Fixed xerces DOM construction related memory leaks

* Wrapped xerces DOM and support class instances in now DomDocumentGuard scope-guard class
* FunctionReadDirectory class contains interal std::stack instance to store DomDocumentGuard instances
** wrapped in std::shared_ptr as FunctionReadDirectory is internally cloned by xalan...
** this is needed as the DOM has to preserved longer than the external function execution scope
* Sadly XMLCh xerces strings have to be manually released
** added appropriate xercesc::XMLString::release calls
* xalan::XercesDOMWrapperParsedSource does not mirror a given xerces DOM but convert it on instantiation
** this is why there is a dedicated finalize member method in InputXSLT::DomDocumentGuard
* In short: I do not like the amount of trickery needed to simply prevent memory leaks in this context
** there sadly doesn't seem to be a substantially easier way to return arbitrary DOM trees from a external function

2 files changed, 81 insertions, 0 deletions

diff --git a/src/support/dom_document_guard.cc b/src/support/dom_document_guard.cc
new file mode 100644
index 0000000..a83345f
--- /dev/null
+++ b/src/support/dom_document_guard.cc
@@ -0,0 +1,45 @@
+#include "support/dom_document_guard.h"
+
+#include <xercesc/dom/DOMImplementation.hpp>
+#include <xercesc/util/XMLString.hpp>
+
+namespace InputXSLT {
+
+DomDocumentGuard::DomDocumentGuard(const std::string& rootNode):
+	parser_(),
+	dom_support_(parser_),
+	root_node_name_(
+		xercesc::XMLString::transcode(rootNode.data())
+	),
+	document_(
+		xercesc::DOMImplementation::getImplementation()->createDocument(
+			nullptr,
+			root_node_name_,
+			nullptr
+		)
+	),
+	parsed_source_() { }
+
+DomDocumentGuard::~DomDocumentGuard() {
+	xercesc::XMLString::release(&this->root_node_name_);
+
+	this->document_->release();
+}
+
+xercesc::DOMDocument* DomDocumentGuard::operator->() {
+	return this->document_;
+}
+
+xalan::XalanDocument* DomDocumentGuard::finalize() {
+	this->parsed_source_.reset(
+		new xalan::XercesDOMWrapperParsedSource(
+				document_,
+				parser_,
+				dom_support_
+		)
+	);
+
+	return this->parsed_source_->getDocument();
+}
+
+}
diff --git a/src/support/dom_document_guard.h b/src/support/dom_document_guard.h
new file mode 100644
index 0000000..decca01
--- /dev/null
+++ b/src/support/dom_document_guard.h
@@ -0,0 +1,36 @@
+#ifndef INPUTXSLT_SRC_SUPPORT_DOM_DOCUMENT_GUARD_H_
+#define INPUTXSLT_SRC_SUPPORT_DOM_DOCUMENT_GUARD_H_
+
+#include <xalanc/XercesParserLiaison/XercesParserLiaison.hpp>
+#include <xalanc/XercesParserLiaison/XercesDOMSupport.hpp>
+#include <xalanc/XalanTransformer/XercesDOMWrapperParsedSource.hpp>
+
+#include <xercesc/dom/DOMDocument.hpp>
+
+#include <string>
+#include <memory>
+
+#include "common.h"
+
+namespace InputXSLT {
+
+class DomDocumentGuard {
+	public:
+		DomDocumentGuard(const std::string&);
+		~DomDocumentGuard();
+
+		xercesc::DOMDocument* operator->();
+		xalan::XalanDocument* finalize();
+
+	private:
+		xalan::XercesParserLiaison parser_;
+		xalan::XercesDOMSupport dom_support_;
+		XMLCh* root_node_name_;
+		xercesc::DOMDocument* const document_;
+		std::unique_ptr<xalan::XercesDOMWrapperParsedSource> parsed_source_;
+
+};
+
+}
+
+#endif  // INPUTXSLT_SRC_SUPPORT_DOM_DOCUMENT_GUARD_H_