Re: [xml] xmlInitParser: Necessary or not?

[Daniel Veillard <veillard redhat com>]

On Fri, Oct 05, 2007 at 08:12:39PM +0200, Ralf Junker wrote:
> Hello,
>
> I understand that xmlCleanupParser should be called to clean up after libxml and free allocated global 
> memory. However, xmlCleanupParser only works if the parser has been previously initialized. The only way to 
> do so is to call xmlInitParser (see source for details).
>
> Now I find that many functions call xmlInitParser automatically (htmlNodeDump, htmlReadMemory, to name but 
> a few) and make xmlCleanupParser work. On the other hand, many functions allocate global variables and do 
> not call xmlInitParser. As a result, xmlCleanupParser will not work. So if an app uses those functions only 
> and does not call xmlInitParser separately, its call to xmlCleanupParser will have no effect and the 
> application will leak memory.
>
> Questions:
>
> * Is it always recommended or even necessary to call xmlInitParser regardless of which functions are used?

  Not needed if you just do a simple parsing as the parsing entry points
are the one with a guard. But call it if you do anything more complex
than 'I just need to parse a file'

> * The documentation suggests to call xmlInitParser "once before processing in case of use in multithreaded 
> programs." As demonstrated above, it might be necessary to call it even in single-threaded programs. Is 
> this not a documentation error?

  I don't think so. The examples call it, actually the examples do something
even better: use LIBXML_TEST_VERSION which does the checking against the
shared lib to make sure there is no versionning problem. And that in 
turn calls xmlInitParser() . 

> * xmlInitParser and xmlCleanupParser cover libxml. Do I need to take care of additional initialization and 
> finalization besides these two in libxml?

  not that I can think of

> * Can I expect similar problems in libxslt, too? Which init/finalize functions should I call for libxslt?

  If you don't plug XSLT extensions (yours or though exsltRegisterAll())
no, except for the security preference functions. See xsltproc.c in the
tarball.

Daniel

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