Re: [libmicrohttpd] Memory leak?

[Christian Grothoff]

Hi Erik,

Based on your code, I can clearly see that the callback is called, but 
obviously with the wrong address. However, the MHD code internally clearly 
uses the right address, so the best explanation for the difference would be 
some kind of memory corruption going on in between.  Have you tried valgrind 
on your code?  Again, if you can produce a stand-alone *compiling* example 
where the issue still arises, I'll be happy to take another look, but so far 
this seems to be most likely a bug in the rest of your C++ code.  The way you 
use the API (from what I can see) seems to be fine.

Happy hacking!

Christian

On Sunday, October 31, 2010 12:00:20 pm Erik Slagter wrote:
> > Other than that, even after a look at the code I cannot explain what
> > you're experiencing (a testcase would be very welcome...).
> 
> With r13472 (today) I am having the same issue. Here follow some code
> excerpts. Sorry for the lousy layout due to mail formatting.
> 
> I hope this makes sense.
> 
> /* start function */
> 
> /* ... */
> 
> daemon = MHD_start_daemon(MHD_USE_THREAD_PER_CONNECTION | MHD_USE_IPv6
> 
>       | MHD_USE_DEBUG,
> 
>       tcp_port, 0, 0, &HttpServer::access_handler_callback, this,
>       MHD_OPTION_NOTIFY_COMPLETED,
>       &HttpServer::callback_request_completed, this,
>       MHD_OPTION_END);
> 
> /* ... */
> 
> /* access handler callback */
> 
> int HttpServer::access_handler_callback(void * void_http_server,
>               struct MHD_Connection * connection,
>               const char * url, const char * method,
>               const char * version,
>               const char * upload_data, size_t * upload_data_size,
>               void ** con_cls)
> {
>       HttpServer * http_server = (HttpServer *)void_http_server;
> 
>       if(*con_cls == 0)
>       {
>               ConnectionData * ncd = new(ConnectionData);
>               ncd->callback_count = 0;
>               ncd->postprocessor =
>                       MHD_create_post_processor(connection, 1024,
>                               callback_postdata_iterator, ncd);
>               ncd->magic = ConnectionData::connection_data_magic;
>               *con_cls = (void *)ncd;
>               fprintf(stderr, "*** new ConnectionData, con_cls = %p,"
>                       "*con_cls = %p\n", con_cls, *con_cls);
>       }
>       else
>       {
>               (**(ConnectionData **)con_cls).callback_count++;
>               fprintf(stderr, "*** update ConnectionData, con_cls ="
>                       " %p, *con_cls = %p, count = %d\n",
>                       con_cls, *con_cls,
>               (**(ConnectionData **)con_cls).callback_count);
>       }
> 
>       /* ... */
> 
> 
> /* request completed callback */
> 
> void * HttpServer::callback_request_completed(void * cls,
>       void ** con_cls, struct MHD_Connection *,
>       enum MHD_RequestTerminationCode)
> {
>       fprintf(stderr, "*** callback_request_completed\n");
>       fprintf(stderr, "*** cls = %p, con_cls = %p, *con_cls = %p\n",
>               cls, con_cls, con_cls ? *con_cls : con_cls);
> 
>       if(con_cls && *con_cls)
>       {
>               ConnectionData * cdp = (ConnectionData *)*con_cls;
> 
>               if(cdp->magic == ConnectionData::connection_data_magic)
>               {
>                       if(cdp->postprocessor)
>                       {
>                               MHD_destroy_post_processor
>                                       (cdp->postprocessor);
>                               cdp->postprocessor = 0;
>                       }
> 
>                       fprintf(stderr, "*** delete ConnectionData\n");
>                       delete(cdp);
>               }
>               else
>                       vlog("HttpServer::callback_request_compled: invalid 
> magic number 
in
> ConnectionData\n");
> 
>               *con_cls = 0;
>       }
> 
>       return(0);
> }
> 
> /* output */
> 
> *** new ConnectionData, con_cls = 0x7f0eac0008e8, *con_cls = 0x7f0ea4008900
> *** update ConnectionData, con_cls = 0x7f0eac0008e8, *con_cls =
> 0x7f0ea4008900, count = 1
> *** update ConnectionData, con_cls = 0x7f0eac0008e8, *con_cls =
> 0x7f0ea4008900, count = 2
> *** callback_request_completed
> *** cls = 0x136fc00, con_cls = 0x7f0eac0008c0, *con_cls = (nil)
> *** new ConnectionData, con_cls = 0x7f0eac0008e8, *con_cls = 0x7f0ea4008f40
> *** update ConnectionData, con_cls = 0x7f0eac0008e8, *con_cls =
> 0x7f0ea4008f40, count = 1
> *** update ConnectionData, con_cls = 0x7f0eac0008e8, *con_cls =
> 0x7f0ea4008f40, count = 2
> *** callback_request_completed
> *** cls = 0x136fc00, con_cls = 0x7f0eac0008c0, *con_cls = (nil)