YouCompleteMe 是一个由前Google工程师Valloric开发的代码补全引擎,当前Vim和Emacs最强力的自动补全都基于YCMD。

YCM提供几乎所有主流编程语言的语义自动补全和代码跳转,包括C++。

不过YCM的C++补全需要额外设置才能工作,YCM必须知道编译器参数,如C++标准,Include目录等。单个项目的YCM配置保存在项目根目录下的.ycm_extra_conf.py

以下是我自己用的 Qt5 以及 CUDA 开发YCM配置

import os
import ycm_core
from clang_helpers import PrepareClangFlags

# Set this to the absolute path to the folder (NOT the file!) containing the
# compile_commands.json file to use that instead of 'flags'. See here for
# more details: http://clang.llvm.org/docs/JSONCompilationDatabase.html
# Most projects will NOT need to set this to anything; you can just change the
# 'flags' list of compilation flags. Notice that YCM itself uses that approach.
compilation_database_folder = ''

# These are the compilation flags that will be used in case there's no
# compilation database set.
flags = [
    '-DUSE_CLANG_COMPLETER',
    # THIS IS IMPORTANT! Without a "-std=<something>" flag, clang won't know which
    # language to use when compiling headers. So it will guess. Badly. So C++
    # headers will be compiled as C headers. You don't want that so ALWAYS specify
    # a "-std=<something>".
    # For a C project, you would set this to something like 'c99' instead of
    # 'c++11'.
    '-std=c++11',
    # ...and the same thing goes for the magic -x option which specifies the
    # language that the files to be compiled are written in. This is mostly
    # relevant for c++ headers.
    # For a C project, you would set this to 'c' instead of 'c++'.
    '-x',
    'c++',
    # Mac OS X specific flags.
    "-isystem", "/Library/Developer/CommandLineTools/usr/include/c++/v1",
    # Qt5 defines.
    "-DQT_CORE_LIB",
    "-DQT_GUI_LIB",
    "-DQT_NETWORK_LIB",
    "-DQT_QML_LIB",
    "-DQT_QUICK_LIB",
    "-DQT_SQL_LIB",
    "-DQT_WIDGETS_LIB",
    "-DQT_XML_LIB",
    "-fPIE",
    # Python include directories.
    "-I", "/usr/include/python2.7",
    # Qt5 header directories.
    "-I", "/usr/include",
    "-I", "/usr/include/qt",
    "-I", "/usr/lib/qt/mkspecs/linux-g++-64/qmake.conf",
    "-I", "/usr/include/qt/QtQuick",
    "-I", "/usr/include/qt/QtQml",
    "-I", "/usr/include/qt/QtNetwork",
    "-I", "/usr/include/qt/QtCore",
    "-I", "/usr/include/qt/QtGui",
    "-I", "/usr/include/qt/QtConcurrent",
    "-I", "/usr/include/qt/QtWidgets",
    "-I", "/usr/include/qt/QtXml",
    "-I", "/usr/include/qt/QtSql",
    # Local folder.
    "-I", "/usr/local/include",
    # CUDA header directories.
    "-I", "/usr/local/cuda/include",
    "-I", "./include",
    "-I", "./src",
    "-I", "./build/include",
]


if compilation_database_folder:
    database = ycm_core.CompilationDatabase( compilation_database_folder )
else:
    database = None


def DirectoryOfThisScript():
    return os.path.dirname( os.path.abspath( __file__ ) )


def MakeRelativePathsInFlagsAbsolute( flags, working_directory ):
    if not working_directory:
        return flags
    new_flags = []
    make_next_absolute = False
    path_flags = [ '-isystem', '-I', '-iquote', '--sysroot=' ]
    for flag in flags:
        new_flag = flag

        if make_next_absolute:
            make_next_absolute = False
            if not flag.startswith( '/' ):
                new_flag = os.path.join( working_directory, flag )

        for path_flag in path_flags:
            if flag == path_flag:
                make_next_absolute = True
                break

            if flag.startswith( path_flag ):
                path = flag[ len( path_flag ): ]
                new_flag = path_flag + os.path.join( working_directory, path )
                break

        if new_flag:
            new_flags.append( new_flag )

    return new_flags


def FlagsForFile( filename ):
    if database:
        # Bear in mind that compilation_info.compiler_flags_ does NOT return a
        # python list, but a "list-like" StringVec object
        compilation_info = database.GetCompilationInfoForFile( filename )
        final_flags = PrepareClangFlags(
            MakeRelativePathsInFlagsAbsolute(
                compilation_info.compiler_flags_,
                compilation_info.compiler_working_dir_ ),
            filename )

        # NOTE: This is just for YouCompleteMe; it's highly likely that your project
        # does NOT need to remove the stdlib flag. DO NOT USE THIS IN YOUR
        # ycm_extra_conf IF YOU'RE NOT 100% YOU NEED IT.
        try:
            final_flags.remove( '-stdlib=libc++' )
        except ValueError:
            pass
    else:
        relative_to = DirectoryOfThisScript()
        final_flags = MakeRelativePathsInFlagsAbsolute( flags, relative_to )

    return {
        'flags': final_flags,
        'do_cache': True
    }