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Table of Content:
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Licensing Terms for libxml
libxml is released under 2 (compatible) licences:
- the LGPL: GNU
Library General Public License
- the W3C
IPR: very similar to the XWindow licence
-
Can I embed libxml in a proprietary application ?
Yes. The W3C IPR allows you to also keep proprietary the changes you
made to libxml, but it would be graceful to provide back bugfixes and
improvements as patches for possible incorporation in the main
development tree
- Unless you are forced to because your application links with a Gnome
library requiring it, Do
Not Use libxml1, use libxml2
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Where can I get libxml
?
The original distribution comes from rpmfind.net or gnome.org
Most linux and Bsd distribution includes libxml, this is probably the
safer way for end-users
David Doolin provides precompiled Windows versions at http://www.ce.berkeley.edu/~doolin/code/libxmlwin32/
-
I see libxml and libxml2 releases, which one should I install ?
- If you are not concerned by any existing backward compatibility
with existing application, install libxml2 only
- If you are not doing development, you can safely install both.
usually the packages libxml and libxml2 are
compatible (this is not the case for development packages)
- If you are a developer and your system provides separate packaging
for shared libraries and the development components, it is possible
to install libxml and libxml2, and also libxml-devel
and libxml2-devel
too for libxml2 >= 2.3.0
- If you are developing a new application, please develop against
libxml2(-devel)
-
I can't install the libxml package it conflicts with libxml0
You probably have an old libxml0 package used to provide the shared
library for libxml.so.0, you can probably safely remove it. Anyway the
libxml packages provided on rpmfind.net provides
libxml.so.0
-
I can't install the libxml(2) RPM package due to failed
dependancies
The most generic solution is to refetch the latest src.rpm , and
rebuild it locally with
rpm --rebuild libxml(2)-xxx.src.rpm
if everything goes well it will generate two binary rpm (one providing
the shared libs and xmllint, and the other one, the -devel package
providing includes, static libraries and scripts needed to build
applications with libxml(2)) that you can install locally.
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What is the process to compile libxml ?
As most UNIX libraries libxml follows the "standard":
gunzip -c xxx.tar.gz | tar xvf -
cd libxml-xxxx
./configure --help
to see the options, then the compilation/installation proper
./configure [possible options]
make
make install
At that point you may have to rerun ldconfig or similar utility to
update your list of installed shared libs.
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What other libraries are needed to compile/install libxml ?
Libxml does not requires any other library, the normal C ANSI API
should be sufficient (please report any violation to this rule you may
find).
However if found at configuration time libxml will detect and use the
following libs:
-
libz
: a highly portable and available widely compression library
- iconv: a powerful character encoding conversion library. It's
included by default on recent glibc libraries, so it doesn't need to
be installed specifically on linux. It seems it's now part
of the official UNIX specification. Here is one implementation
of the library which source can be found here.
-
make check fails on some platforms
Sometime the regression tests results don't completely match the value
produced by the parser, and the makefile uses diff to print the delta. On
some platforms the diff return breaks the compilation process, if the
diff is small this is probably not a serious problem
-
I use the CVS version and there is no configure script
The configure (and other Makefiles) are generated. Use the autogen.sh
script to regenerate the configure and Makefiles, like:
./autogen.sh --prefix=/usr --disable-shared
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I have troubles when running make tests with gcc-3.0
It seems the initial release of gcc-3.0 has a problem with the
optimizer which miscompiles the URI module. Please use another
compiler
-
xmlDocDump() generates output on one line
libxml will not invent spaces in the content of a
document since all spaces in the content of a document are
significant. If you build a tree from the API and want
indentation:
- the correct way is to generate those yourself too
- the dangerous way is to ask libxml to add those blanks to your
content modifying the content of your document in the
process. The result may not be what you expect. There is
NO way to guarantee that such a modification won't
impact other part of the content of your document. See xmlKeepBlanksDefault
() and xmlSaveFormatFile
()
- Extra nodes in the document:
For a XML file as below:
<?xml version="1.0"?>
<PLAN xmlns="http://www.argus.ca/autotest/1.0/">
<NODE CommFlag="0"/>
<NODE CommFlag="1"/>
</PLAN>
after parsing it with the function
pxmlDoc=xmlParseFile(...);
I want to the get the content of the first node (node with the
CommFlag="0")
so I did it as following;
xmlNodePtr pode;
pnode=pxmlDoc->children->children;
but it does not work. If I change it to
pnode=pxmlDoc->children->children->next;
then it works. Can someone explain it to me.
In XML all characters in the content of the document are significant
including blanks and formatting line breaks.
The extra nodes you are wondering about are just that, text nodes with
the formatting spaces wich are part of the document but that people tend
to forget. There is a function xmlKeepBlanksDefault
() to remove those at parse time, but that's an heuristic, and its
use should be limited to case where you are sure there is no
mixed-content in the document.
-
I get compilation errors of existing code like when accessing
root or childs fields of nodes
You are compiling code developed for libxml version 1 and using a
libxml2 development environment. Either switch back to libxml v1 devel or
even better fix the code to compile with libxml2 (or both) by following the instructions.
-
I get compilation errors about non existing
xmlRootNode or xmlChildrenNode
fields
The source code you are using has been upgraded to be able to compile with both libxml
and libxml2, but you need to install a more recent version:
libxml(-devel) >= 1.8.8 or libxml2(-devel) >= 2.1.0
-
XPath implementation looks seriously broken
XPath implementation prior to 2.3.0 was really incomplete, upgrade to
a recent version, the implementation and debug of libxslt generated fixes
for most obvious problems.
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The example provided in the web page does not compile
It's hard to maintain the documentation in sync with the code
<grin/> ...
Check the previous points 1/ and 2/ raised before, and send
patches.
-
Where can I get more examples and informations than in the web
page
Ideally a libxml book would be nice. I have no such plan ... But you
can:
- What about C++ ?
libxml is written in pure C in order to allow easy reuse on a number
of platforms, including embedded systems. I don't intend to convert to
C++.
There is however a C++ wrapper provided by Ari Johnson
<ari@btigate.com> which may fullfill your needs:
Website: http://lusis.org/~ari/xml++/
Download: http://lusis.org/~ari/xml++/libxml++.tar.gz
- How to validate a document a posteriori ?
It is possible to validate documents which had not been validated at
initial parsing time or documents who have been built from scratch using
the API. Use the xmlValidateDtd()
function. It is also possible to simply add a Dtd to an existing
document:
xmlDocPtr doc; /* your existing document */
xmlDtdPtr dtd = xmlParseDTD(NULL, filename_of_dtd); /* parse the DTD */
dtd->name = xmlStrDup((xmlChar*)"root_name"); /* use the given root */
doc->intSubset = dtd;
if (doc->children == NULL) xmlAddChild((xmlNodePtr)doc, (xmlNodePtr)dtd);
else xmlAddPrevSibling(doc->children, (xmlNodePtr)dtd);
- etc ...
Daniel Veillard
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