[Libwebsockets] Assert in output.c

Roger Light roger at atchoo.org
Wed May 7 12:19:12 CEST 2014

Hi there,

I'm trying to integrate libwebsockets into an existing application.
I'm using libwebsockets master as of yesterday, on ubuntu 14.04. I'm
not using SSL.

I've defined a callback for my protocol that implements the
callback only returns 0, nothing else. I haven't yet integrated the
poll handling with my existing poll loop properly. I'm calling
libwebsocket_service(ws_context, 0) after my own poll, which I realise
isn't great but should be fine for testing purposes at the moment.
Buffer size is set to 0, which means 4096, right? In testing I
wouldn't expect them to exceed that number.

I already need to cope with partial writes, so I have code to deal
with that so I'm watching the output of libwebsockets_write() to shift
along my buffer, or not. The buffer has the appropriate padding, so I
presume that on a partial write I can just shift my position along a
bit and retry in the future.

It's also possible/likely that I'll be calling
libwebsocket_callback_on_writable() for a single client multiple times
before the service function is called, and possibly from within the
websockets callback itself.

I haven't been able to pin it down reliably, but I'm occasionally
getting a failed assertion in lws_issue_raw() on line 112 - assert(0).

Am I likely to be doing something stupid, or should this "never
happen"? I can provide more details if needed.



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