Configuring Style with clang-format¶

clang-format supports two ways to provide custom style options: directly specify style configuration in the -style= command line option or use -style=file and put style configuration in the .clang-format or _clang-format file in the project directory.

When using -style=file, clang-format for each input file will try to find the .clang-format file located in the closest parent directory of the input file. When the standard input is used, the search is started from the current directory.

The .clang-format file uses YAML format:

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

An easy way to get a valid .clang-format file containing all configuration options of a certain predefined style is:

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

When specifying configuration in the -style= option, the same configuration is applied for all input files. The format of the configuration is:

-style='{key1: value1, key2: value2, ...}'

Configuring Style in Code¶

When using clang::format::reformat(...) functions, the format is specified by supplying the clang::format::FormatStyle structure.

Configurable Format Style Options¶

This section lists the supported style options. Value type is specified for each option. For enumeration types possible values are specified both as a C++ enumeration member (with a prefix, e.g. LS_Auto), and as a value usable in the configuration (without a prefix: Auto).

BasedOnStyle (string)

The style used for all options not specifically set in the configuration.

This option is supported only in the clang-format configuration (both within -style='{...}' and the .clang-format file).

Possible values:

• 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

AccessModifierOffset (int)

The extra indent or outdent of access modifiers, e.g. public:.

AlignEscapedNewlinesLeft (bool)

If true, aligns escaped newlines as far left as possible. Otherwise puts them into the right-most column.

AlignTrailingComments (bool)

If true, aligns trailing comments.

AllowAllParametersOfDeclarationOnNextLine (bool)

Allow putting all parameters of a function declaration onto the next line even if BinPackParameters is false.

AllowShortIfStatementsOnASingleLine (bool)

If true, if (a) return; can be put on a single line.

AllowShortLoopsOnASingleLine (bool)

If true, while (true) continue; can be put on a single line.

AlwaysBreakBeforeMultilineStrings (bool)

If true, always break before multiline string literals.

AlwaysBreakTemplateDeclarations (bool)

If true, always break after the template<...> of a template declaration.

BinPackParameters (bool)

If false, a function call’s or function definition’s parameters will either all be on the same line or will have one line each.

BreakBeforeBinaryOperators (bool)

If true, binary operators will be placed after line breaks.

BreakBeforeBraces (BraceBreakingStyle)

The brace breaking style to use.

Possible values:

• BS_Attach (in configuration: Attach) Always attach braces to surrounding context.
• BS_Linux (in configuration: Linux) Like Attach, but break before braces on function, namespace and class definitions.
• BS_Stroustrup (in configuration: Stroustrup) Like Attach, but break before function definitions.
• BS_Allman (in configuration: Allman) Always break before braces.

BreakConstructorInitializersBeforeComma (bool)

Always break constructor initializers before commas and align the commas with the colon.

ColumnLimit (unsigned)

The column limit.

A column limit of 0 means that there is no column limit. In this case, clang-format will respect the input’s line breaking decisions within statements.

ConstructorInitializerAllOnOneLineOrOnePerLine (bool)

If the constructor initializers don’t fit on a line, put each initializer on its own line.

ConstructorInitializerIndentWidth (unsigned)

The number of characters to use for indentation of constructor initializer lists.

Cpp11BracedListStyle (bool)

If true, format braced lists as best suited for C++11 braced lists.

Important differences: - No spaces inside the braced list. - No line break before the closing brace. - Indentation with the continuation indent, not with the block indent.

Fundamentally, C++11 braced lists are formatted exactly like function calls would be formatted in their place. If the braced list follows a name (e.g. a type or variable name), clang-format formats as if the {} were the parentheses of a function call with that name. If there is no name, a zero-length name is assumed.

DerivePointerBinding (bool)

If true, analyze the formatted file for the most common binding.

ExperimentalAutoDetectBinPacking (bool)

If true, clang-format detects whether function calls and definitions are formatted with one parameter per line.

Each call can be bin-packed, one-per-line or inconclusive. If it is inconclusive, e.g. completely on one line, but a decision needs to be made, clang-format analyzes whether there are other bin-packed cases in the input file and act accordingly.

NOTE: This is an experimental flag, that might go away or be renamed. Do not use this in config files, etc. Use at your own risk.

IndentCaseLabels (bool)

Indent case labels one level from the switch statement.

When false, use the same indentation level as for the switch statement. Switch statement body is always indented one level more than case labels.

IndentFunctionDeclarationAfterType (bool)

If true, indent when breaking function declarations which are not also definitions after the type.

IndentWidth (unsigned)

The number of columns to use for indentation.

MaxEmptyLinesToKeep (unsigned)

The maximum number of consecutive empty lines to keep.

NamespaceIndentation (NamespaceIndentationKind)

The indentation used for namespaces.

Possible values:

• NI_None (in configuration: None) Don’t indent in namespaces.
• NI_Inner (in configuration: Inner) Indent only in inner namespaces (nested in other namespaces).
• NI_All (in configuration: All) Indent in all namespaces.

ObjCSpaceBeforeProtocolList (bool)

Add a space in front of an Objective-C protocol list, i.e. use Foo <Protocol> instead of Foo<Protocol>.

PenaltyBreakComment (unsigned)

The penalty for each line break introduced inside a comment.

PenaltyBreakFirstLessLess (unsigned)

The penalty for breaking before the first <<.

PenaltyBreakString (unsigned)

The penalty for each line break introduced inside a string literal.

PenaltyExcessCharacter (unsigned)

The penalty for each character outside of the column limit.

PenaltyReturnTypeOnItsOwnLine (unsigned)

Penalty for putting the return type of a function onto its own line.

PointerBindsToType (bool)

Set whether & and * bind to the type as opposed to the variable.

SpaceAfterControlStatementKeyword (bool)

If true, spaces will be inserted between ‘for’/’if’/’while’/... and ‘(‘.

SpaceBeforeAssignmentOperators (bool)

If false, spaces will be removed before assignment operators.

SpaceInEmptyParentheses (bool)

If false, spaces may be inserted into ‘()’.

SpacesBeforeTrailingComments (unsigned)

The number of spaces to before trailing line comments.

SpacesInCStyleCastParentheses (bool)

If false, spaces may be inserted into C style casts.

SpacesInParentheses (bool)

If true, spaces will be inserted after every ‘(‘ and before every ‘)’.

Standard (LanguageStandard)

Format compatible with this standard, e.g. use A<A<int> > instead of A<A<int>> for LS_Cpp03.

Possible values:

• LS_Cpp03 (in configuration: Cpp03) Use C++03-compatible syntax.
• LS_Cpp11 (in configuration: Cpp11) Use features of C++11 (e.g. A<A<int>> instead of A<A<int> >).
• LS_Auto (in configuration: Auto) Automatic detection based on the input.

TabWidth (unsigned)

The number of columns used for tab stops.

UseTab (UseTabStyle)

The way to use tab characters in the resulting file.

Possible values:

• UT_Never (in configuration: Never) Never use tab.
• UT_ForIndentation (in configuration: ForIndentation) Use tabs only for indentation.
• UT_Always (in configuration: Always) Use tabs whenever we need to fill whitespace that spans at least from one tab stop to the next one.

Examples¶

A style similar to the Linux Kernel style:

BasedOnStyle: LLVM
IndentWidth: 8
UseTab: Always
BreakBeforeBraces: Linux
AllowShortIfStatementsOnASingleLine: false
IndentCaseLabels: false

The result is (imagine that tabs are used for indentation here):

void test()
{
        switch (x) {
        case 0:
        case 1:
                do_something();
                break;
        case 2:
                do_something_else();
                break;
        default:
                break;
        }
        if (condition)
                do_something_completely_different();

        if (x == y) {
                q();
        } else if (x > y) {
                w();
        } else {
                r();
        }
}

A style similar to the default Visual Studio formatting style:

UseTab: Never
IndentWidth: 4
BreakBeforeBraces: Allman
AllowShortIfStatementsOnASingleLine: false
IndentCaseLabels: false
ColumnLimit: 0

The result is:

void test()
{
    switch (suffix)
    {
    case 0:
    case 1:
        do_something();
        break;
    case 2:
        do_something_else();
        break;
    default:
        break;
    }
    if (condition)
        do_somthing_completely_different();

    if (x == y)
    {
        q();
    }
    else if (x > y)
    {
        w();
    }
    else
    {
        r();
    }
}