valgrind: leak on fdo72541-1.fodt

 by 0x43CEBF6E: cppu::OWeakObject::operator new(unsigned long) (weak.hxx:85)
 by 0x449AD12D: SwXMLImport::CreateBodyContentContext(rtl::OUString const&) (xmltext.cxx:77)
 by 0x449790B1: SwXMLBodyContext_Impl::CreateChildContext(unsigned short, rtl::OUString const&, com::sun::star::uno::Reference<com::sun::star::xml::sax::XAttributeList> const&) (xmlimp.cxx:165)
 by 0x1451756D: SvXMLImport::startElement(rtl::OUString const&, com::sun::star::uno::Reference<com::sun::star::xml::sax::XAttributeList> const&) (xmlimp.cxx:684)
 by 0x14511961: SvXMLImportContext::startUnknownElement(rtl::OUString const&, rtl::OUString const&, com::sun::star::uno::Reference<com::sun::star::xml::sax::XFastAttributeList> const&) (xmlictxt.cxx:124)
 by 0x14511306: SvXMLImportContext::startFastElement(int, com::sun::star::uno::Reference<com::sun::star::xml::sax::XFastAttributeList> const&) (xmlictxt.cxx:74)
 by 0x145183A0: SvXMLImport::startFastElement(int, com::sun::star::uno::Reference<com::sun::star::xml::sax::XFastAttributeList> const&) (xmlimp.cxx:834)
 by 0x463D934A: (anonymous namespace)::Entity::startElement((anonymous namespace)::Event*) (fastparser.cxx:456)
 by 0x463DD799: sax_fastparser::FastSaxParserImpl::callbackStartElement(unsigned char const*, unsigned char const*, unsigned char const*, int, unsigned char const**, int, unsigned char const**) (fastparser.cxx:1205)

Change-Id: I667eb9c7205f7e959b8b925d057b686ff74ef4b7
Reviewed-on: https://gerrit.libreoffice.org/42358Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>

xmloff/source/core/xmlimp.cxx

@@ -435,16 +435,32 @@ sal_Int64 SAL_CALL SvXMLImport::getSomething( const uno::Sequence< sal_Int8 >& r
     return 0;
 }
 
+namespace
+{
+    class setFastDocumentHandlerGuard
+    {
+    private:
+        css::uno::Reference<css::xml::sax::XFastParser> mxParser;
+    public:
+        setFastDocumentHandlerGuard(const css::uno::Reference<css::xml::sax::XFastParser>& Parser,
+                                    const css::uno::Reference<css::xml::sax::XFastDocumentHandler>& Handler)
+            : mxParser(Parser)
+        {
+            mxParser->setFastDocumentHandler(Handler);
+        }
+        //guarantee restoration of null document handler
+        ~setFastDocumentHandlerGuard()
+        {
+            mxParser->setFastDocumentHandler(nullptr);
+        }
+    };
+}
+
 // XFastParser
 void SAL_CALL SvXMLImport::parseStream( const xml::sax::InputSource& aInputSource )
 {
-    if ( mxFastDocumentHandler.is() )
-        mxParser->setFastDocumentHandler( mxFastDocumentHandler );
-    else
-        mxParser->setFastDocumentHandler( this );
-
-    mxParser->parseStream( aInputSource );
-    mxParser->setFastDocumentHandler( nullptr );
+    setFastDocumentHandlerGuard aDocumentHandlerGuard(mxParser, mxFastDocumentHandler.is() ? mxFastDocumentHandler : this);
+    mxParser->parseStream(aInputSource);
 }
 
 void SAL_CALL SvXMLImport::setFastDocumentHandler( const uno::Reference< xml::sax::XFastDocumentHandler >& Handler )