[libmicrohttpd] MHD_OPTION_URI_LOG_CALLBACK and con_cls

[Nicolas Mora]

Hello,

While trying to use the option MHD_OPTION_URI_LOG_CALLBACK to get the 
full url from the client, the documentation says:

"the return value will be passed as (*con_cls) in calls to the 
MHD_AccessHandlerCallback when this request is processed later; 
returning a value of NULL has no special significance (however, note 
that if you return non-NULL, you can no longer rely on the first call to 
the access handler having NULL == *con_cls on entry;)"

The need is to store the full url called by the client in a char * variable.

In my program, I detect the first iteration of MHD_AccessHandlerCallback 
by testing if con_cls is NULL:
https://github.com/babelouest/ulfius/blob/master/src/ulfius.c#L111

Is there another way for MHD_AccessHandlerCallback to detect it's in the 
first iteration, so I can properly use con_cls and the option 
MHD_OPTION_URI_LOG_CALLBACK ?

/Nicolas