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   10 </style><title>Upgrading 1.x code</title></head><body bgcolor="#8b7765" text="#000000" link="#a06060" vlink="#000000"><table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr><td width="120"><a href="http://swpat.ffii.org/"><img src="epatents.png" alt="Action against software patents" /></a></td><td width="180"><a href="http://www.gnome.org/"><img src="gnome2.png" alt="Gnome2 Logo" /></a><a href="http://www.w3.org/Status"><img src="w3c.png" alt="W3C Logo" /></a><a href="http://www.redhat.com/"><img src="redhat.gif" alt="Red Hat Logo" /></a><div align="left"><a href="http://xmlsoft.org/"><img src="Libxml2-Logo-180x168.gif" alt="Made with Libxml2 Logo" /></a></div></td><td><table border="0" width="90%" cellpadding="2" cellspacing="0" align="center" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3" bgcolor="#fffacd"><tr><td align="center"><h1>The XML C parser and toolkit of Gnome</h1><h2>Upgrading 1.x code</h2></td></tr></table></td></tr></table></td></tr></table><table border="0" cellpadding="4" cellspacing="0" width="100%" align="center"><tr><td bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="2" width="100%"><tr><td valign="top" width="200" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Developer Menu</b></center></td></tr><tr><td bgcolor="#fffacd"><form action="search.php" enctype="application/x-www-form-urlencoded" method="get"><input name="query" type="text" size="20" value="" /><input name="submit" type="submit" value="Search ..." /></form><ul><li><a href="index.html" style="font-weight:bold">Main Menu</a></li><li><a href="html/index.html" style="font-weight:bold">Reference Manual</a></li><li><a href="examples/index.html" style="font-weight:bold">Code Examples</a></li><li><a href="guidelines.html">XML Guidelines</a></li><li><a href="tutorial/index.html">Tutorial</a></li><li><a href="xmlreader.html">The Reader Interface</a></li><li><a href="ChangeLog.html">ChangeLog</a></li><li><a href="XSLT.html">XSLT</a></li><li><a href="python.html">Python and bindings</a></li><li><a href="architecture.html">libxml2 architecture</a></li><li><a href="tree.html">The tree output</a></li><li><a href="interface.html">The SAX interface</a></li><li><a href="xmlmem.html">Memory Management</a></li><li><a href="xmlio.html">I/O Interfaces</a></li><li><a href="library.html">The parser interfaces</a></li><li><a href="entities.html">Entities or no entities</a></li><li><a href="namespaces.html">Namespaces</a></li><li><a href="upgrade.html">Upgrading 1.x code</a></li><li><a href="threads.html">Thread safety</a></li><li><a href="DOM.html">DOM Principles</a></li><li><a href="example.html">A real example</a></li><li><a href="xml.html">flat page</a>, <a href="site.xsl">stylesheet</a></li></ul></td></tr></table><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>API Indexes</b></center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="APIchunk0.html">Alphabetic</a></li><li><a href="APIconstructors.html">Constructors</a></li><li><a href="APIfunctions.html">Functions/Types</a></li><li><a href="APIfiles.html">Modules</a></li><li><a href="APIsymbols.html">Symbols</a></li></ul></td></tr></table><table width="100%" border="0" cellspacing="1" cellpadding="3"><tr><td colspan="1" bgcolor="#eecfa1" align="center"><center><b>Related links</b></center></td></tr><tr><td bgcolor="#fffacd"><ul><li><a href="http://mail.gnome.org/archives/xml/">Mail archive</a></li><li><a href="http://xmlsoft.org/XSLT/">XSLT libxslt</a></li><li><a href="http://phd.cs.unibo.it/gdome2/">DOM gdome2</a></li><li><a href="http://www.aleksey.com/xmlsec/">XML-DSig xmlsec</a></li><li><a href="ftp://xmlsoft.org/">FTP</a></li><li><a href="http://www.zlatkovic.com/projects/libxml/">Windows binaries</a></li><li><a href="http://opencsw.org/packages/libxml2">Solaris binaries</a></li><li><a href="http://www.explain.com.au/oss/libxml2xslt.html">MacOsX binaries</a></li><li><a href="http://lxml.de/">lxml Python bindings</a></li><li><a href="http://cpan.uwinnipeg.ca/dist/XML-LibXML">Perl bindings</a></li><li><a href="http://libxmlplusplus.sourceforge.net/">C++ bindings</a></li><li><a href="http://www.zend.com/php5/articles/php5-xmlphp.php#Heading4">PHP bindings</a></li><li><a href="http://sourceforge.net/projects/libxml2-pas/">Pascal bindings</a></li><li><a href="http://libxml.rubyforge.org/">Ruby bindings</a></li><li><a href="http://tclxml.sourceforge.net/">Tcl bindings</a></li><li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml2">Bug Tracker</a></li></ul></td></tr></table></td></tr></table></td><td valign="top" bgcolor="#8b7765"><table border="0" cellspacing="0" cellpadding="1" width="100%"><tr><td><table border="0" cellspacing="0" cellpadding="1" width="100%" bgcolor="#000000"><tr><td><table border="0" cellpadding="3" cellspacing="1" width="100%"><tr><td bgcolor="#fffacd"><p>Incompatible changes:</p><p>Version 2 of libxml2 is the first version introducing serious backward
   11 incompatible changes. The main goals were:</p><ul>
   12   <li>a general cleanup. A number of mistakes inherited from the very early
   13     versions couldn't be changed due to compatibility constraints. Example
   14     the "childs" element in the nodes.</li>
   15   <li>Uniformization of the various nodes, at least for their header and link
   16     parts (doc, parent, children, prev, next), the goal is a simpler
   17     programming model and simplifying the task of the DOM implementors.</li>
   18   <li>better conformances to the XML specification, for example version 1.x
   19     had an heuristic to try to detect ignorable white spaces. As a result the
   20     SAX event generated were ignorableWhitespace() while the spec requires
   21     character() in that case. This also mean that a number of DOM node
   22     containing blank text may populate the DOM tree which were not present
   23     before.</li>
   24 </ul><h3>How to fix libxml-1.x code:</h3><p>So client code of libxml designed to run with version 1.x may have to be
   25 changed to compile against version 2.x of libxml. Here is a list of changes
   26 that I have collected, they may not be sufficient, so in case you find other
   27 change which are required, <a href="mailto:Daniel.Veillard@w3.org">drop me a
   28 mail</a>:</p><ol>
   29   <li>The package name have changed from libxml to libxml2, the library name
   30     is now -lxml2 . There is a new xml2-config script which should be used to
   31     select the right parameters libxml2</li>
   32   <li>Node <strong>childs</strong> field has been renamed
   33     <strong>children</strong> so s/childs/children/g should be  applied
   34     (probability of having "childs" anywhere else is close to 0+</li>
   35   <li>The document don't have anymore a <strong>root</strong> element it has
   36     been replaced by <strong>children</strong> and usually you will get a
   37     list of element here. For example a Dtd element for the internal subset
   38     and it's declaration may be found in that list, as well as processing
   39     instructions or comments found before or after the document root element.
   40     Use <strong>xmlDocGetRootElement(doc)</strong> to get the root element of
   41     a document. Alternatively if you are sure to not reference DTDs nor have
   42     PIs or comments before or after the root element
   43     s/-&gt;root/-&gt;children/g will probably do it.</li>
   44   <li>The white space issue, this one is more complex, unless special case of
   45     validating parsing, the line breaks and spaces usually used for indenting
   46     and formatting the document content becomes significant. So they are
   47     reported by SAX and if your using the DOM tree, corresponding nodes are
   48     generated. Too approach can be taken:
   49     <ol>
   50       <li>lazy one, use the compatibility call
   51         <strong>xmlKeepBlanksDefault(0)</strong> but be aware that you are
   52         relying on a special (and possibly broken) set of heuristics of
   53         libxml to detect ignorable blanks. Don't complain if it breaks or
   54         make your application not 100% clean w.r.t. to it's input.</li>
   55       <li>the Right Way: change you code to accept possibly insignificant
   56         blanks characters, or have your tree populated with weird blank text
   57         nodes. You can spot them using the commodity function
   58         <strong>xmlIsBlankNode(node)</strong> returning 1 for such blank
   59         nodes.</li>
   60     </ol>
   61     <p>Note also that with the new default the output functions don't add any
   62     extra indentation when saving a tree in order to be able to round trip
   63     (read and save) without inflating the document with extra formatting
   64     chars.</p>
   65   </li>
   66   <li>The include path has changed to $prefix/libxml/ and the includes
   67     themselves uses this new prefix in includes instructions... If you are
   68     using (as expected) the
   69     <pre>xml2-config --cflags</pre>
   70     <p>output to generate you compile commands this will probably work out of
   71     the box</p>
   72   </li>
   73   <li>xmlDetectCharEncoding takes an extra argument indicating the length in
   74     byte of the head of the document available for character detection.</li>
   75 </ol><h3>Ensuring both libxml-1.x and libxml-2.x compatibility</h3><p>Two new version of libxml (1.8.11) and libxml2 (2.3.4) have been released
   76 to allow smooth upgrade of existing libxml v1code while retaining
   77 compatibility. They offers the following:</p><ol>
   78   <li>similar include naming, one should use
   79     <strong>#include&lt;libxml/...&gt;</strong> in both cases.</li>
   80   <li>similar identifiers defined via macros for the child and root fields:
   81     respectively <strong>xmlChildrenNode</strong> and
   82     <strong>xmlRootNode</strong></li>
   83   <li>a new macro <strong>LIBXML_TEST_VERSION</strong> which should be
   84     inserted once in the client code</li>
   85 </ol><p>So the roadmap to upgrade your existing libxml applications is the
   86 following:</p><ol>
   87   <li>install the  libxml-1.8.8 (and libxml-devel-1.8.8) packages</li>
   88   <li>find all occurrences where the xmlDoc <strong>root</strong> field is
   89     used and change it to <strong>xmlRootNode</strong></li>
   90   <li>similarly find all occurrences where the xmlNode
   91     <strong>childs</strong> field is used and change it to
   92     <strong>xmlChildrenNode</strong></li>
   93   <li>add a <strong>LIBXML_TEST_VERSION</strong> macro somewhere in your
   94     <strong>main()</strong> or in the library init entry point</li>
   95   <li>Recompile, check compatibility, it should still work</li>
   96   <li>Change your configure script to look first for xml2-config and fall
   97     back using xml-config . Use the --cflags and --libs output of the command
   98     as the Include and Linking parameters needed to use libxml.</li>
   99   <li>install libxml2-2.3.x and  libxml2-devel-2.3.x (libxml-1.8.y and
  100     libxml-devel-1.8.y can be kept simultaneously)</li>
  101   <li>remove your config.cache, relaunch your configuration mechanism, and
  102     recompile, if steps 2 and 3 were done right it should compile as-is</li>
  103   <li>Test that your application is still running correctly, if not this may
  104     be due to extra empty nodes due to formating spaces being kept in libxml2
  105     contrary to libxml1, in that case insert xmlKeepBlanksDefault(1) in your
  106     code before calling the parser (next to
  107     <strong>LIBXML_TEST_VERSION</strong> is a fine place).</li>
  108 </ol><p>Following those steps should work. It worked for some of my own code.</p><p>Let me put some emphasis on the fact that there is far more changes from
  109 libxml 1.x to 2.x than the ones you may have to patch for. The overall code
  110 has been considerably cleaned up and the conformance to the XML specification
  111 has been drastically improved too. Don't take those changes as an excuse to
  112 not upgrade, it may cost a lot on the long term ...</p><p><a href="bugs.html">Daniel Veillard</a></p></td></tr></table></td></tr></table></td></tr></table></td></tr></table></td></tr></table></body></html>