Question

I am using Libxml2 to read/write XML files.
For catching libxml errors while loading XML, i am using xmlSetGenericErrorFunc.

void Myclass::load(const std::string &filename)
{
    xmlGenericErrorFunc handler = (xmlGenericErrorFunc) catchErrors;
    xmlSetGenericErrorFunc(this, handler); //context pointer, error handler
}

Resetting the context and error handler can be done as below.

xmlSetGenericErrorFunc(NULL, NULL); 

My wrapper library is used by many processes.
Libxml2 is a .so file.

If i use context pointer in error handler, will there be any probability for a crash if some process dies without resetting the context pointer and parsing error occurs in other process ? can libxml invoke error callback with a dead pointer ?

Any help would be appreciated. Thank you.

Answer 1

After having a look at the source:

First check if libxml is compiled with LIBXML_THREAD_ENABLED. You may check with xmllint -version and it should say: compiled with: Threads ...

xmlSetGenericErrorFunc (from error.c) sets xmlGenericError (defined in globals.h), which (in case threads are enabled) is declared as part of xmlGlobalState structure.

Now the xmlGetGlobalState documentation states clearly that the state is maintained for each thread separately.

So theoretically threads don’t influence one another and you should observe that setting error handler in one thread doesn’t change the behaviour of another thread. And it seems you’re on the safe side.