/usr/include/libgnomeui-2.0 -I/usr/include/libart-2.0 -I/usr/include/gconf/2 -I/usr/include/gnome-keyring-1 -I/usr/include/libgnome-2.0 -I/usr/include/libbonoboui-2.0 -I/usr/include/libgnomecanvas-2.0 -I/usr/include/gtk-2.0 -I/usr/include/gnome-vfs-2.0 -I/usr/lib/gnome-vfs-2.0/include -I/usr/include/orbit-2.0 -I/usr/include/dbus-1.0 -I/usr/lib/dbus-1.0/include -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -I/usr/include/libbonobo-2.0 -I/usr/include/bonobo-activation-2.0 -I/usr/include/libxml2 -I/usr/include/pango-1.0 -I/usr/include/gail-1.0 -I/usr/include/freetype2 -I/usr/include/atk-1.0 -I/usr/lib/gtk-2.0/include -I/usr/include/cairo -I/usr/include/gio-unix-2.0/ -I/usr/include/pixman-1 -I/usr/include/libpng12     -Wall -g -O2    -D_REENTRANT -D_GNU_SOURCE -DDEBIAN  -fstack-protector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64  -I/usr/lib/perl/5.10/CORE  -I/usr/include/python2.6 -I/usr/include/tcl8.4  -D_REENTRANT=1  -D_THREAD_SAFE=1  -D_LARGEFILE64_SOURCE=1  -I/usr/lib/ruby/1.8/x86_64-linux -DRUBY_VERSION=18
Linking: gcc   -L.  -rdynamic -Wl,-export-dynamic  -Wl,-E  -Wl,--as-needed -o vim   -pthread -lgtk-x11-2.0 -lgdk-x11-2.0 -latk-1.0 -lpangoft2-1.0 -lgdk_pixbuf-2.0 -lpangocairo-1.0 -lcairo -lgio-2.0 -lpango-1.0 -lfreetype -lfontconfig -lgobject-2.0 -lgmodule-2.0 -lgthread-2.0 -lrt -lglib-2.0     -lgnomeui-2 -lbonoboui-2 -lgnomevfs-2 -lgnomecanvas-2 -lgnome-2 -lpopt -lbonobo-2 -lbonobo-activation -lORBit-2 -lart_lgpl_2 -lgtk-x11-2.0 -lgdk-x11-2.0 -latk-1.0 -lpangoft2-1.0 -lgdk_pixbuf-2.0 -lpangocairo-1.0 -lcairo -lgio-2.0 -lpango-1.0 -lfreetype -lfontconfig -lgconf-2 -lgmodule-2.0 -lgobject-2.0 -lgthread-2.0 -lrt -lglib-2.0   -lXt -lncurses -lselinux  -lacl -lgpm -Wl,-E  -fstack-protector -L/usr/local/lib  -L/usr/lib/perl/5.10/CORE -lperl -L/usr/lib/python2.6/config -lpython2.6 -lutil -Xlinker -export-dynamic -Wl,-O1 -Wl,-Bsymbolic-functions -L/usr/lib -ltcl8.4 -lieee -lruby1.8 -lrt -lm

vim支持cscope

root@lab:/home/mirror0/chrome# vim --version | grep cscope
+cryptv +cscope +cursorshape +dialog_con_gui +diff +digraphs +dnd -ebcdic

实际上，cscope命令没有安装。

root@lab:/home/mirror0/chrome# which cscope

那么，为什么vim支持cscope而没有安装cscope呢？

Answer 1

cscope支持有两个方面(类似于Perl、Python等语言支持)：

1. 在编译Vim期间，必须激活能够处理集成的程序代码，以便将功能包含在Vim可执行文件中。这就是:version所展示的。
2. 集成必须在安装Vim的系统上可用；也就是说，还必须有一个cscope可执行文件/ Perl共享库等，然后由Vim在发出相应命令时动态调用该库。当该部分丢失时，Vim将发出一个错误。