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Lei Mao

Machine Learning, Artificial Intelligence, Computer Science.

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In a collaborative project, code formatting software, such as Clang-Format, have been widely used to make sure that the code written by different people have uniform style and format. I have just learned some basic usages of Clang-Format and documented them in this blog post.


$ sudo apt-get install clang-format

Format Configuration

In order to format our code, we need a configuration file .clang-format. This file could be generated from some pre-configured styles.

To generate .clang-format from style llvm, run the following command in the terminal.

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

Other candidate styles include google, chromium, mozilla, webkit, microsoft.

We could further modify the .clang-format file using our preferences. Below is my modified format file. More style examples could be found from Clang documentations.

Language:        Cpp
# BasedOnStyle:  LLVM
AccessModifierOffset: -4 # -2
AlignAfterOpenBracket: Align
AlignConsecutiveAssignments: false
AlignConsecutiveDeclarations: false
AlignEscapedNewlines: Right
AlignOperands:   true
AlignTrailingComments: true
AllowAllParametersOfDeclarationOnNextLine: true
AllowShortBlocksOnASingleLine: false
AllowShortCaseLabelsOnASingleLine: false
AllowShortFunctionsOnASingleLine: All
AllowShortIfStatementsOnASingleLine: false
AllowShortLoopsOnASingleLine: false
AlwaysBreakAfterDefinitionReturnType: None
AlwaysBreakAfterReturnType: None
AlwaysBreakBeforeMultilineStrings: false
AlwaysBreakTemplateDeclarations: true # false
BinPackArguments: true
BinPackParameters: true
  AfterClass:      true # false
  AfterControlStatement: true # false
  AfterEnum:       true # false
  AfterFunction:   true # false
  AfterNamespace:  true # false
  AfterObjCDeclaration: true # false
  AfterStruct:     true # false
  AfterUnion:      true # false
  AfterExternBlock: true # false
  BeforeCatch:     true # false
  BeforeElse:      true # false
  IndentBraces:    true # false
  SplitEmptyFunction: true
  SplitEmptyRecord: true
  SplitEmptyNamespace: true
BreakBeforeBinaryOperators: None
BreakBeforeBraces: Allman # Attach
BreakBeforeInheritanceComma: false
BreakBeforeTernaryOperators: true
BreakConstructorInitializersBeforeComma: false
BreakConstructorInitializers: BeforeColon
BreakAfterJavaFieldAnnotations: false
BreakStringLiterals: true
ColumnLimit:     80
CommentPragmas:  '^ IWYU pragma:'
CompactNamespaces: false
ConstructorInitializerAllOnOneLineOrOnePerLine: false
ConstructorInitializerIndentWidth: 4
ContinuationIndentWidth: 4
Cpp11BracedListStyle: true
DerivePointerAlignment: false
DisableFormat:   false
ExperimentalAutoDetectBinPacking: false
FixNamespaceComments: true
  - foreach
IncludeBlocks:   Preserve
  - Regex:           '^"(llvm|llvm-c|clang|clang-c)/'
    Priority:        2
  - Regex:           '^(<|"(gtest|gmock|isl|json)/)'
    Priority:        3
  - Regex:           '.*'
    Priority:        1
IncludeIsMainRegex: '(Test)?$'
IndentCaseLabels: true # false
IndentPPDirectives: None
IndentWidth:   4  #2
IndentWrappedFunctionNames: false
JavaScriptQuotes: Leave
JavaScriptWrapImports: true
KeepEmptyLinesAtTheStartOfBlocks: true
MacroBlockBegin: ''
MacroBlockEnd:   ''
MaxEmptyLinesToKeep: 1
NamespaceIndentation: None
ObjCBlockIndentWidth: 2
ObjCSpaceAfterProperty: false
ObjCSpaceBeforeProtocolList: true
PenaltyBreakAssignment: 2
PenaltyBreakBeforeFirstCallParameter: 19
PenaltyBreakComment: 300
PenaltyBreakFirstLessLess: 120
PenaltyBreakString: 1000
PenaltyExcessCharacter: 1000000
PenaltyReturnTypeOnItsOwnLine: 60
PointerAlignment: Left # Right
ReflowComments:  true
SortIncludes:    true
SortUsingDeclarations: true
SpaceAfterCStyleCast: false
SpaceAfterTemplateKeyword: true
SpaceBeforeAssignmentOperators: true
SpaceBeforeParens: ControlStatements
SpaceInEmptyParentheses: false
SpacesBeforeTrailingComments: 1
SpacesInAngles:  false
SpacesInContainerLiterals: true
SpacesInCStyleCastParentheses: false
SpacesInParentheses: false
SpacesInSquareBrackets: false
Standard:        Cpp11
TabWidth:        8
UseTab:          Never

Run Code Formatting

Clang-Format could format a single file or all files with the same file extension. For example, to format .cpp extension, run the following command in the terminal.

$ clang-format -i *.cpp

To format all .h, .c, .hpp, .cpp, .cu files together, run the following command in the terminal.

$ find . -regex '.*\.\(cpp\|hpp\|cu\|c\|h\)' -exec clang-format -style=file -i {} \;