一、YouCompleteMe介绍
YouCompleteMe(简称YCM)是一款vim的智能补全插件，支持
C/C++, Go, Python...等多种代码类型补全。它强大的功能吸引了不少人的使用，但有无数人因为安装它“折腰”，因为它的安装过程确实很麻烦。
花了一个下午的时间，来回装了两次，终于算是勉强搞定。
首先假定你已经安装好了vim和对应的插件管理器：升级安装vim 8.0并添加vundle插件管理
要注意的是，vim编辑器要求编译的时候添加了python支持。
根据测试，选择python2支持会比python3省事一些，因为后面安装cmake的时候貌似只能使用python2（具体是不是这样没有去深入研究，目前暂且按python2的来）。
先上一张效果图：
代码的主页为YouCompelteMe，先把代码拷贝到插件目录下：
git clone --recursive https://github.com/Valloric/YouCompleteMe.git ~/.vim/bundle/YouCompleteMe
git submodule update --init --recursive二、安装clang
clang下载地址，找到对应的二进制包下载：
wget http://releases.llvm.org/6.0.0/clang+llvm-6.0.0-x86_64-linux-gnu-ubuntu-14.04.tar.xz
tar -Jxvf clang+llvm-6.0.0-x86_64-linux-gnu-ubuntu-14.04.tar.xz -C /usr/local
ln -s /usr/local/clang+llvm-6.0.0-x86_64-linux-gnu-ubuntu-14.04/ /usr/local/clang需要用到的是libclang.so库文件，位于安装目录下的lib/libclang.so。
三、安装cmake
从源码编译安装：
wget https://cmake.org/files/v3.11/cmake-3.11.0-rc3.tar.gz
tar -zxvf cmake-3.11.0-rc3.tar.gz
cd cmake-3.11.0-rc3
./bootstrap
make && make install校验是否安装成功：
> cmake --version
cmake version 3.11.0-rc3
CMake suite maintained and supported by Kitware (kitware.com/cmake).四、编译ycm_core
建立一个临时文件夹~/ycm_build用来作为临时编译文件夹：
mkdir ~/ycm_build
cd ~/ycm_build使用cmake生成Makefile文件：
cmake -G "Unix Makefiles" -DEXTERNAL_LIBCLANG_PATH=/usr/local/clang/lib/libclang.so . ~/.vim/bundle/YouCompleteMe/third_party/ycmd/cpp问题一
如果安装vim时指定python的支持版本为python3，则在上面还要加上-DUSE_PYTHON2=OFF选项关掉默认使用python2编译。
否则安装完成后会出现以下错误：
The ycmd server SHUT DOWN (restart with '':YcmRestartServer'').
YCM core library compiled for Python 2 but loaded in Python 3.
Set the ''g:ycm_server_python_interpreter'' option to a Python 2 interpreter path.问题二
在ubuntu 16.04中执行这一步骤时遇到boost库缺失的问题：
CMake Warning at /usr/local/share/cmake-3.11/Modules/FindBoost.cmake:564 (message):
Imported targets and dependency information not available for Boost version
(all versions older than 1.33)
Call Stack (most recent call first):
/usr/local/share/cmake-3.11/Modules/FindBoost.cmake:903 (_Boost_COMPONENT_DEPENDENCIES)
/usr/local/share/cmake-3.11/Modules/FindBoost.cmake:1571 (_Boost_MISSING_DEPENDENCIES)
ycm/CMakeLists.txt:205 (find_package)
Please set them or make sure they are set and tested correctly in the CMake files:
Boost_INCLUDE_DIR (ADVANCED)
used as include directory in directory /home/ma/.vim/bundle/YouCompleteMe/third_party/ycmd/cpp/ycm
used as include directory in directory /home/ma/.vim/bundle/YouCompleteMe/third_party/ycmd/cpp/ycm
used as include directory in directory /home/ma/.vim/bundle/YouCompleteMe/third_party/ycmd/cpp/ycm
-- Configuring incomplete, errors occurred!
See also "/home/ma/ycm_build/CMakeFiles/CMakeOutput.log".解决方案：
sudo apt-get install build-essential g++ python-dev autotools-dev libicu-dev build-essential libbz2-dev libboost-all-dev 然后重新执行：
> cmake -G "Unix Makefiles" -DEXTERNAL_LIBCLANG_PATH=/usr/local/clang/lib/libclang.so . ~/.vim/bundle/YouCompleteMe/third_party/ycmd/cpp
# 以下为输出
-- The C compiler identification is GNU 5.4.0
-- The CXX compiler identification is GNU 5.4.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found PythonLibs: /usr/lib/x86_64-linux-gnu/libpython2.7.so (found suitable version "2.7.12", minimum required is "2.7")
-- Using libclang to provide semantic completion for C/C++/ObjC
-- Using external libclang: /usr/local/clang+llvm-6.0.0-x86_64-linux-gnu-ubuntu-14.04/lib/libclang.so.6.0
-- Configuring done
-- Generating done
-- Build files have been written to: /home/ma/ycm_build如果以上步骤都没有问题，开始下面的步骤
构建ycm_core：
cmake --build . --target ycm_core --config Release成功的结果：
五、配置
5.1 基础配置
cp ~/.vim/bundle/YouCompleteMe/third_party/ycmd/examples/.ycm_extra_conf.py ~/.vim/在~/.vimrc中添加配置：
添加插件支持，在vundle插件代码块中加入以下内容：
set rtp+=~/.vim/bundle/Vundle.vim
call vundle#begin()
Plugin ''VundleVim/Vundle.vim''
" 新加的YCM插件
Plugin ''Valloric/YouCompleteMe''
call vundle#end()然后添加配置文件：
"如果编译时指定的python版本为python3，这里也要改成对应的python版本
let g:ycm_server_python_interpreter=''/usr/bin/python''
let g:ycm_global_ycm_extra_conf=''~/.vim/.ycm_extra_conf.py''创建一个*.c文件测试：
5.2 其他配置
" 添加C++11 支持
let g:syntastic_cpp_compiler=''g++''
let g:syntastic_cpp_compiler_options=''std=c++11 -stdlib=libc++''
"离开插入模式后自动关闭预览窗口
set completeopt=longest,menu
autocmd InsertLeave * if pumvisible() == 0|pclose|endif
"回车即选中当前项
inoremap <expr> <CR> pumvisible() ? "\<C-y>" : "\<CR>"
inoremap <expr> <Down> pumvisible() ? "\<C-n>" : "\<Down>"
inoremap <expr> <Up> pumvisible() ? "\<C-p>" : "\<Up>"
inoremap <expr> <PageDown> pumvisible() ? "\<PageDown>\<C-p>\<C-n>" : "\<PageDown>"
inoremap <expr> <PageUp> pumvisible() ? "\<PageUp>\<C-p>\<C-n>" : "\<PageUp>"
"youcompleteme 默认tab s-tab 和自动补全冲突
"let g:ycm_key_list_select_completion=[''<c-n>'']
let g:ycm_key_list_select_completion = [''<Down>'']
"let g:ycm_key_list_previous_completion=[''<c-p>'']
let g:ycm_key_list_previous_completion = [''<Up>'']
"关闭加载.ycm_extra_conf.py提示
let g:ycm_confirm_extra_conf=0
" 开启 YCM 基于标签引擎
let g:ycm_collect_identifiers_from_tags_files=1
" 从第2个键入字符就开始罗列匹配项
let g:ycm_min_num_of_chars_for_completion=2
" 禁止缓存匹配项,每次都重新生成匹配项
let g:ycm_cache_omnifunc=0
" 语法关键字补全
let g:ycm_seed_identifiers_with_syntax=1
"force recomile with syntastic
nnoremap <F5> :YcmForceCompileAndDiagnostics<CR>
"nnoremap <leader>lo :lopen<CR> "open locationlist
"nnoremap <leader>lc :lclose<CR> "close locationlist
inoremap <leader><leader> <C-x><C-o>
"在注释输入中也能补全
let g:ycm_complete_in_comments = 1
"在字符串输入中也能补全
let g:ycm_complete_in_strings = 1
"注释和字符串中的文字也会被收入补全
let g:ycm_collect_identifiers_from_comments_and_strings = 0
let g:clang_user_options=''|| exit 0''
"nnoremap <leader>jd :YcmCompleter GoToDefinitionElseDeclaration<CR> " 跳转到定义处六、其他
6.1 C++头文件没有智能提示
添加都头文件目录到~/.vim/.ycm_extra_conf.py的flags数组中即可。
# 找到头文件所在的目录
> sudo find / -name iostream
/usr/include/c++/5/iostream
/usr/include/boost/tr1/tr1/iostream
/usr/local/clang+llvm-6.0.0-x86_64-linux-gnu-ubuntu-14.04/include/c++/v1/iostream
find: ‘/run/user/1000/gvfs’: Permission denied添加到flags数组：
flags=[
''...'',
''-isystem'',
''/usr/local/clang+llvm-6.0.0-x86_64-linux-gnu-ubuntu-14.04/include/c++/v1'',
]
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