FAQ.html revision 8a469171206edc0dbb25d115b7454c6e599ab1c5
1<?xml version="1.0" encoding="ISO-8859-1"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /><link rel="SHORTCUT ICON" href="/favicon.ico" /><style type="text/css"> 4TD {font-family: Verdana,Arial,Helvetica} 5BODY {font-family: Verdana,Arial,Helvetica; margin-top: 2em; margin-left: 0em; margin-right: 0em} 6H1 {font-family: Verdana,Arial,Helvetica} 7H2 {font-family: Verdana,Arial,Helvetica} 8H3 {font-family: Verdana,Arial,Helvetica} 9A:link, A:visited, A:active { text-decoration: underline } 10</style><title>FAQ</title></head><body bgcolor="#8b7765" text="#000000" link="#000000" vlink="#000000"><table border="0" width="100%" cellpadding="5" cellspacing="0" align="center"><tr><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 for 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="intro.html">Introduction</a></li><li><a href="FAQ.html">FAQ</a></li><li><a href="docs.html">Developer Documentation</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">News</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="guidelines.html">XML Guidelines</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://garypennington.net/libxml2/">Solaris binaries</a></li><li><a href="http://www.zveno.com/open_source/libxml2xslt.html">MacOsX binaries</a></li><li><a href="http://sourceforge.net/projects/libxml2-pas/">Pascal bindings</a></li><li><a href="http://bugzilla.gnome.org/buglist.cgi?product=libxml&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 26 Not Use libxml1</span></strong>, use libxml2</li> 27 <li><em>Where can I get libxml</em> ? 28 <p>The original distribution comes from <a href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> or <a href="ftp://ftp.gnome.org/pub/GNOME/sources/libxml2/2.5/">gnome.org</a></p> 29 <p>Most Linux and BSD distributions include libxml, this is probably the 30 safer way for end-users to use libxml.</p> 31 <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> 32 </li> 33 <li><em>I see libxml and libxml2 releases, which one should I install ?</em> 34 <ul><li>If you are not constrained by backward compatibility issues with 35 existing applications, install libxml2 only</li> 36 <li>If you are not doing development, you can safely install both. 37 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 38 compatible (this is not the case for development packages).</li> 39 <li>If you are a developer and your system provides separate packaging 40 for shared libraries and the development components, it is possible 41 to install libxml and libxml2, and also <a href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a> 42 and <a href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml2-devel</a> 43 too for libxml2 >= 2.3.0</li> 44 <li>If you are developing a new application, please develop against 45 libxml2(-devel)</li> 46 </ul></li> 47 <li><em>I can't install the libxml package, it conflicts with libxml0</em> 48 <p>You probably have an old libxml0 package used to provide the shared 49 library for libxml.so.0, you can probably safely remove it. The libxml 50 packages provided on <a href="ftp://rpmfind.net/pub/libxml/">rpmfind.net</a> provide 51 libxml.so.0</p> 52 </li> 53 <li><em>I can't install the libxml(2) RPM package due to failed 54 dependencies</em> 55 <p>The most generic solution is to re-fetch the latest src.rpm , and 56 rebuild it locally with</p> 57 <p><code>rpm --rebuild libxml(2)-xxx.src.rpm</code>.</p> 58 <p>If everything goes well it will generate two binary rpm packages (one 59 providing the shared libs and xmllint, and the other one, the -devel 60 package, providing includes, static libraries and scripts needed to build 61 applications with libxml(2)) that you can install locally.</p> 62 </li> 63</ol><h3><a name="Compilatio" id="Compilatio">Compilation</a></h3><ol><li><em>What is the process to compile libxml2 ?</em> 64 <p>As most UNIX libraries libxml2 follows the "standard":</p> 65 <p><code>gunzip -c xxx.tar.gz | tar xvf -</code></p> 66 <p><code>cd libxml-xxxx</code></p> 67 <p><code>/configure --help</code></p> 68 <p>to see the options, then the compilation/installation proper</p> 69 <p><code>/configure [possible options]</code></p> 70 <p><code>make</code></p> 71 <p><code>make install</code></p> 72 <p>At that point you may have to rerun ldconfig or a similar utility to 73 update your list of installed shared libs.</p> 74 </li> 75 <li><em>What other libraries are needed to compile/install libxml2 ?</em> 76 <p>Libxml2 does not require any other library, the normal C ANSI API 77 should be sufficient (please report any violation to this rule you may 78 find).</p> 79 <p>However if found at configuration time libxml2 will detect and use the 80 following libs:</p> 81 <ul><li><a href="http://www.info-zip.org/pub/infozip/zlib/">libz</a> : a 82 highly portable and available widely compression library.</li> 83 <li>iconv: a powerful character encoding conversion library. It is 84 included by default in recent glibc libraries, so it doesn't need to 85 be installed specifically on Linux. It now seems a <a href="http://www.opennc.org/onlinepubs/7908799/xsh/iconv.html">part 86 of the official UNIX</a> specification. Here is one <a href="http://www.gnu.org/software/libiconv/">implementation of the 87 library</a> which source can be found <a href="ftp://ftp.ilog.fr/pub/Users/haible/gnu/">here</a>.</li> 88 </ul></li> 89 <li><em>Make check fails on some platforms</em> 90 <p>Sometimes the regression tests' results don't completely match the 91 value produced by the parser, and the makefile uses diff to print the 92 delta. On some platforms the diff return breaks the compilation process; 93 if the diff is small this is probably not a serious problem.</p> 94 <p>Sometimes (especially on Solaris) make checks fail due to limitations 95 in make. Try using GNU-make instead.</p> 96 </li> 97 <li><em>I use the CVS version and there is no configure script</em> 98 <p>The configure script (and other Makefiles) are generated. Use the 99 autogen.sh script to regenerate the configure script and Makefiles, 100 like:</p> 101 <p><code>/autogen.sh --prefix=/usr --disable-shared</code></p> 102 </li> 103 <li><em>I have troubles when running make tests with gcc-3.0</em> 104 <p>It seems the initial release of gcc-3.0 has a problem with the 105 optimizer which miscompiles the URI module. Please use another 106 compiler.</p> 107 </li> 108</ol><h3><a name="Developer" id="Developer">Developer</a> corner</h3><ol><li><em>Troubles compiling or linking programs using libxml2</em> 109 <p>Usually the problem comes from the fact that the compiler doesn't get 110 the right compilation or linking flags. There is a small shell script 111 <code>xml2-config</code> which is installed as part of libxml2 usual 112 install process which provides those flags. Use </p> 113 <p><code>xml2-config --cflags</code></p> 114 <p>to get the compilation flags and</p> 115 <p><code>xml2-config --libs</code></p> 116 <p>to get the linker flags. Usually this is done directly from the 117 Makefile as:</p> 118 <p><code>CFLAGS=`xml2-config --cflags`</code></p> 119 <p><code>LIBS=`xml2-config --libs`</code></p> 120 </li> 121 <li><em>xmlDocDump() generates output on one line.</em> 122 <p>Libxml2 will not <strong>invent</strong> spaces in the content of a 123 document since <strong>all spaces in the content of a document are 124 significant</strong>. If you build a tree from the API and want 125 indentation:</p> 126 <ol><li>the correct way is to generate those yourself too.</li> 127 <li>the dangerous way is to ask libxml2 to add those blanks to your 128 content <strong>modifying the content of your document in the 129 process</strong>. The result may not be what you expect. There is 130 <strong>NO</strong> way to guarantee that such a modification won't 131 affect other parts of the content of your document. See <a href="http://xmlsoft.org/html/libxml-parser.html#XMLKEEPBLANKSDEFAULT">xmlKeepBlanksDefault 132 ()</a> and <a href="http://xmlsoft.org/html/libxml-tree.html#XMLSAVEFORMATFILE">xmlSaveFormatFile 133 ()</a></li> 134 </ol></li> 135 <li>Extra nodes in the document: 136 <p><em>For a XML file as below:</em></p> 137 <pre><?xml version="1.0"?> 138<PLAN xmlns="http://www.argus.ca/autotest/1.0/">; 139<NODE CommFlag="0"/> 140<NODE CommFlag="1"/> 141</PLAN></pre> 142 <p><em>after parsing it with the function 143 pxmlDoc=xmlParseFile(...);</em></p> 144 <p><em>I want to the get the content of the first node (node with the 145 CommFlag="0")</em></p> 146 <p><em>so I did it as following;</em></p> 147 <pre>xmlNodePtr pnode; 148pnode=pxmlDoc->children->children;</pre> 149 <p><em>but it does not work. If I change it to</em></p> 150 <pre>pnode=pxmlDoc->children->children->next;</pre> 151 <p><em>then it works. Can someone explain it to me.</em></p> 152 <p></p> 153 <p>In XML all characters in the content of the document are significant 154 <strong>including blanks and formatting line breaks</strong>.</p> 155 <p>The extra nodes you are wondering about are just that, text nodes with 156 the formatting spaces which are part of the document but that people tend 157 to forget. There is a function <a href="http://xmlsoft.org/html/libxml-parser.html">xmlKeepBlanksDefault 158 ()</a> to remove those at parse time, but that's an heuristic, and its 159 use should be limited to cases where you are certain there is no 160 mixed-content in the document.</p> 161 </li> 162 <li><em>I get compilation errors of existing code like when accessing 163 <strong>root</strong> or <strong>child fields</strong> of nodes.</em> 164 <p>You are compiling code developed for libxml version 1 and using a 165 libxml2 development environment. Either switch back to libxml v1 devel or 166 even better fix the code to compile with libxml2 (or both) by <a href="upgrade.html">following the instructions</a>.</p> 167 </li> 168 <li><em>I get compilation errors about non existing 169 <strong>xmlRootNode</strong> or <strong>xmlChildrenNode</strong> 170 fields.</em> 171 <p>The source code you are using has been <a href="upgrade.html">upgraded</a> to be able to compile with both libxml 172 and libxml2, but you need to install a more recent version: 173 libxml(-devel) >= 1.8.8 or libxml2(-devel) >= 2.1.0</p> 174 </li> 175 <li><em>XPath implementation looks seriously broken</em> 176 <p>XPath implementation prior to 2.3.0 was really incomplete. Upgrade to 177 a recent version, there are no known bugs in the current version.</p> 178 </li> 179 <li><em>The example provided in the web page does not compile.</em> 180 <p>It's hard to maintain the documentation in sync with the code 181 <grin/> ...</p> 182 <p>Check the previous points 1/ and 2/ raised before, and please send 183 patches.</p> 184 </li> 185 <li><em>Where can I get more examples and information than privoded on the 186 web page?</em> 187 <p>Ideally a libxml2 book would be nice. I have no such plan ... But you 188 can:</p> 189 <ul><li>check more deeply the <a href="html/libxml-lib.html">existing 190 generated doc</a></li> 191 <li>look for examples of use for libxml2 function using the Gnome code. 192 For example the following will query the full Gnome CVS base for the 193 use of the <strong>xmlAddChild()</strong> function: 194 <p><a href="http://cvs.gnome.org/lxr/search?string=xmlAddChild">http://cvs.gnome.org/lxr/search?string=xmlAddChild</a></p> 195 <p>This may be slow, a large hardware donation to the gnome project 196 could cure this :-)</p> 197 </li> 198 <li><a href="http://cvs.gnome.org/bonsai/rview.cgi?cvsroot=/cvs/gnome&dir=gnome-xml">Browse 199 the libxml2 source</a> , I try to write code as clean and documented 200 as possible, so looking at it may be helpful. In particular the code 201 of xmllint.c and of the various testXXX.c test programs should 202 provide good examples of how to do things with the library.</li> 203 </ul></li> 204 <li>What about C++ ? 205 <p>libxml2 is written in pure C in order to allow easy reuse on a number 206 of platforms, including embedded systems. I don't intend to convert to 207 C++.</p> 208 <p>There are however a few C++ wrappers which may fulfill your needs:</p> 209 <ul><li>by Ari Johnson <ari@btigate.com>: 210 <p>Website: <a href="http://lusis.org/~ari/xml++/">http://lusis.org/~ari/xml++/</a></p> 211 <p>Download: <a href="http://lusis.org/~ari/xml++/libxml++.tar.gz">http://lusis.org/~ari/xml++/libxml++.tar.gz</a></p> 212 </li> 213 <li>by Peter Jones <pjones@pmade.org> 214 <p>Website: <a href="http://pmade.org/pjones/software/xmlwrapp/">http://pmade.org/pjones/software/xmlwrapp/</a></p> 215 </li> 216 </ul></li> 217 <li>How to validate a document a posteriori ? 218 <p>It is possible to validate documents which had not been validated at 219 initial parsing time or documents which have been built from scratch 220 using the API. Use the <a href="http://xmlsoft.org/html/libxml-valid.html#XMLVALIDATEDTD">xmlValidateDtd()</a> 221 function. It is also possible to simply add a DTD to an existing 222 document:</p> 223 <pre>xmlDocPtr doc; /* your existing document */ 224xmlDtdPtr dtd = xmlParseDTD(NULL, filename_of_dtd); /* parse the DTD */ 225 226 dtd->name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */ 227 228 doc->intSubset = dtd; 229 if (doc->children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd); 230 else xmlAddPrevSibling(doc->children, (xmlNodePtr)dtd); 231 </pre> 232 </li> 233 <li>So what is this funky "xmlChar" used all the time? 234 <p>It is a null terminated sequence of utf-8 characters. And only utf-8! 235 You need to convert strings encoded in different ways to utf-8 before 236 passing them to the API. This can be accomplished with the iconv library 237 for instance.</p> 238 </li> 239 <li>etc ...</li> 240</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> 241
