Re: abnormal thread termination

[Richard Frith-Macdonald]

> On 13 Jul 2015, at 09:57, David Chisnall <address@hidden> wrote:
> 
> On 10 Jul 2015, at 20:18, Riccardo Mottola <address@hidden> wrote:
>> 
>> Hi,
>> 
>> I detach a thread "normally" with:
>> 
>> [updateButton setEnabled:NO];
>> [NSThread detachNewThreadSelector:@selector(updateData:) toTarget:self 
>> withObject:nil];
>> 
>> It executes everything as expected, but I continuously get:
>> WARNING thread 0x2c63c1a8 terminated without calling +exit!
>> 
>> I have done something similar with other threads and I don't get this error. 
>> What could be happening? Some sort of premature exit? It executes up to the 
>> last statement.
> 
> This message also appears for threads that are not created with NSThread, 
> which is quite annoying.  I use some of the C++11 threading support for some 
> worker threads and I get a message when they exit.

This message indicates a bug in the program as far as I can tell from looking 
at the source;

It’s generated by the handler set by pthread_key_create() and should only be 
called if the thread exits while the thread-specific data associate with the 
key (ie the NSThread object) is non-null.

When a thread is detached by NSThread, it runs a method and calls +exit when 
the method completes, and +exit destroys the NSThread object and sets the 
thread-specific data to null.
When a non-gnustep thread is used for gnustep code, there are two functions 
provided to register/deregister it (and the latter similarly destroys the 
NSThread instance and nulls-out the thread-specific variable).

So seeing the message means that a thread has somehow exited without cleaning 
up its gnustep related thread-specific data (thus leaking an NSThread instance 
and a presumably other related objects).

I don’t see how that can happen other than by an application level bug (ie some 
code in that thread calls pthread_exit() or something similar).

Of course, I may have missed spotting some race condition or logic error in the 
code ...