[PATCH v1] Add .clang-format style file

[Noah Goldstein]

Went with version >= 9.0 since it covers most of the major features
and should be pretty universally accessibly.

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. 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.

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