1<?xml version="1.0" encoding="UTF-8"?> 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=UTF-8" /><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="#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%" 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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> 11 <li><a href="FAQ.html#License">License(s)</a></li> 12 <li><a href="FAQ.html#Installati">Installation</a></li> 13 <li><a href="FAQ.html#Compilatio">Compilation</a></li> 14 <li><a href="FAQ.html#Developer">Developer corner</a></li> 15</ul><h3><a name="License" id="License">License</a>(s)</h3><ol> 16 <li><em>Licensing Terms for libxml</em> 17 <p>libxml2 is released under the <a href="http://www.opensource.org/licenses/mit-license.html">MIT 18 License</a>; see the file Copyright in the distribution for the precise 19 wording</p> 20 </li> 21 <li><em>Can I embed libxml2 in a proprietary application ?</em> 22 <p>Yes. The MIT License allows you to keep proprietary the changes you 23 made to libxml, but it would be graceful to send-back bug fixes and 24 improvements as patches for possible incorporation in the main 25 development tree.</p> 26 </li> 27</ol><h3><a name="Installati" id="Installati">Installation</a></h3><ol> 28 <li><strong><span style="background-color: #FF0000">Do Not Use 29 libxml1</span></strong>, use libxml2<p></p></li> 30 <li><em>Where can I get libxml</em> ? 31 <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> 32 <p>Most Linux and BSD distributions include libxml, this is probably the 33 safer way for end-users to use libxml.</p> 34 <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> 35 </li> 36 <li><em>I see libxml and libxml2 releases, which one should I install ?</em> 37 <ul> 38 <li>If you are not constrained by backward compatibility issues with 39 existing applications, install libxml2 only</li> 40 <li>If you are not doing development, you can safely install both. 41 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 42 compatible (this is not the case for development packages).</li> 43 <li>If you are a developer and your system provides separate packaging 44 for shared libraries and the development components, it is possible 45 to install libxml and libxml2, and also <a href="http://rpmfind.net/linux/RPM/libxml-devel.html">libxml-devel</a> 46 and <a href="http://rpmfind.net/linux/RPM/libxml2-devel.html">libxml2-devel</a> 47 too for libxml2 >= 2.3.0</li> 48 <li>If you are developing a new application, please develop against 49 libxml2(-devel)</li> 50 </ul> 51 <p></p> 52 </li> 53 <li><em>I can't install the libxml package, it conflicts with libxml0</em> 54 <p>You probably have an old libxml0 package used to provide the shared 55 library for libxml.so.0, you can probably safely remove it. The libxml 56 packages provided on <a href="ftp://xmlsoft.org/libxml2/">xmlsoft.org</a> provide 57 libxml.so.0</p> 58 </li> 59 <li><em>I can't install the libxml(2) RPM package due to failed 60 dependencies</em> 61 <p>The most generic solution is to re-fetch the latest src.rpm , and 62 rebuild it locally with</p> 63 <p><code>rpm --rebuild libxml(2)-xxx.src.rpm</code>.</p> 64 <p>If everything goes well it will generate two binary rpm packages (one 65 providing the shared libs and xmllint, and the other one, the -devel 66 package, providing includes, static libraries and scripts needed to build 67 applications with libxml(2)) that you can install locally.</p> 68 </li> 69</ol><h3><a name="Compilatio" id="Compilatio">Compilation</a></h3><ol> 70 <li><em>What is the process to compile libxml2 ?</em> 71 <p>As most UNIX libraries libxml2 follows the "standard":</p> 72 <p><code>gunzip -c xxx.tar.gz | tar xvf -</code></p> 73 <p><code>cd libxml-xxxx</code></p> 74 <p><code>./configure --help</code></p> 75 <p>to see the options, then the compilation/installation proper</p> 76 <p><code>./configure [possible options]</code></p> 77 <p><code>make</code></p> 78 <p><code>make install</code></p> 79 <p>At that point you may have to rerun ldconfig or a similar utility to 80 update your list of installed shared libs.</p> 81 </li> 82 <li><em>What other libraries are needed to compile/install libxml2 ?</em> 83 <p>Libxml2 does not require any other library, the normal C ANSI API 84 should be sufficient (please report any violation to this rule you may 85 find).</p> 86 <p>However if found at configuration time libxml2 will detect and use the 87 following libs:</p> 88 <ul> 89 <li><a href="http://www.info-zip.org/pub/infozip/zlib/">libz</a> : a 90 highly portable and available widely compression library.</li> 91 <li>iconv: a powerful character encoding conversion library. It is 92 included by default in recent glibc libraries, so it doesn't need to 93 be installed specifically on Linux. It now seems a <a href="http://www.opennc.org/onlinepubs/7908799/xsh/iconv.html">part 94 of the official UNIX</a> specification. Here is one <a href="http://www.gnu.org/software/libiconv/">implementation of the 95 library</a> which source can be found <a href="ftp://ftp.ilog.fr/pub/Users/haible/gnu/">here</a>.</li> 96 </ul> 97 <p></p> 98 </li> 99 <li><em>Make check fails on some platforms</em> 100 <p>Sometimes the regression tests' results don't completely match the 101 value produced by the parser, and the makefile uses diff to print the 102 delta. On some platforms the diff return breaks the compilation process; 103 if the diff is small this is probably not a serious problem.</p> 104 <p>Sometimes (especially on Solaris) make checks fail due to limitations 105 in make. Try using GNU-make instead.</p> 106 </li> 107 <li><em>I use the SVN version and there is no configure script</em> 108 <p>The configure script (and other Makefiles) are generated. Use the 109 autogen.sh script to regenerate the configure script and Makefiles, 110 like:</p> 111 <p><code>./autogen.sh --prefix=/usr --disable-shared</code></p> 112 </li> 113 <li><em>I have troubles when running make tests with gcc-3.0</em> 114 <p>It seems the initial release of gcc-3.0 has a problem with the 115 optimizer which miscompiles the URI module. Please use another 116 compiler.</p> 117 </li> 118</ol><h3><a name="Developer" id="Developer">Developer</a> corner</h3><ol> 119 <li><em>Troubles compiling or linking programs using libxml2</em> 120 <p>Usually the problem comes from the fact that the compiler doesn't get 121 the right compilation or linking flags. There is a small shell script 122 <code>xml2-config</code> which is installed as part of libxml2 usual 123 install process which provides those flags. Use</p> 124 <p><code>xml2-config --cflags</code></p> 125 <p>to get the compilation flags and</p> 126 <p><code>xml2-config --libs</code></p> 127 <p>to get the linker flags. Usually this is done directly from the 128 Makefile as:</p> 129 <p><code>CFLAGS=`xml2-config --cflags`</code></p> 130 <p><code>LIBS=`xml2-config --libs`</code></p> 131 </li> 132 <li><em>I want to install my own copy of libxml2 in my home directory and 133 link my programs against it, but it doesn't work</em> 134 <p>There are many different ways to accomplish this. Here is one way to 135 do this under Linux. Suppose your home directory is <code>/home/user. 136 </code>Then:</p> 137 <ul> 138 <li>Create a subdirectory, let's call it <code>myxml</code></li> 139 <li>unpack the libxml2 distribution into that subdirectory</li> 140 <li>chdir into the unpacked distribution 141 (<code>/home/user/myxml/libxml2 </code>)</li> 142 <li>configure the library using the "<code>--prefix</code>" switch, 143 specifying an installation subdirectory in 144 <code>/home/user/myxml</code>, e.g. 145 <p><code>./configure --prefix /home/user/myxml/xmlinst</code> {other 146 configuration options}</p> 147 </li> 148 <li>now run <code>make</code> followed by <code>make install</code></li> 149 <li>At this point, the installation subdirectory contains the complete 150 "private" include files, library files and binary program files (e.g. 151 xmllint), located in 152 <p><code>/home/user/myxml/xmlinst/lib, 153 /home/user/myxml/xmlinst/include </code> and <code> 154 /home/user/myxml/xmlinst/bin</code></p> 155 respectively.</li> 156 <li>In order to use this "private" library, you should first add it to 157 the beginning of your default PATH (so that your own private program 158 files such as xmllint will be used instead of the normal system 159 ones). To do this, the Bash command would be 160 <p><code>export PATH=/home/user/myxml/xmlinst/bin:$PATH</code></p> 161 </li> 162 <li>Now suppose you have a program <code>test1.c</code> that you would 163 like to compile with your "private" library. Simply compile it using 164 the command 165 <p><code>gcc `xml2-config --cflags --libs` -o test test.c</code></p> 166 Note that, because your PATH has been set with <code> 167 /home/user/myxml/xmlinst/bin</code> at the beginning, the xml2-config 168 program which you just installed will be used instead of the system 169 default one, and this will <em>automatically</em> get the correct 170 libraries linked with your program.</li> 171 </ul> 172 <p></p> 173 </li> 174 <li><em>xmlDocDump() generates output on one line.</em> 175 <p>Libxml2 will not <strong>invent</strong> spaces in the content of a 176 document since <strong>all spaces in the content of a document are 177 significant</strong>. If you build a tree from the API and want 178 indentation:</p> 179 <ol> 180 <li>the correct way is to generate those yourself too.</li> 181 <li>the dangerous way is to ask libxml2 to add those blanks to your 182 content <strong>modifying the content of your document in the 183 process</strong>. The result may not be what you expect. There is 184 <strong>NO</strong> way to guarantee that such a modification won't 185 affect other parts of the content of your document. See <a href="http://xmlsoft.org/html/libxml-parser.html#xmlKeepBlanksDefault">xmlKeepBlanksDefault 186 ()</a> and <a href="http://xmlsoft.org/html/libxml-tree.html#xmlSaveFormatFile">xmlSaveFormatFile 187 ()</a></li> 188 </ol> 189 <p></p> 190 </li> 191 <li><em>Extra nodes in the document:</em> 192 <p><em>For an XML file as below:</em></p> 193 <pre><?xml version="1.0"?> 194<PLAN xmlns="http://www.argus.ca/autotest/1.0/"> 195<NODE CommFlag="0"/> 196<NODE CommFlag="1"/> 197</PLAN></pre> 198 <p><em>after parsing it with the function 199 pxmlDoc=xmlParseFile(...);</em></p> 200 <p><em>I want to the get the content of the first node (node with the 201 CommFlag="0")</em></p> 202 <p><em>so I did it as following;</em></p> 203 <pre>xmlNodePtr pnode; 204pnode=pxmlDoc->children->children;</pre> 205 <p><em>but it does not work. If I change it to</em></p> 206 <pre>pnode=pxmlDoc->children->children->next;</pre> 207 <p><em>then it works. Can someone explain it to me.</em></p> 208 <p></p> 209 <p>In XML all characters in the content of the document are significant 210 <strong>including blanks and formatting line breaks</strong>.</p> 211 <p>The extra nodes you are wondering about are just that, text nodes with 212 the formatting spaces which are part of the document but that people tend 213 to forget. There is a function <a href="http://xmlsoft.org/html/libxml-parser.html">xmlKeepBlanksDefault 214 ()</a> to remove those at parse time, but that's an heuristic, and its 215 use should be limited to cases where you are certain there is no 216 mixed-content in the document.</p> 217 </li> 218 <li><em>I get compilation errors of existing code like when accessing 219 <strong>root</strong> or <strong>child fields</strong> of nodes.</em> 220 <p>You are compiling code developed for libxml version 1 and using a 221 libxml2 development environment. Either switch back to libxml v1 devel or 222 even better fix the code to compile with libxml2 (or both) by <a href="upgrade.html">following the instructions</a>.</p> 223 </li> 224 <li><em>I get compilation errors about non existing 225 <strong>xmlRootNode</strong> or <strong>xmlChildrenNode</strong> 226 fields.</em> 227 <p>The source code you are using has been <a href="upgrade.html">upgraded</a> to be able to compile with both libxml 228 and libxml2, but you need to install a more recent version: 229 libxml(-devel) >= 1.8.8 or libxml2(-devel) >= 2.1.0</p> 230 </li> 231 <li><em>Random crashes in threaded applications</em> 232 <p>Read and follow all advices on the <a href="threads.html">thread 233 safety</a> page, and make 100% sure you never call xmlCleanupParser() 234 while the library or an XML document might still be in use by another 235 thread.</p> 236 </li> 237 <li><em>The example provided in the web page does not compile.</em> 238 <p>It's hard to maintain the documentation in sync with the code 239 <grin/> ...</p> 240 <p>Check the previous points 1/ and 2/ raised before, and please send 241 patches.</p> 242 </li> 243 <li><em>Where can I get more examples and information than provided on the 244 web page?</em> 245 <p>Ideally a libxml2 book would be nice. I have no such plan ... But you 246 can:</p> 247 <ul> 248 <li>check more deeply the <a href="html/libxml-lib.html">existing 249 generated doc</a></li> 250 <li>have a look at <a href="examples/index.html">the set of 251 examples</a>.</li> 252 <li>look for examples of use for libxml2 function using the Gnome code 253 or by asking on Google.</li> 254 <li><a href="http://svn.gnome.org/viewvc/libxml2/trunk/">Browse 255 the libxml2 source</a> , I try to write code as clean and documented 256 as possible, so looking at it may be helpful. In particular the code 257 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 258 provide good examples of how to do things with the library.</li> 259 </ul> 260 <p></p> 261 </li> 262 <li><em>What about C++ ?</em> 263 <p>libxml2 is written in pure C in order to allow easy reuse on a number 264 of platforms, including embedded systems. I don't intend to convert to 265 C++.</p> 266 <p>There is however a C++ wrapper which may fulfill your needs:</p> 267 <ul> 268 <li>by Ari Johnson <ari@btigate.com>: 269 <p>Website: <a href="https://libxmlplusplus.github.io/libxmlplusplus/">https://libxmlplusplus.github.io/libxmlplusplus/</a></p> 270 <p>Download: <a href="https://download.gnome.org/sources/libxml++/">https://download.gnome.org/sources/libxml++/</a></p> 271 </li> 272 </ul> 273 </li> 274 <li><em>How to validate a document a posteriori ?</em> 275 <p>It is possible to validate documents which had not been validated at 276 initial parsing time or documents which have been built from scratch 277 using the API. Use the <a href="http://xmlsoft.org/html/libxml-valid.html#xmlValidateDtd">xmlValidateDtd()</a> 278 function. It is also possible to simply add a DTD to an existing 279 document:</p> 280 <pre>xmlDocPtr doc; /* your existing document */ 281xmlDtdPtr dtd = xmlParseDTD(NULL, filename_of_dtd); /* parse the DTD */ 282 283 dtd->name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */ 284 285 doc->intSubset = dtd; 286 if (doc->children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd); 287 else xmlAddPrevSibling(doc->children, (xmlNodePtr)dtd); 288 </pre> 289 </li> 290 <li><em>So what is this funky "xmlChar" used all the time?</em> 291 <p>It is a null terminated sequence of utf-8 characters. And only utf-8! 292 You need to convert strings encoded in different ways to utf-8 before 293 passing them to the API. This can be accomplished with the iconv library 294 for instance.</p> 295 </li> 296 <li>etc ...</li> 297</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> 298
