[libmicrohttpd] request callbacks

[Eivind Sarto]

I am running into problems with my MHD server.  I may be confusing the order of 
the various callback functions.
As a result, my server sometimes will sometimes de-reference and allocated 
structure after it has been freed.

I allocate a private data structure in the default_handler, and free it in the 
notify_complete handler.
This generally works fine with most requests.   However, if MHD enforces a 
connection timeout I will
get a call to the request MHD_ContentReaderCallback function after the 
notify_complete has been called.

That means the MHD_ContentReaderCallback function cannot access any data 
allocated in the default_handler.
That is why my server sometimes crashes when a connection has been timed out.

My question is what is the order that these 3 callback functions are called 
(default_handler, notify_complete, MHD_ContentReaderCallback)
and if I allocate local data in the default_handler, where do I free it?

Note: I have several different ways to process a request.  Some request use a 
MHD_ContentReaderCallback and some do not.
So I cannot free the data allocated in the default_handler in the  
MHD_ContentReaderCallback.

Thanks,
-eivind