[PATCH v3] Add .clang-format style file

[Noah Goldstein]

On Wed, Mar 30, 2022 at 3:01 PM Florian Weimer <fw@deneb.enyo.de> wrote:
>
> * Noah Goldstein via Libc-alpha:
>
> > Went with version >= 11.0 since it covers most of the major features
> > and should be pretty universally accessibly.
> >
> > There are some issues:
> >
> > 1.  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. i.e:
> >     Desired:
> >     ```
> >     #ifndef A
> >     # define B
> >     #endif
> >     ```
> >     Options:
> >     ```
> >     #ifndef A
> >     #  define B /* Two spaces instead of one.  */
> >     #endif
> >
> >     #ifndef C
> >     #define D   /* No spaces.  */
> >     #endif
> >     ```
> >     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.
> >
> > 2.  concatenation of lines missing semi-colons:
> >     Throughout glibc there are macros used to setup aliasing that are
> >     outside of functions and don't end in semi-colons i.e:
> >     ```
> >     libc_hidden_def (__pthread_self)
> >     weak_alias (__pthread_self, pthread_self)
> >     ```
> >
> >     clang-format reformats lines like these to:
> >     ```
> >     libc_hidden_def (__pthread_self) weak_alias (__pthread_self, pthread_self)
> >     ```
> >
> >     which is generally undesirable.
> >
> > Other than those two big concerns there are certainly some questions
> > diffs but for the most part it creates a easy to read and consistent
> > style.
> > ---
> >  .clang-format | 175 ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 175 insertions(+)
> >  create mode 100644 .clang-format
> >
> > diff --git a/.clang-format b/.clang-format
> > new file mode 100644
> > index 0000000000..fcb344ef70
> > --- /dev/null
> > +++ b/.clang-format
> > @@ -0,0 +1,175 @@
> > +#  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 >= 11.0
> > +#
> > +#  For more information, see:
> > +#
> > +#   Documentation/process/clang-format.rst
>
> That's not a valid path in the glibc source tree.
>
> > +# BasedOnStyle:  GNU
>
> Why is this commented out?
>
> > +AccessModifierOffset: -2
> > +AlignAfterOpenBracket: Align
> > +AlignConsecutiveMacros: false
> > +AlignConsecutiveAssignments: false
> > +AlignConsecutiveBitFields: false
> > +AlignConsecutiveDeclarations: false
> > +AlignEscapedNewlines: Right
> > +AlignOperands:   true
> > +AlignTrailingComments: true
> > +AllowAllArgumentsOnNextLine: true
> > +AllowAllConstructorInitializersOnNextLine: true
> > +AllowAllParametersOfDeclarationOnNextLine: true
> > +AllowShortEnumsOnASingleLine: true
> > +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
> > +  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
> > +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
>
> These regular expression do not seem to be relevant to glibc.

Yeah. Will fix in v4.
>
> > +UseTab:          Never
>
> I prefer not using tabs, but others disagree, and most of the source
> files use tabs instead of 8 spaces (and not just for indentation).

+1 but yeah the consistent style seems to be tabs so will update in v4.
>
> > +ForEachMacros:
> > +  - 'FOR_EACH_IMPL'
> > +  - 'list_for_each'
> > +  - 'list_for_each_prev'
> > +  - 'list_for_each_prev_safe'
>
> If this is a YAML file, do these duplicate FoEachMacros keys have any
> effect?  Only the second one is relevant to glibc.

They all seem to have an effect.

What do you mean only the second is relevant? I see all but `list_for_each_prev`
used and `list_for_each_prev` appears to be defined so it could be used
to make a loop.