C/C++ Style Proposal

styles/C.md

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+## C and C++
+
+### Code Format and Style
+
+Generally, the source code should obey the style documented
+by [the configuration for clang-format](c-clang-format.yml).
+It's aimed to follow [NetBSD KNF](http://cvsweb.netbsd.org/bsdweb.cgi/src/share/misc/style?rev=HEAD&content-type=text/x-cvsweb-markup) loosely.
+
+However, there are a few exceptions.
+
+* We don't change the style of the imported code.
+  We try to keep local changes minimum.
+  Ideally, no local changes.
+
+* Notably, code imported from NuttX should obeys
+  [NuttX Coding Standard](https://cwiki.apache.org/confluence/display/NUTTX/Coding+Standard).
+
+### Tools
+
+The `clang-format` tool from LLVM 13 with the above mentioned configuration
+can be used to check and/or fix the style.
+
+#### NuttX Coding Standard
+
+The [nxstyle](https://github.com/apache/incubator-nuttx/blob/master/tools/nxstyle.c)
+tool can be used to check the style.

styles/c-clang-format.yml

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+Language: Cpp
+BasedOnStyle: LLVM
+IndentWidth: 8
+ConstructorInitializerIndentWidth: 8
+ContinuationIndentWidth: 8
+PointerAlignment: Right
+ColumnLimit: 79
+TabWidth: 8
+UseTab: ForContinuationAndIndentation
+AlignConsecutiveMacros: true
+AlwaysBreakAfterReturnType: TopLevelDefinitions
+ForEachMacros: ["TAILQ_FOREACH", "TAILQ_FOREACH_SAFE"]
+BreakBeforeBraces: Custom
+BraceWrapping:
+  AfterControlStatement: Never
+  AfterCaseLabel: false
+  AfterEnum: false
+  AfterFunction: true
+  AfterStruct: false
+  AfterUnion: false
+  AfterExternBlock: false
+  BeforeElse: false
+  BeforeWhile: false
+  SplitEmptyFunction: true
+AllowShortIfStatementsOnASingleLine: Never
+AllowShortLoopsOnASingleLine: false
+SpaceAfterCStyleCast: false
+SpaceAfterLogicalNot: false
+SortIncludes: true
+IndentCaseBlocks: true
+IndentCaseLabels: false
+IncludeBlocks: Regroup
+# Disable file-to-main-include by specifying a regex which never match
+IncludeIsMainRegex: '/INEXISTENT$'
+IncludeCategories:
+  - Regex: '<nuttx/.*'
+    Priority: 1
+  - Regex: '<sys/.*'
+    Priority: 2
+  # 3rd party libraries
+  - Regex: '<mbedtls/.*'
+    Priority: 4
+  - Regex: '<mqtt\.h>'
+    Priority: 4
+  - Regex: '<wasm_export.h>'
+    Priority: 4
+  # private fork of 3rd party libraries
+  - Regex: '"webclient/.*'
+    Priority: 5
+  - Regex: '"netlib/.*'
+    Priority: 5
+  - Regex: '"azure/.*'
+    Priority: 5
+  # system headers
+  - Regex: '<.*'
+    Priority: 3
+  - Regex: '".*'
+    Priority: 6
+  - Regex: '.*'
+    Priority: 7