Format C/C++ Code Using Clang-Format

Introduction

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.

Installation

$ 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.

.clang-format

---
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
BraceWrapping:
  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
ForEachMacros:
  - foreach
  - Q_FOREACH
  - BOOST_FOREACH
IncludeBlocks: Preserve
IncludeCategories:
  - 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 '.*\.\(cpp\|hpp\|cu\|cuh\|c\|h\)' -exec clang-format -style=file -i {} \;