clang-format配置说明

使用clang-format进行代码格式化时，可以使用预定义的样式之一(LLVM、Google、Chromium、Mozilla、WebKit、Microsoft )，也可以通过配置特定的样式选项来创建自定义样式，支持两种方式来提供自定义样式选项:在-style=命令行选项中直接指定样式配置，或者使用-style=file并将样式配置放在。项目目录中的clang-format或_clang-format文件。.clang-format文件遵循YAML格式配置，例如：

key1: value1
key2: value2
# A comment.
...

clang-format格式化文件时，它会使用文件名自动检测语言。当格式化标准输入或没有与其语言对应的扩展名的文件时，可以使用-assume-filename=选项来覆盖clang-format用来检测语言的文件名。

针对不同语言，可以在同一个clang-format文件中进行分别处理，如下：

---
# 默认遵循LLVM规则,但是缩进4列
BasedOnStyle: LLVM
IndentWidth: 4
---
Language: Cpp
# 强制C++的指针格式
DerivePointerAlignment: false
PointerAlignment: Left
---
Language: JavaScript
# Use 100 columns for JS.
ColumnLimit: 100
---
Language: Proto
# Don't format .proto files.
DisableFormat: true
---
Language: CSharp
# Use 100 columns for C#.
ColumnLimit: 100
...

可以通过以下方式，获取.clang-format的预定义样式,然后再根据实际要求进行相应的修改:

clang-format -style=llvm -dump-config > .clang-format

在当前文件生成.clang-format,内容如下:

---
Language:        Cpp
# BasedOnStyle:  Google
AccessModifierOffset: -1
AlignAfterOpenBracket: Align
AlignConsecutiveAssignments: false
AlignConsecutiveDeclarations: false
AlignEscapedNewlines: Left
AlignOperands:   true
AlignTrailingComments: true
AllowAllParametersOfDeclarationOnNextLine: true
AllowShortBlocksOnASingleLine: false
AllowShortCaseLabelsOnASingleLine: false
AllowShortFunctionsOnASingleLine: All
AllowShortIfStatementsOnASingleLine: true
AllowShortLoopsOnASingleLine: true
AlwaysBreakAfterDefinitionReturnType: None
AlwaysBreakAfterReturnType: None
AlwaysBreakBeforeMultilineStrings: true
AlwaysBreakTemplateDeclarations: true
BinPackArguments: true
BinPackParameters: true
BraceWrapping:   
  AfterClass:      false
  AfterControlStatement: false
  AfterEnum:       false
  AfterFunction:   false
  AfterNamespace:  false
  AfterObjCDeclaration: false
  AfterStruct:     false
  AfterUnion:      false
  AfterExternBlock: false
  BeforeCatch:     false
  BeforeElse:      false
  IndentBraces:    false
  SplitEmptyFunction: true
  SplitEmptyRecord: true
  SplitEmptyNamespace: true
BreakBeforeBinaryOperators: None
BreakBeforeBraces: Attach
BreakBeforeInheritanceComma: false
BreakBeforeTernaryOperators: true
BreakConstructorInitializersBeforeComma: false
BreakConstructorInitializers: BeforeColon
BreakAfterJavaFieldAnnotations: false
BreakStringLiterals: true
ColumnLimit:     80
CommentPragmas:  '^ IWYU pragma:'
CompactNamespaces: false
ConstructorInitializerAllOnOneLineOrOnePerLine: true
ConstructorInitializerIndentWidth: 4
ContinuationIndentWidth: 4
Cpp11BracedListStyle: true
DerivePointerAlignment: true
DisableFormat:   false
ExperimentalAutoDetectBinPacking: false
FixNamespaceComments: true
ForEachMacros:   
  - foreach
  - Q_FOREACH
  - BOOST_FOREACH
IncludeBlocks:   Preserve
IncludeCategories: 
  - Regex:           '^<ext/.*\.h>'
    Priority:        2
  - Regex:           '^<.*\.h>'
    Priority:        1
  - Regex:           '^<.*'
    Priority:        2
  - Regex:           '.*'
    Priority:        3
IncludeIsMainRegex: '([-_](test|unittest))?$'
IndentCaseLabels: true
IndentPPDirectives: None
IndentWidth:     2
IndentWrappedFunctionNames: false
JavaScriptQuotes: Leave
JavaScriptWrapImports: true
KeepEmptyLinesAtTheStartOfBlocks: false
MacroBlockBegin: ''
MacroBlockEnd:   ''
MaxEmptyLinesToKeep: 1
NamespaceIndentation: None
ObjCBlockIndentWidth: 2
ObjCSpaceAfterProperty: false
ObjCSpaceBeforeProtocolList: false
PenaltyBreakAssignment: 2
PenaltyBreakBeforeFirstCallParameter: 1
PenaltyBreakComment: 300
PenaltyBreakFirstLessLess: 120
PenaltyBreakString: 1000
PenaltyExcessCharacter: 1000000
PenaltyReturnTypeOnItsOwnLine: 200
PointerAlignment: Left
RawStringFormats: 
  - Delimiter:       pb
    Language:        TextProto
    BasedOnStyle:    google
ReflowComments:  true
SortIncludes:    true
SortUsingDeclarations: true
SpaceAfterCStyleCast: false
SpaceAfterTemplateKeyword: true
SpaceBeforeAssignmentOperators: true
SpaceBeforeParens: ControlStatements
SpaceInEmptyParentheses: false
SpacesBeforeTrailingComments: 2
SpacesInAngles:  false
SpacesInContainerLiterals: true
SpacesInCStyleCastParentheses: false
SpacesInParentheses: false
SpacesInSquareBrackets: false
Standard:        Auto
TabWidth:        8
UseTab:          Never
...

下面针对每一条内容进行说明。

BasedOnStyle : 用于配置中未专门设置的所有选项的样式。可选项包括:

• LLVM A style complying with the LLVM coding standards
• Google A style complying with Google’s C++ style guide
• Chromium A style complying with Chromium’s style guide
• Mozilla A style complying with Mozilla’s style guide
• WebKit A style complying with WebKit’s style guide
• Microsoft A style complying with Microsoft’s style guide
• GNU A style complying with the GNU coding standards
• InheritParentConfig Not a real style, but allows to use the .clang-format file from the parent directory (or its parent if there is none). If there is no parent file found it falls back to the fallback style, and applies the changes to that.

AccessModifierOffset :访问修饰符的额外缩进或突出 例如:public、private等

AlignAfterOpenBracket :左括号后水平对齐参数。可能值包括:

• BAS _ Align(配置值:Align)在左括号上对齐参数(AlignAfterOpenBracket: Align)
• BAS_DontAlign (配置值: DontAlign)不对齐参数，采用ContinuationIndentWidth的值进行缩进
• BAS_AlwaysBreak(配置值:AlwaysBreak) 如果参数不在一行中，总是在左括号后断开

AlignArrayOfStructures :如果不是None，则对结构数组使用初始化时，将字段与列对齐。可能取值:

• AIAS_Left (配置值: Left) 左对齐列
• AIAS_Right(配置值: Right) 右对齐列

AlignConsecutiveAssignments :对齐连续分配的样式

.....