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Daniel Veillard | 28fdf8b | 2011-03-07 08:12:39 +0800 | [diff] [blame] | 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" 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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 |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 11 | incompatible changes. The main goals were:</p><ul> |
| 12 | <li>a general cleanup. A number of mistakes inherited from the very early |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 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 |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 28 | mail</a>:</p><ol> |
| 29 | <li>The package name have changed from libxml to libxml2, the library name |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 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/->root/->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: |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 49 | <ol> |
| 50 | <li>lazy one, use the compatibility call |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 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> |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 60 | </ol> |
| 61 | <p>Note also that with the new default the output functions don't add any |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 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> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 65 | </li> |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 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 |
Daniel Veillard | 480363b | 2001-03-16 22:04:15 +0000 | [diff] [blame] | 69 | <pre>xml2-config --cflags</pre> |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 70 | <p>output to generate you compile commands this will probably work out of |
| 71 | the box</p> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 72 | </li> |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 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 |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 77 | compatibility. They offers the following:</p><ol> |
| 78 | <li>similar include naming, one should use |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 79 | <strong>#include<libxml/...></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 |
Daniel Veillard | e38217a | 2013-05-10 15:40:13 +0800 | [diff] [blame] | 86 | following:</p><ol> |
| 87 | <li>install the libxml-1.8.8 (and libxml-devel-1.8.8) packages</li> |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 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> |
Daniel Veillard | 0b28e88 | 2002-07-24 23:47:05 +0000 | [diff] [blame] | 95 | <li>Recompile, check compatibility, it should still work</li> |
Daniel Veillard | f781dba | 2006-06-09 13:34:49 +0000 | [diff] [blame] | 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> |