[PATCH v1] Add .clang-format style file

[Fangrui Song]

On 2022-03-28, Noah Goldstein via Libc-alpha wrote:
>Went with version >= 9.0 since it covers most of the major features
>and should be pretty universally accessibly.

Why not 10.0?  clang-format 10.0.0 has been there for two years. Using
it will remove some clang-format >= 10.0 below. Related:
Linux kernel now requires Clang >= 11.0.
Since this patch introduces new tool, we can require higher versions.
Installing new clang-format isn't so difficult for old systems. There
are prebuilt packages even if the distro stops upgrading them.

>There are some issues, particularly indention of preprocessor
>directives. Unfortunately there doesn't appear to be a switch for
>a seperate 'IndentWidth' for preprocessor directives vs. normal
>code so we are stuck either not indenting the directives or
>over-indenting them. 

https://github.com/llvm/llvm-project/issues/42264
"Feature request: Two different indentation width options, one for code, one for pre-processor directives" :(

>Chose to over-indent as it generally seems easier
>to script halving all pre-processor indentations than counting the
>nested depth and indenting from scratch.

Yeah, I picked over-indent  for compiler-rt sanitizers as well
https://reviews.llvm.org/D100238

>Other than the pre-processor directives most of the changes it makes
>are cleaning up inconsistencies that already existed.
>---
> .clang-format | 164 ++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 164 insertions(+)
> create mode 100644 .clang-format
>
>diff --git a/.clang-format b/.clang-format
>new file mode 100644
>index 0000000000..121b475dbd
>--- /dev/null
>+++ b/.clang-format
>@@ -0,0 +1,164 @@
>+#  clang-format file for GLIBC
>+#  Copyright (C) 2022 Free Software Foundation, Inc.
>+#  This file is part of the GNU C Library.
>+#
>+#  The GNU C Library is free software; you can redistribute it and/or
>+#  modify it under the terms of the GNU Lesser General Public
>+#  License as published by the Free Software Foundation; either
>+#  version 2.1 of the License, or (at your option) any later version.
>+#
>+#  The GNU C Library is distributed in the hope that it will be useful,
>+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
>+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>+#  Lesser General Public License for more details.
>+#
>+#  You should have received a copy of the GNU Lesser General Public
>+#  License along with the GNU C Library; if not, see
>+#  <https://www.gnu.org/licenses/>.
>+#
>+#  Requires clang-format version >= 9.0
>+#
>+#  For more information, see:
>+#
>+#   Documentation/process/clang-format.rst
>+#   https://clang.llvm.org/docs/ClangFormat.html
>+#   https://clang.llvm.org/docs/ClangFormatStyleOptions.html
>+#
>+#  There are some known cases that this doesn't produce the desired
>+#  style (i.e Preprocessor Directives are over-indented and not
>+#  auto-commented). As a result, this is meant to be a utility to make
>+#  formatting easier, not a definitive standard.
>+---
>+# BasedOnStyle:  GNU
>+AccessModifierOffset: -2
>+AlignAfterOpenBracket: Align
>+AlignConsecutiveMacros: false
>+AlignConsecutiveAssignments: false
>+#AlignConsecutiveBitFields: false # clang-format >= 11.0
>+AlignConsecutiveDeclarations: false
>+AlignEscapedNewlines: Right
>+AlignOperands:   true
>+AlignTrailingComments: true
>+AllowAllArgumentsOnNextLine: true
>+AllowAllConstructorInitializersOnNextLine: true
>+AllowAllParametersOfDeclarationOnNextLine: true
>+#AllowShortEnumsOnASingleLine: true # clang-format >= 11.0
>+AllowShortBlocksOnASingleLine: false
>+AllowShortCaseLabelsOnASingleLine: false
>+AllowShortFunctionsOnASingleLine: All
>+AllowShortLambdasOnASingleLine: All
>+AllowShortIfStatementsOnASingleLine: Never
>+AllowShortLoopsOnASingleLine: false
>+AlwaysBreakAfterDefinitionReturnType: All
>+AlwaysBreakAfterReturnType: AllDefinitions
>+AlwaysBreakBeforeMultilineStrings: false
>+AlwaysBreakTemplateDeclarations: MultiLine
>+BinPackArguments: true
>+BinPackParameters: true
>+BraceWrapping:
>+  AfterCaseLabel:  true
>+  AfterClass:      true
>+  AfterControlStatement: true
>+  AfterEnum:       true
>+  AfterFunction:   true
>+  AfterNamespace:  true
>+  AfterStruct:     true
>+  AfterUnion:      true
>+  AfterExternBlock: true
>+  BeforeCatch:     true
>+  BeforeElse:      true
>+  #BeforeWhile:     true # clang-format >= 11.0
>+  IndentBraces:    true
>+  SplitEmptyFunction: true
>+  SplitEmptyRecord: true
>+  SplitEmptyNamespace: true
>+BreakBeforeBinaryOperators: All
>+BreakBeforeBraces: GNU
>+BreakBeforeInheritanceComma: false
>+BreakInheritanceList: BeforeColon
>+BreakBeforeTernaryOperators: true
>+BreakConstructorInitializersBeforeComma: false
>+BreakConstructorInitializers: BeforeColon
>+BreakStringLiterals: true
>+ColumnLimit:     79
>+CommentPragmas:  '^ IWYU pragma:'
>+CompactNamespaces: false
>+ConstructorInitializerAllOnOneLineOrOnePerLine: false
>+ConstructorInitializerIndentWidth: 4
>+ContinuationIndentWidth: 4
>+Cpp11BracedListStyle: false
>+#DeriveLineEnding: true # clang-format >= 10.0
>+DerivePointerAlignment: false
>+DisableFormat:   false
>+ExperimentalAutoDetectBinPacking: false
>+FixNamespaceComments: false
>+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: false
>+#IndentCaseBlocks: false # clang-format >= 11.0
>+#IndentGotoLabels: true # clang-format >= 10.0
>+IndentWidth:     2
>+IndentPPDirectives: AfterHash
>+#IndentExternBlock: AfterExternBlock # clang-format >= 11.0
>+IndentWrappedFunctionNames: false
>+#InsertTrailingCommas: None # clang-format >= 11.0
>+KeepEmptyLinesAtTheStartOfBlocks: true
>+MacroBlockBegin: ''
>+MacroBlockEnd:   ''
>+MaxEmptyLinesToKeep: 1
>+NamespaceIndentation: None
>+PenaltyBreakAssignment: 2
>+PenaltyBreakBeforeFirstCallParameter: 19
>+PenaltyBreakComment: 300
>+PenaltyBreakFirstLessLess: 120
>+PenaltyBreakString: 1000
>+PenaltyBreakTemplateDeclaration: 10
>+PenaltyExcessCharacter: 1000000
>+PenaltyReturnTypeOnItsOwnLine: 60
>+PointerAlignment: Right
>+ReflowComments:  true
>+SortIncludes:    false
>+SortUsingDeclarations: true
>+SpaceAfterCStyleCast: true
>+SpaceAfterLogicalNot: false
>+SpaceAfterTemplateKeyword: true
>+SpaceBeforeAssignmentOperators: true
>+SpaceBeforeCpp11BracedList: false
>+SpaceBeforeCtorInitializerColon: true
>+SpaceBeforeInheritanceColon: true
>+SpaceBeforeParens: Always
>+SpaceBeforeRangeBasedForLoopColon: true
>+#SpaceInEmptyBlock: false # clang-format >= 10.0
>+SpaceInEmptyParentheses: false
>+SpacesBeforeTrailingComments: 1
>+SpacesInAngles:  false
>+#SpacesInConditionalStatement: false # clang-format >= 10.0
>+SpacesInContainerLiterals: true
>+SpacesInCStyleCastParentheses: false
>+SpacesInParentheses: false
>+SpacesInSquareBrackets: false
>+#SpaceBeforeSquareBrackets: false # clang-format >= 10.0
>+Standard:        Cpp03
>+StatementMacros:
>+  - Q_UNUSED
>+  - QT_REQUIRE_VERSION
>+TabWidth:        8
>+UseTab:          Never
>+ForEachMacros:
>+  - 'FOR_EACH_IMPL'
>+  - 'list_for_each'
>+  - 'list_for_each_prev'
>+  - 'list_for_each_prev_safe'
>+...
>+
>-- 
>2.25.1
>