[Adium-devl] g_string_free() and me (aka gaim [17165] doesn't like Adium)

[Evan Schoenberg]

Sigh, I'll commit this whenever trac and svn decide to work again.  I  
can't keep checking, so if someone would email me or text message me  
when they're up, I'd appreciate it.

On Sep 11, 2006, at 4:49 PM, Evan Schoenberg wrote:

> Okay, found the problem and fixed it.  What a headache.
>
> The problem was purely in Adium's adiumGaimEventloop code... but  
> nothing before [17165] had ever triggered the exact situation,  
> which was:
> 1) Non-blocking write condition triggers its socket callback
> 2) That socket callback triggers a prpl callback which adds a read  
> condition on the same fd
> 3) That socket callback does a gaim_source_remove() on the write  
> callback's tag
> 4) That socket callback then free()'s the data associated with the  
> write callback (but not the read callback, obviously)
>
>
> (2) means that the socket was converted from write-only to read/ 
> write (because the write condition hadn't yet been  removed.
> (3) then removed the write part of the read/write... which in code  
> that had previously never been touched (and was written when I was  
> fixing our handling of nonblocking sockets in the first place),  
> called CFSocketDisableCallBacks(socket, kCFSocketWriteCallBack) so  
> that the socket would remain around but only trigger for the next  
> read condition.
>
> Unfortunately, CFSocketDisableCallBacks() appears to be a no-op....  
> the socket callback was indeed called again, with a write callback  
> signature, as soon as data was available to be written.  This  
> triggered a return to (1) above... which besides wrecking havoc on  
> the connect process (you could see this in Jabber's "Connected."  
> message appearing twice in rapid succession) led to a double-free()  
> at (4).
>
> Disabling the auto-reenabling of callbacks with CFSocketSetFlags()  
> before calling CFSocketDisableCallBacks() doesn't make a difference.
>
> Solution: Invalidate, release, and create from scratch the socket  
> when converting from read/write to read-only or write-only.  This  
> mirrors how we convert a read-only or write-only socket to read/ 
> write in the first place.
>
> -Evan
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