Fix -Wweak-vtables warnings in exception classes.

src/exceptions.cpp

@@ -0,0 +1,19 @@
+#include "yaml-cpp/exceptions.h"
+
+namespace YAML {
+
+// These destructors are defined out-of-line so the vtable is only emitted once.
+Exception::~Exception() noexcept {}
+ParserException::~ParserException() noexcept {}
+RepresentationException::~RepresentationException() noexcept {}
+InvalidScalar::~InvalidScalar() noexcept {}
+KeyNotFound::~KeyNotFound() noexcept {}
+InvalidNode::~InvalidNode() noexcept {}
+BadConversion::~BadConversion() noexcept {}
+BadDereference::~BadDereference() noexcept {}
+BadSubscript::~BadSubscript() noexcept {}
+BadPushback::~BadPushback() noexcept {}
+BadInsert::~BadInsert() noexcept {}
+EmitterException::~EmitterException() noexcept {}
+BadFile::~BadFile() noexcept {}
+}