SERVER-18579: Add .clang-format & Scons support

SConstruct

@@ -2230,6 +2230,10 @@ checkErrorCodes()
 # --- lint ----
 
 def doLint( env , target , source ):
+    import buildscripts.clang_format
+    if not buildscripts.clang_format.lint(None, []):
+        raise Exception("clang-format lint errors")
+
     import buildscripts.lint
     if not buildscripts.lint.run_lint( [ "src/mongo/" ] ):
         raise Exception( "lint errors" )

etc/format_sample.cpp

@@ -0,0 +1,171 @@
+/**
+ * Sample file to demonstrate various clang-format messages
+ */
+#include <stdio.h>
+#include <vector>
+#include <string>
+
+// NamespaceIndentation: None
+namespace foo {
+// Contents of namespace are not indented.
+int foo;
+
+namespace bar {
+int bar;
+
+namespace {
+int anony;
+}  // namespace anony
+
+}  // namespace bar
+
+/**
+ * A Class comment
+ */
+class Example {
+    // AccessModiferOffset: -4
+public:
+    // BreakConstructorInitializersBeforeComma: false
+    // ConstructorInitializerAllOnOneLineOrOnePerLine: true
+    //
+    Example() : _aVariable(4), _bVariable(42) {}
+    Example(int a)
+        : _aVariable(a),
+          _bVariable(42),
+          _AReallyReallyLongVariableName(4),
+          _AnotherReallyReallyLongVariableNameToTriggerWrapping(42) {
+        printf("Hello ");
+    }
+    ~Example() {}
+
+    /**
+     * A Function comment
+     * AllowShortFunctionsOnASingleLine: Empty
+     */
+    int getOneLineFunction() {
+        return 0;
+    }
+
+    /** A Incorrect Function comment
+     * AllowShortFunctionsOnASingleLine: Empty
+     */
+    void doNothing() {}
+
+    /**
+     * A Useful Function comment
+     */
+    int manyVariableFunction(unsigned long long arg1, char arg2, unsigned long long arg3);
+
+private:
+    int _aVariable;
+    long _bVariable;
+    short _cVarianble = 49;
+    long _AReallyReallyLongVariableName;
+    long _AnotherReallyReallyLongVariableNameToTriggerWrapping;
+};
+
+int foo3() {
+    return 42;
+}
+
+// AlwaysBreakTemplateDeclarations: true
+template <typename T>
+T myAdd(T x, T y) {
+    return x + y;
+}
+
+// AlwaysBreakAfterDefinitionReturnType: false
+// BinPackParameters: false
+int Example::manyVariableFunction(unsigned long long argWithLongName,
+                                  char arg2,
+                                  unsigned long long argWithAnotherLongName) {
+    // 3.7 - AlignConsecutiveAssignments - false
+    //
+    int aaaa = 12;
+    int b = 23;
+    int ccc = 23;
+    // PointerAlignment: Left
+    const char* some_pointer = "Hello";
+
+    // SpacesInAngles: false
+    std::vector<std::pair<std::string, int>> list;
+
+    // SpaceAfterCStyleCast: false
+    // SpacesInCStyleCastParentheses: false
+    char* some_nonconst_pointer = (char*)some_pointer;
+
+    // Multi-line if
+    // SpaceBeforeParens: False
+    if (argWithLongName == 0) {  // Comment: SpacesBeforeTrailingComments
+        // Do something
+    } else if (b % 7 = 3) {
+    }  // some weird trailing else comment that clang-format does not touch
+    else {
+        // Notice the indent around else
+    }
+
+    // AllowShortIfStatementsOnASingleLine: false
+    // Put statements on separate lines for short ifs
+    if (arg2 == 'a')
+        arg2 = 'b';
+
+    int bbbbbbbbbbbbbbbbbbbbbbbbbbbb, cccccccccccccccccccccccccccccc;
+    int aaaaaaaaaaaaaaaaaaaaaaaaaaaa =
+        bbbbbbbbbbbbbbbbbbbbbbbbbbbb + cccccccccccccccccccccccccccccc;
+
+    // AlignOperands
+    int dddddddddddddddddddddddddddd = aaaaaaaaaaaaaaaaaaaaaaaaaaaa * 7 + 4 % 235124 > 275645
+        ? bbbbbbbbbbbbbbbbbbbbbbbbbbbb + 897234
+        : cccccccccccccccccccccccccccccc % 1293402;
+
+    // AllowShortBlocksOnASingleLine: false
+    if (b) {
+        return 3;
+    }
+
+    // AllowShortLoopsOnASingleLine: false
+    while (b < 5)
+        b++;
+
+    // BreakBeforeBinaryOperators: None
+    if (b > 5 || b % 42 || cccccccccccccccccccccccccccccc % 873 || aaaa * 12312 % 23485 != 9873 ||
+        some_pointer != 0) {
+        printf("Huh!\n");
+    }
+
+    // AlignAfterOpenBracket: false
+    // BinPackParameters: false
+    printf("A short function call %s %s %d - %ld\n", "", "tgz", 4, ULONG_MAX);
+    printf("A long function call %s %s %d - %ld\n",
+           "http://www.mongodbo.org/downloads",
+           "mongodb-latest.tgz",
+           4,
+           ULONG_MAX);
+    printf("Thing1 %s\n", "Thing2");
+
+    // No spaces between parens and args
+    printf("%c\n", arg2);
+
+    // A switch statement: TODO: Andy, what is the indent we want? Google style?
+    switch (arg2) {
+        // AllowShortCaseLabelsOnASingleLine: false
+        // IndentCaseLabels: true
+        case 'a':
+            return 2;
+        case 'y':
+        case 'z':
+            // Do something here
+            break;
+        default:
+            // The default`
+            break;
+    }
+
+    do {
+        // Do a loop here
+    } while (0);
+
+    return 1;
+}
+
+}  // namespace foo

src/mongo/.clang-format

@@ -0,0 +1,61 @@
+# BasedOnStyle:  Google
+AccessModifierOffset: -4
+AlignOperands: false
+AlignAfterOpenBracket: true
+AlignEscapedNewlinesLeft: true
+AlignTrailingComments: true
+AllowAllParametersOfDeclarationOnNextLine: true
+AllowShortBlocksOnASingleLine: false
+AllowShortCaseLabelsOnASingleLine: false
+AllowShortFunctionsOnASingleLine: Empty
+AllowShortIfStatementsOnASingleLine: false
+AllowShortLoopsOnASingleLine: false
+AlwaysBreakAfterDefinitionReturnType: false
+AlwaysBreakBeforeMultilineStrings: true
+AlwaysBreakTemplateDeclarations: true
+BinPackArguments: false
+BinPackParameters: false
+BreakBeforeBinaryOperators: None
+BreakBeforeBraces: Attach
+BreakBeforeTernaryOperators: true
+BreakConstructorInitializersBeforeComma: false
+ColumnLimit:     100
+CommentPragmas:  ''
+ConstructorInitializerAllOnOneLineOrOnePerLine: true
+ConstructorInitializerIndentWidth: 4
+ContinuationIndentWidth: 4
+Cpp11BracedListStyle: true
+DerivePointerAlignment: false
+DisableFormat:   false
+ExperimentalAutoDetectBinPacking: false
+ForEachMacros:   [ foreach, Q_FOREACH, BOOST_FOREACH ]
+IndentCaseLabels: true
+IndentFunctionDeclarationAfterType: false
+IndentWidth:     4
+IndentWrappedFunctionNames: false
+KeepEmptyLinesAtTheStartOfBlocks: false
+Language:        Cpp
+MaxEmptyLinesToKeep: 2
+NamespaceIndentation: None
+ObjCSpaceAfterProperty: false
+ObjCSpaceBeforeProtocolList: false
+PenaltyBreakBeforeFirstCallParameter: 19
+PenaltyBreakComment: 300
+PenaltyBreakFirstLessLess: 120
+PenaltyBreakString: 1000
+PenaltyExcessCharacter: 1000000
+PenaltyReturnTypeOnItsOwnLine: 200
+PointerAlignment: Left
+SpaceAfterCStyleCast: false
+SpaceBeforeAssignmentOperators: true
+SpaceBeforeParens: ControlStatements
+SpaceInEmptyParentheses: false
+SpacesBeforeTrailingComments: 2
+SpacesInAngles:  false
+SpacesInCStyleCastParentheses: false
+SpacesInContainerLiterals: true
+SpacesInParentheses: false
+SpacesInSquareBrackets: false
+Standard:        Cpp11
+TabWidth:        4
+UseTab:          Never