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[Emacs] Auto runs clang-format when file save

yuu profile image yuu Updated on ・1 min read
  • Install via el-get
(el-get-bundle clang-format)
  • Hook
(add-hook 'c-mode-common-hook
          (function (lambda ()
                    (add-hook 'before-save-hook
  • Style configuration

.clang-format into project root directory.

My configuration below:

Language:        Cpp
# BasedOnStyle:  Google
AccessModifierOffset: -4
AlignAfterOpenBracket: Align
AlignConsecutiveAssignments: false
AlignConsecutiveDeclarations: false
AlignEscapedNewlinesLeft: true
AlignOperands:   true
AlignTrailingComments: true
AllowAllParametersOfDeclarationOnNextLine: true
AllowShortBlocksOnASingleLine: false
AllowShortCaseLabelsOnASingleLine: false
AllowShortFunctionsOnASingleLine: Inline
AllowShortIfStatementsOnASingleLine: false
AllowShortLoopsOnASingleLine: true
AlwaysBreakAfterDefinitionReturnType: None
AlwaysBreakAfterReturnType: None
AlwaysBreakBeforeMultilineStrings: true
AlwaysBreakTemplateDeclarations: true
BinPackArguments: true
BinPackParameters: true
  AfterClass:      false
  AfterControlStatement: false
  AfterEnum:       false
  AfterFunction:   false
  AfterNamespace:  false
  AfterObjCDeclaration: false
  AfterStruct:     false
  AfterUnion:      false
  BeforeCatch:     false
  BeforeElse:      false
  IndentBraces:    false
BreakBeforeBinaryOperators: None
BreakBeforeBraces: Attach
BreakBeforeTernaryOperators: true
BreakConstructorInitializersBeforeComma: true
BreakAfterJavaFieldAnnotations: false
BreakStringLiterals: true
ColumnLimit:     80
CommentPragmas:  '^ IWYU pragma:'
ConstructorInitializerAllOnOneLineOrOnePerLine: false
ConstructorInitializerIndentWidth: 4
ContinuationIndentWidth: 4
Cpp11BracedListStyle: true
DerivePointerAlignment: true
DisableFormat:   false
ExperimentalAutoDetectBinPacking: false
ForEachMacros:   [ foreach, Q_FOREACH, BOOST_FOREACH ]
  - Regex:           '^<.*\.h>'
    Priority:        1
  - Regex:           '^<.*'
    Priority:        2
  - Regex:           '.*'
    Priority:        3
IncludeIsMainRegex: '([-_](test|unittest))?$'
IndentCaseLabels: false
IndentWidth:     4
IndentWrappedFunctionNames: false
JavaScriptQuotes: Leave
JavaScriptWrapImports: true
KeepEmptyLinesAtTheStartOfBlocks: false
MacroBlockBegin: ''
MacroBlockEnd:   ''
MaxEmptyLinesToKeep: 1
NamespaceIndentation: None
ObjCBlockIndentWidth: 2
ObjCSpaceAfterProperty: false
ObjCSpaceBeforeProtocolList: false
PenaltyBreakBeforeFirstCallParameter: 1
PenaltyBreakComment: 300
PenaltyBreakFirstLessLess: 120
PenaltyBreakString: 1000
PenaltyExcessCharacter: 1000000
PenaltyReturnTypeOnItsOwnLine: 200
PointerAlignment: Left
ReflowComments:  true
SortIncludes:    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:        4
UseTab:          Never

Discussion (3)

Editor guide
ricardoaiglesias profile image
Ricardo Iglesias • Edited

Thanks for this guide!

I found that this configuration essentially forces the "before-save-hook" to always run "clang-format-buffer" once you load a C/C++ file. This is fine if you're working on a project, but has the unintended consequence of formatting non-C/C++ files if you work on many different files. This is particularly cumbersome when editing something like a LaTeX file, where the position of the curly braces and whitespace tends to matter.

A much more robust way I've found is to do simply map the "C-x C-s" key (which is the default save key) to a function that formats then saves:

(defun format-and-save()

  (kbd "C-x C-s")
thomas001 profile image
Thomas Weidner

I have the same problem. I solved it by doing

(add-hook 'c-common-mode-hook 
  (lambda ()
    (add-hook (make-local-variable 'before-save-hook)
yuu profile image
yuu Author

thank you both of them.
I will update for article and my init.el