一个几十人同时参与开发的C++项目，可以通过引入clang-tidy来帮助团队提升编码规范，可以讲题放到CI任务中，自动修复、检测一些常见问题，可以极大程度解放人力，并且缓解矛盾，总有一些人瞎写、记性差，长久训练也无法提升，只靠code review也要在这些人身上消耗大量人力，而且这些人通常还会不停的ping你，企图用上线时间迫使你放松一些，赶紧把他那些不用心的代码合进去。用一个冷冰冰的CI也可以很方便的堵住这些人的嘴。
下面是我基于clang-tidy的一些实践总结：
- 首先
clang-tidy基本处于能用、可用的状态，不完美，bug还不少，但是也基本足够了。 clang-tidy能够检查很大一部分低幼问题clang-tidy拥有自动修复模式(-fix)，但bug比较多，经常胡乱修复，下面案例中提供了一些我常用的配置项，这些项能够稳定自动修复。
我们需要用到的工具有：
clang-tidy二进制程序，编译安装llvm-project就可以得到，单线程程序、每次检测一个源码文件；run-clang-tidy.py脚本，貌似不会出现在llvm-project安装目录里，得从源码中拷贝出来。这个脚本主要并发执行N个clang-tidy进程；clang-tidy的配置(.ci/.clang-tidy)、脚手架脚本等
clang-tidy 配置
---
# 配置clang-tidy配置检测项，带'-'前缀的为disable对应的检测，否则为开启。这里主要是关闭一些用处不大，或者存在bug、假阳性的检查项
Checks: '*,
-llvm-*,
-llvmlibc-*,
-altera-*,
-android-*,
-boost-*,
-darwin-*,
-fuchsia-*,
-linuxkernel-*,
-objc-*,
-portability-*,
-zircon-*,
-clang-analyzer-osx*,
-clang-analyzer-optin.cplusplus.UninitializedObject,
-clang-analyzer-optin.cplusplus.VirtualCall,
-clang-analyzer-core.NullDereference,
-clang-analyzer-cplusplus.NewDelete,
-clang-analyzer-cplusplus.PlacementNew,
-clang-analyzer-cplusplus.NewDeleteLeaks,
-clang-analyzer-cplusplus.Move,
-clang-diagnostic-unused-parameter,
-cppcoreguidelines-*,
cppcoreguidelines-explicit-virtual-functions,
cppcoreguidelines-special-member-functions,
-cert-err58-cpp,
-cert-env33-c,
-cert-dcl37-c,
-cert-dcl51-cpp,
-google-runtime-int,
-google-readability-casting,
-google-readability-function-size,
-google-readability-todo,
-google-readability-braces-around-statements,
-google-build-using-namespace,
-readability-magic-numbers,
-readability-implicit-bool-conversion,
-readability-function-cognitive-complexity,
-readability-isolate-declaration,
-readability-convert-member-functions-to-static,
-readability-container-size-empty,
-readability-function-size,
-readability-qualified-auto,
-readability-make-member-function-const,
-readability-named-parameter,
-modernize-use-trailing-return-type,
-modernize-avoid-c-arrays,
-modernize-use-nullptr,
-modernize-replace-disallow-copy-and-assign-macro,
-modernize-use-bool-literals,
-modernize-use-equals-default,
-modernize-use-default-member-init,
-modernize-use-auto,
-modernize-loop-convert,
-modernize-deprecated-headers,
-modernize-raw-string-literal,
-misc-no-recursion,
-misc-unused-parameters,
-misc-redundant-expression,
-misc-non-private-member-variables-in-classes,
-hicpp-*,
hicpp-exception-baseclass,
-performance-no-int-to-ptr,
-bugprone-easily-swappable-parameters,
-bugprone-implicit-widening-of-multiplication-result,
-bugprone-integer-division,
-bugprone-exception-escape,
-bugprone-reserved-identifier,
-bugprone-branch-clone,
-bugprone-narrowing-conversions,
'
# 将警告转为错误
WarningsAsErrors: '*,-misc-non-private-member-variables-in-classes'
FormatStyle: file
# 过滤检查哪些头文件，clang-tidy会把源码依赖的头文件列出来都检查一遍，所以要屏蔽大量第三方库中的头文件
# 参考 https://stackoverflow.com/questions/71797349/is-it-possible-to-ignore-a-header-with-clang-tidy
# 该正则表达式引擎为llvm::Regex，支持的表达式较少，(?!xx)负向查找等都不支持
HeaderFilterRegex: '(xxx/include)*\.h$'
# 具体一些检查项的配置参数，可以参考的：
# https://github.com/envoyproxy/envoy/blob/main/.clang-tidy
# https://github.com/ClickHouse/ClickHouse/blob/d1d2f2c1a4979d17b7d58f591f56346bc79278f8/.clang-tidy
CheckOptions:
- key: readability-identifier-naming.ClassCase
value: CamelCase
- key: readability-identifier-naming.EnumCase
value: CamelCase
- key: readability-identifier-naming.LocalVariableCase
value: lower_case
- key: readability-identifier-naming.StaticConstantCase
value: aNy_CasE
- key: readability-identifier-naming.PrivateMemberCase
value: lower_case
- key: readability-identifier-naming.PrivateMemberSuffix
value: _
- key: readability-identifier-naming.ProtectedMethodCase
value: lower_case
- key: readability-identifier-naming.ProtectedMethodSuffix
value: _
- key: readability-braces-around-statements.ShortStatementLines
value: 2
- key: readability-uppercase-literal-suffix.NewSuffixes
value: 'f;u;ul'
# Ignore GoogleTest function macros.
- key: readability-identifier-naming.FunctionIgnoredRegexp
value: '(TEST|TEST_F|TEST_P|INSTANTIATE_TEST_SUITE_P|MOCK_METHOD|TYPED_TEST)'
- key: performance-move-const-arg.CheckTriviallyCopyableMove
value: 0
- key: cppcoreguidelines-special-member-functions.AllowSoleDefaultDtor
value: 1
- key: cppcoreguidelines-special-member-functions.AllowMissingMoveFunctions
value: 1
- key: cppcoreguidelines-special-member-functions.AllowMissingMoveFunctionsWhenCopyIsDeleted
value: 1
封装脚本：封装脚本将clang-tidy的2个模式封装成了2个函数，可以在CI环境中依次调用两个函数，其中auto_fix_simple_code是修复模式，clang_tidy_check_all是检查模式。
#!/bin/bash
function say() {
echo ">> $(date '+%Y-%m-%d %H:%M:%S') $*"
}
function cmd() {
say "@$*"
# shellcheck disable=SC2068
$@ 2>&1
}
function join_by() {
local IFS="$1"
shift
echo "$*"
}
function auto_fix_simple_code() {
# 可以被自动修复的检查项，下面是一些能够稳定修复的常见错误
AUTO_FIX_CHECKS_CFG=(
"-*"
"modernize-use-nullptr"
"modernize-use-override"
"modernize-use-using"
"modernize-make-shared"
"boost-use-to-string"
"readability-container-size-empty"
"readability-redundant-access-specifiers"
"readability-redundant-string-cstr"
"readability-redundant-string-init"
"readability-redundant-smartptr-get"
"readability-redundant-control-flow"
"google-readability-namespace-comments"
"performance-unnecessary-copy-initialization"
"performance-for-range-copy"
"performance-noexcept-move-constructor"
"clang-analyzer-deadcode.DeadStores"
)
AUTO_FIX_CHECKS=$(join_by "," "${AUTO_FIX_CHECKS_CFG[@]}")
#
run-clang-tidy.py -p "$BUILD_DIRECTORY" \
-checks="$AUTO_FIX_CHECKS" \
-fix $FILE \
> /tmp/clang-tidy-fix.log 2>&1
if [[ -n "${GITLAB_CI}" && "$(git status --short | wc -l)" != "0" ]]; then
set -e +o pipefail
# 存在被自动修复的变更，提交修复变更代码
cmd git add -u
cmd git commit -m "自动修复常规问题"
cmd git push "http://${CI_USER}:${CI_PRIVATE_TOKEN}@${CI_REPOSITORY_URL#*@}" "HEAD:${CI_MERGE_REQUEST_SOURCE_BRANCH_NAME}"
exit 0
fi
}
function clang_tidy_check_all() {
# 检查仍然存在的问题
say .ci/run-clang-tidy.py -p="$BUILD_DIRECTORY" \
-config-file=".ci/.clang-tidy" $FILE
.ci/run-clang-tidy.py -p="$BUILD_DIRECTORY" \
-config-file=".ci/.clang-tidy" $FILE \
> /tmp/clang-tidy-issue.log 2>&1
if [[ -n "${GITLAB_CI}" ]]; then
{
echo "clang-tidy 检测结果："
echo '```'
grep -A 2 -E "error:.*\[.*\]" /tmp/clang-tidy-issue.log
echo '```'
echo "详情请点击pipeline⭕️图标进行查看"
} > /tmp/clang-tidy-summary.log
if [[ $(wc -l < "/tmp/clang-tidy-summary.log") -gt 4 ]]; then
cmd add_comment "@/tmp/clang-tidy-summary.log" # add_comment 是CI中提供的一个命令，给对应MR中添加评论
exit 255 # 使CI任务失败
fi
else
{
echo "clang-tidy 检测结果："
echo '```'
grep -E "error:.*\[.*\]" /tmp/clang-tidy-issue.log | grep -Eo "\[.*\]" | sort | uniq -c | sort -n
echo '```'
echo "详情请点击pipeline⭕️图标进行查看"
} > /tmp/clang-tidy-summary.log
cat /tmp/clang-tidy-issue.log
fi
}
BUILD_DIRECTORY="./build" # cmake执行目录
SOURCE_DIRECTORY=${CI_PROJECT_DIR:-$(pwd)} # 源码目录
say "build cmake in $BUILD_DIRECTORY ..."
mkdir -p $BUILD_DIRECTORY
# 执行cmake build，-DCMAKE_EXPORT_COMPILE_COMMANDS=ON 使cmake生成单文件编译依赖配置文件，后续clang-tidy执行需要依赖该配置
# 会在cmake build目录下生成一个 compile_commands.jso n文件
cmd cd "$BUILD_DIRECTORY" \
&& cmd cmake "$SOURCE_DIRECTORY" -DCMAKE_BUILD_TYPE:STRING=RelWithDebInfo -DCMAKE_EXPORT_COMPILE_COMMANDS=ON
cmd cd "$SOURCE_DIRECTORY"
if [[ -n "${GITLAB_CI}" ]]; then # gitlab CI中会定义GITLAB_CI变量
# 运行在CI中
M_SHA1=$(git rev-parse origin/master)
# 过滤出本次MR中涉及修改的文件
FILE=$(git diff --name-status "$M_SHA1" | grep -E "^(M|A)\s+(include|src)/.*\.(cc|cpp|h|hpp)$" | awk '!/tests/ { print $2 }')
[[ "$FILE" == "" ]] && exit 0
else
# 手动执行
FILE='.*\.(?:h|cc)*'
fi
case "$1" in
fix)
auto_fix_simple_code
;;
check)
clang_tidy_check_all
;;
esac