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10: </style><title>FAQ</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>FAQ</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>Main 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">Home</a></li><li><a href="html/index.html">Reference Manual</a></li><li><a href="intro.html">Introduction</a></li><li><a href="FAQ.html">FAQ</a></li><li><a href="docs.html" style="font-weight:bold">Developer Menu</a></li><li><a href="bugs.html">Reporting bugs and getting help</a></li><li><a href="help.html">How to help</a></li><li><a href="downloads.html">Downloads</a></li><li><a href="news.html">Releases</a></li><li><a href="XMLinfo.html">XML</a></li><li><a href="XSLT.html">XSLT</a></li><li><a href="xmldtd.html">Validation & DTDs</a></li><li><a href="encoding.html">Encodings support</a></li><li><a href="catalog.html">Catalog support</a></li><li><a href="namespaces.html">Namespaces</a></li><li><a href="contribs.html">Contributions</a></li><li><a href="examples/index.html" style="font-weight:bold">Code Examples</a></li><li><a href="html/index.html" style="font-weight:bold">API Menu</a></li><li><a href="guidelines.html">XML Guidelines</a></li><li><a href="ChangeLog.html">Recent Changes</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://codespeak.net/lxml/">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>Table of Contents:</p><ul><li><a href="FAQ.html#License">License(s)</a></li>
11: <li><a href="FAQ.html#Installati">Installation</a></li>
12: <li><a href="FAQ.html#Compilatio">Compilation</a></li>
13: <li><a href="FAQ.html#Developer">Developer corner</a></li>
14: </ul><h3><a name="License" id="License">License</a>(s)</h3><ol><li><em>Licensing Terms for libxml</em>
15: <p>libxml2 is released under the <a href="http://www.opensource.org/licenses/mit-license.html">MIT
16: License</a>; see the file Copyright in the distribution for the precise
17: wording</p>
18: </li>
19: <li><em>Can I embed libxml2 in a proprietary application ?</em>
20: <p>Yes. The MIT License allows you to keep proprietary the changes you
21: made to libxml, but it would be graceful to send-back bug fixes and
22: improvements as patches for possible incorporation in the main
23: development tree.</p>
24: </li>
25: </ol><h3><a name="Installati" id="Installati">Installation</a></h3><ol><li><strong><span style="background-color: #FF0000">Do Not Use
26: libxml1</span></strong>, use libxml2</li>
27: <p></p>
28: <li><em>Where can I get libxml</em> ?
29: <p>The original distribution comes from <a href="ftp://xmlsoft.org/libxml2/">xmlsoft.org</a> or <a href="ftp://ftp.gnome.org/pub/GNOME/sources/libxml2/2.6/">gnome.org</a></p>
30: <p>Most Linux and BSD distributions include libxml, this is probably the
31: safer way for end-users to use libxml.</p>
32: <p>David Doolin provides precompiled Windows versions at <a href="http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/ ">http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/</a></p>
33: </li>
34: <p></p>
35: <li><em>I see libxml and libxml2 releases, which one should I install ?</em>
36: <ul><li>If you are not constrained by backward compatibility issues with
37: existing applications, install libxml2 only</li>
38: <li>If you are not doing development, you can safely install both.
39: Usually the packages <a href="http://rpmfind.net/linux/RPM/libxml.html">libxml</a> and <a href="http://rpmfind.net/linux/RPM/libxml2.html">libxml2</a> are
40: compatible (this is not the case for development packages).</li>
41: <li>If you are a developer and your system provides separate packaging
42: for shared libraries and the development components, it is possible
43: to install libxml and libxml2, and also <a href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a>
44: and <a href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml2-devel</a>
45: too for libxml2 >= 2.3.0</li>
46: <li>If you are developing a new application, please develop against
47: libxml2(-devel)</li>
48: </ul></li>
49: <li><em>I can't install the libxml package, it conflicts with libxml0</em>
50: <p>You probably have an old libxml0 package used to provide the shared
51: library for libxml.so.0, you can probably safely remove it. The libxml
52: packages provided on <a href="ftp://xmlsoft.org/libxml2/">xmlsoft.org</a> provide
53: libxml.so.0</p>
54: </li>
55: <li><em>I can't install the libxml(2) RPM package due to failed
56: dependencies</em>
57: <p>The most generic solution is to re-fetch the latest src.rpm , and
58: rebuild it locally with</p>
59: <p><code>rpm --rebuild libxml(2)-xxx.src.rpm</code>.</p>
60: <p>If everything goes well it will generate two binary rpm packages (one
61: providing the shared libs and xmllint, and the other one, the -devel
62: package, providing includes, static libraries and scripts needed to build
63: applications with libxml(2)) that you can install locally.</p>
64: </li>
65: </ol><h3><a name="Compilatio" id="Compilatio">Compilation</a></h3><ol><li><em>What is the process to compile libxml2 ?</em>
66: <p>As most UNIX libraries libxml2 follows the "standard":</p>
67: <p><code>gunzip -c xxx.tar.gz | tar xvf -</code></p>
68: <p><code>cd libxml-xxxx</code></p>
69: <p><code>./configure --help</code></p>
70: <p>to see the options, then the compilation/installation proper</p>
71: <p><code>./configure [possible options]</code></p>
72: <p><code>make</code></p>
73: <p><code>make install</code></p>
74: <p>At that point you may have to rerun ldconfig or a similar utility to
75: update your list of installed shared libs.</p>
76: </li>
77: <li><em>What other libraries are needed to compile/install libxml2 ?</em>
78: <p>Libxml2 does not require any other library, the normal C ANSI API
79: should be sufficient (please report any violation to this rule you may
80: find).</p>
81: <p>However if found at configuration time libxml2 will detect and use the
82: following libs:</p>
83: <ul><li><a href="http://www.info-zip.org/pub/infozip/zlib/">libz</a> : a
84: highly portable and available widely compression library.</li>
85: <li>iconv: a powerful character encoding conversion library. It is
86: included by default in recent glibc libraries, so it doesn't need to
87: be installed specifically on Linux. It now seems a <a href="http://www.opennc.org/onlinepubs/7908799/xsh/iconv.html">part
88: of the official UNIX</a> specification. Here is one <a href="http://www.gnu.org/software/libiconv/">implementation of the
89: library</a> which source can be found <a href="ftp://ftp.ilog.fr/pub/Users/haible/gnu/">here</a>.</li>
90: </ul></li>
91: <p></p>
92: <li><em>Make check fails on some platforms</em>
93: <p>Sometimes the regression tests' results don't completely match the
94: value produced by the parser, and the makefile uses diff to print the
95: delta. On some platforms the diff return breaks the compilation process;
96: if the diff is small this is probably not a serious problem.</p>
97: <p>Sometimes (especially on Solaris) make checks fail due to limitations
98: in make. Try using GNU-make instead.</p>
99: </li>
100: <li><em>I use the SVN version and there is no configure script</em>
101: <p>The configure script (and other Makefiles) are generated. Use the
102: autogen.sh script to regenerate the configure script and Makefiles,
103: like:</p>
104: <p><code>./autogen.sh --prefix=/usr --disable-shared</code></p>
105: </li>
106: <li><em>I have troubles when running make tests with gcc-3.0</em>
107: <p>It seems the initial release of gcc-3.0 has a problem with the
108: optimizer which miscompiles the URI module. Please use another
109: compiler.</p>
110: </li>
111: </ol><h3><a name="Developer" id="Developer">Developer</a> corner</h3><ol><li><em>Troubles compiling or linking programs using libxml2</em>
112: <p>Usually the problem comes from the fact that the compiler doesn't get
113: the right compilation or linking flags. There is a small shell script
114: <code>xml2-config</code> which is installed as part of libxml2 usual
115: install process which provides those flags. Use</p>
116: <p><code>xml2-config --cflags</code></p>
117: <p>to get the compilation flags and</p>
118: <p><code>xml2-config --libs</code></p>
119: <p>to get the linker flags. Usually this is done directly from the
120: Makefile as:</p>
121: <p><code>CFLAGS=`xml2-config --cflags`</code></p>
122: <p><code>LIBS=`xml2-config --libs`</code></p>
123: </li>
124: <li><em>I want to install my own copy of libxml2 in my home directory and
125: link my programs against it, but it doesn't work</em>
126: <p>There are many different ways to accomplish this. Here is one way to
127: do this under Linux. Suppose your home directory is <code>/home/user.
128: </code>Then:</p>
129: <ul><li>Create a subdirectory, let's call it <code>myxml</code></li>
130: <li>unpack the libxml2 distribution into that subdirectory</li>
131: <li>chdir into the unpacked distribution
132: (<code>/home/user/myxml/libxml2 </code>)</li>
133: <li>configure the library using the "<code>--prefix</code>" switch,
134: specifying an installation subdirectory in
135: <code>/home/user/myxml</code>, e.g.
136: <p><code>./configure --prefix /home/user/myxml/xmlinst</code> {other
137: configuration options}</p>
138: </li>
139: <li>now run <code>make</code> followed by <code>make install</code></li>
140: <li>At this point, the installation subdirectory contains the complete
141: "private" include files, library files and binary program files (e.g.
142: xmllint), located in
143: <p><code>/home/user/myxml/xmlinst/lib,
144: /home/user/myxml/xmlinst/include </code> and <code>
145: /home/user/myxml/xmlinst/bin</code></p>
146: respectively.</li>
147: <li>In order to use this "private" library, you should first add it to
148: the beginning of your default PATH (so that your own private program
149: files such as xmllint will be used instead of the normal system
150: ones). To do this, the Bash command would be
151: <p><code>export PATH=/home/user/myxml/xmlinst/bin:$PATH</code></p>
152: </li>
153: <li>Now suppose you have a program <code>test1.c</code> that you would
154: like to compile with your "private" library. Simply compile it using
155: the command
156: <p><code>gcc `xml2-config --cflags --libs` -o test test.c</code></p>
157: Note that, because your PATH has been set with <code>
158: /home/user/myxml/xmlinst/bin</code> at the beginning, the xml2-config
159: program which you just installed will be used instead of the system
160: default one, and this will <em>automatically</em> get the correct
161: libraries linked with your program.</li>
162: </ul></li>
163:
164: <p></p>
165: <li><em>xmlDocDump() generates output on one line.</em>
166: <p>Libxml2 will not <strong>invent</strong> spaces in the content of a
167: document since <strong>all spaces in the content of a document are
168: significant</strong>. If you build a tree from the API and want
169: indentation:</p>
170: <ol><li>the correct way is to generate those yourself too.</li>
171: <li>the dangerous way is to ask libxml2 to add those blanks to your
172: content <strong>modifying the content of your document in the
173: process</strong>. The result may not be what you expect. There is
174: <strong>NO</strong> way to guarantee that such a modification won't
175: affect other parts of the content of your document. See <a href="http://xmlsoft.org/html/libxml-parser.html#xmlKeepBlanksDefault">xmlKeepBlanksDefault
176: ()</a> and <a href="http://xmlsoft.org/html/libxml-tree.html#xmlSaveFormatFile">xmlSaveFormatFile
177: ()</a></li>
178: </ol></li>
179: <p></p>
180: <li><em>Extra nodes in the document:</em>
181: <p><em>For an XML file as below:</em></p>
182: <pre><?xml version="1.0"?>
183: <PLAN xmlns="http://www.argus.ca/autotest/1.0/">
184: <NODE CommFlag="0"/>
185: <NODE CommFlag="1"/>
186: </PLAN></pre>
187: <p><em>after parsing it with the function
188: pxmlDoc=xmlParseFile(...);</em></p>
189: <p><em>I want to the get the content of the first node (node with the
190: CommFlag="0")</em></p>
191: <p><em>so I did it as following;</em></p>
192: <pre>xmlNodePtr pnode;
193: pnode=pxmlDoc->children->children;</pre>
194: <p><em>but it does not work. If I change it to</em></p>
195: <pre>pnode=pxmlDoc->children->children->next;</pre>
196: <p><em>then it works. Can someone explain it to me.</em></p>
197: <p></p>
198: <p>In XML all characters in the content of the document are significant
199: <strong>including blanks and formatting line breaks</strong>.</p>
200: <p>The extra nodes you are wondering about are just that, text nodes with
201: the formatting spaces which are part of the document but that people tend
202: to forget. There is a function <a href="http://xmlsoft.org/html/libxml-parser.html">xmlKeepBlanksDefault
203: ()</a> to remove those at parse time, but that's an heuristic, and its
204: use should be limited to cases where you are certain there is no
205: mixed-content in the document.</p>
206: </li>
207: <li><em>I get compilation errors of existing code like when accessing
208: <strong>root</strong> or <strong>child fields</strong> of nodes.</em>
209: <p>You are compiling code developed for libxml version 1 and using a
210: libxml2 development environment. Either switch back to libxml v1 devel or
211: even better fix the code to compile with libxml2 (or both) by <a href="upgrade.html">following the instructions</a>.</p>
212: </li>
213: <li><em>I get compilation errors about non existing
214: <strong>xmlRootNode</strong> or <strong>xmlChildrenNode</strong>
215: fields.</em>
216: <p>The source code you are using has been <a href="upgrade.html">upgraded</a> to be able to compile with both libxml
217: and libxml2, but you need to install a more recent version:
218: libxml(-devel) >= 1.8.8 or libxml2(-devel) >= 2.1.0</p>
219: </li>
220: <li><em>Random crashes in threaded applications</em>
221: <p>Read and follow all advices on the <a href="threads.html">thread
222: safety</a> page, and make 100% sure you never call xmlCleanupParser()
223: while the library or an XML document might still be in use by another
224: thread.</p>
225: </li>
226: <li><em>The example provided in the web page does not compile.</em>
227: <p>It's hard to maintain the documentation in sync with the code
228: <grin/> ...</p>
229: <p>Check the previous points 1/ and 2/ raised before, and please send
230: patches.</p>
231: </li>
232: <li><em>Where can I get more examples and information than provided on the
233: web page?</em>
234: <p>Ideally a libxml2 book would be nice. I have no such plan ... But you
235: can:</p>
236: <ul><li>check more deeply the <a href="html/libxml-lib.html">existing
237: generated doc</a></li>
238: <li>have a look at <a href="examples/index.html">the set of
239: examples</a>.</li>
240: <li>look for examples of use for libxml2 function using the Gnome code
241: or by asking on Google.</li>
242: <li><a href="http://svn.gnome.org/viewvc/libxml2/trunk/">Browse
243: the libxml2 source</a> , I try to write code as clean and documented
244: as possible, so looking at it may be helpful. In particular the code
245: of <a href="http://svn.gnome.org/viewvc/libxml2/trunk/xmllint.c?view=markup">xmllint.c</a> and of the various testXXX.c test programs should
246: provide good examples of how to do things with the library.</li>
247: </ul></li>
248: <p></p>
249: <li><em>What about C++ ?</em>
250: <p>libxml2 is written in pure C in order to allow easy reuse on a number
251: of platforms, including embedded systems. I don't intend to convert to
252: C++.</p>
253: <p>There is however a C++ wrapper which may fulfill your needs:</p>
254: <ul><li>by Ari Johnson <ari@btigate.com>:
255: <p>Website: <a href="http://libxmlplusplus.sourceforge.net/">http://libxmlplusplus.sourceforge.net/</a></p>
256: <p>Download: <a href="http://sourceforge.net/project/showfiles.php?group_id=12999">http://sourceforge.net/project/showfiles.php?group_id=12999</a></p>
257: </li>
258: </ul></li>
259: <li><em>How to validate a document a posteriori ?</em>
260: <p>It is possible to validate documents which had not been validated at
261: initial parsing time or documents which have been built from scratch
262: using the API. Use the <a href="http://xmlsoft.org/html/libxml-valid.html#xmlValidateDtd">xmlValidateDtd()</a>
263: function. It is also possible to simply add a DTD to an existing
264: document:</p>
265: <pre>xmlDocPtr doc; /* your existing document */
266: xmlDtdPtr dtd = xmlParseDTD(NULL, filename_of_dtd); /* parse the DTD */
267:
268: dtd->name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */
269:
270: doc->intSubset = dtd;
271: if (doc->children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd);
272: else xmlAddPrevSibling(doc->children, (xmlNodePtr)dtd);
273: </pre>
274: </li>
275: <li><em>So what is this funky "xmlChar" used all the time?</em>
276: <p>It is a null terminated sequence of utf-8 characters. And only utf-8!
277: You need to convert strings encoded in different ways to utf-8 before
278: passing them to the API. This can be accomplished with the iconv library
279: for instance.</p>
280: </li>
281: <li>etc ...</li>
282: </ol><p></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>
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