[v1] Add .clang-format style file

  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
  

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
>
  

On Tue, Mar 29, 2022 at 7:27 PM Fangrui Song <maskray@google.com> wrote:
>
> 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.

Fair enough. If linux is on 11.0+ that seems to be enough of a precedent.

Will post v2 with 11.0+ tomorrow so if anyone has a reason to stick with
9.0 they can comment.

>
> >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
> >