STYLE: Pefer = default to explicitly trivial implementations

This check replaces default bodies of special member functions with
= default;. The explicitly defaulted function declarations enable more
opportunities in optimization, because the compiler might treat
explicitly defaulted functions as trivial.

Additionally, the C++11 use of = default more clearly expreses the
intent for the special member functions.

SRCDIR=/Users/johnsonhj/src/jsoncpp/ #My local SRC
BLDDIR=/Users/johnsonhj/src/jsoncpp/cmake-build-debug/ #My local BLD

cd /Users/johnsonhj/src/jsoncpp/cmake-build-debug/
run-clang-tidy.py -extra-arg=-D__clang__ -checks=-*,modernize-use-equals-default  -header-filter=.* -fix

src/lib_json/json_reader.cpp

@@ -60,7 +60,7 @@ typedef std::auto_ptr<CharReader> CharReaderPtr;
 // ////////////////////////////////
 
 Features::Features()
-     {}
+     = default;
 
 Features Features::all() { return {}; }
 
@@ -1907,7 +1907,7 @@ public:
 };
 
 CharReaderBuilder::CharReaderBuilder() { setDefaults(&settings_); }
-CharReaderBuilder::~CharReaderBuilder() {}
+CharReaderBuilder::~CharReaderBuilder() = default;
 CharReader* CharReaderBuilder::newCharReader() const {
   bool collectComments = settings_["collectComments"].asBool();
   OurFeatures features = OurFeatures::all();

src/lib_json/json_value.cpp

@@ -233,7 +233,7 @@ JSONCPP_NORETURN void throwLogicError(JSONCPP_STRING const& msg) {
 // //////////////////////////////////////////////////////////////////
 // //////////////////////////////////////////////////////////////////
 
-Value::CommentInfo::CommentInfo()  {}
+Value::CommentInfo::CommentInfo()  = default;
 
 Value::CommentInfo::~CommentInfo() {
   if (comment_)

src/lib_json/json_valueiterator.inl

@@ -123,7 +123,7 @@ char const* ValueIteratorBase::memberName(char const** end) const {
 // //////////////////////////////////////////////////////////////////
 // //////////////////////////////////////////////////////////////////
 
-ValueConstIterator::ValueConstIterator() {}
+ValueConstIterator::ValueConstIterator() = default;
 
 ValueConstIterator::ValueConstIterator(
     const Value::ObjectValues::iterator& current)
@@ -146,7 +146,7 @@ operator=(const ValueIteratorBase& other) {
 // //////////////////////////////////////////////////////////////////
 // //////////////////////////////////////////////////////////////////
 
-ValueIterator::ValueIterator() {}
+ValueIterator::ValueIterator() = default;
 
 ValueIterator::ValueIterator(const Value::ObjectValues::iterator& current)
     : ValueIteratorBase(current) {}
@@ -157,7 +157,7 @@ ValueIterator::ValueIterator(const ValueConstIterator& other)
 }
 
 ValueIterator::ValueIterator(const ValueIterator& other)
-    : ValueIteratorBase(other) {}
+     = default;
 
 ValueIterator& ValueIterator::operator=(const SelfType& other) {
   copy(other);

src/lib_json/json_writer.cpp

@@ -346,14 +346,14 @@ JSONCPP_STRING valueToQuotedString(const char* value) {
 
 // Class Writer
 // //////////////////////////////////////////////////////////////////
-Writer::~Writer() {}
+Writer::~Writer() = default;
 
 // Class FastWriter
 // //////////////////////////////////////////////////////////////////
 
 FastWriter::FastWriter()
     
-      {}
+      = default;
 
 void FastWriter::enableYAMLCompatibility() { yamlCompatibilityEnabled_ = true; }
 
@@ -428,7 +428,7 @@ void FastWriter::writeValue(const Value& value) {
 // //////////////////////////////////////////////////////////////////
 
 StyledWriter::StyledWriter()
-     {}
+     = default;
 
 JSONCPP_STRING StyledWriter::write(const Value& root) {
   document_.clear();
@@ -1156,10 +1156,10 @@ bool BuiltStyledStreamWriter::hasCommentForValue(const Value& value) {
 // StreamWriter
 
 StreamWriter::StreamWriter() : sout_(nullptr) {}
-StreamWriter::~StreamWriter() {}
-StreamWriter::Factory::~Factory() {}
+StreamWriter::~StreamWriter() = default;
+StreamWriter::Factory::~Factory() = default;
 StreamWriterBuilder::StreamWriterBuilder() { setDefaults(&settings_); }
-StreamWriterBuilder::~StreamWriterBuilder() {}
+StreamWriterBuilder::~StreamWriterBuilder() = default;
 StreamWriter* StreamWriterBuilder::newStreamWriter() const {
   JSONCPP_STRING indentation = settings_["indentation"].asString();
   JSONCPP_STRING cs_str = settings_["commentStyle"].asString();