Calling DDLogError on background thread causes EXC_BAD_INSTRUCTION

[brewpoo]

I know CocoaLumberjack is thread safe but I have been having this issue. Basically, I spawn off a thread using GCD

    dispatch_queue_t queue = dispatch_queue_create("somethread-name", NULL);
    dispatch_queue_t main = dispatch_get_main_queue();
    dispatch_async(queue, ^{
        NSDictionary *response = [WebServiceController getData];
        dispatch_async(main, ^{
            [self processResponse:response];
        });
    });

Within [WebServiceController getData] I call DDLogError when there is an error and this throws EXC_BAD_INSTRUCTION when running in the Simulator. On a device it throws EXC_BREAKPOINT(code=EXC_ARM_BREAKPOINT, subcode=0xdefe). Any suggestions for troubleshooting the issue?

[brewpoo]

Found a workaround by turning on exception break point. Was throwing error in DDLog.m:

#pragma clang diagnostic push
        #pragma clang diagnostic ignored "-Wdeprecated-declarations"
        // The documentation for dispatch_get_current_queue() states:
        //
        // > [This method is] "recommended for debugging and logging purposes only"...
        //
        // Well that's exactly how we're using it here. Literally for logging purposes only.
        // However, Apple has decided to deprecate this method anyway.
        // However they have not given us an alternate version of dispatch_queue_get_label() that
        // automatically uses the current queue, thus dispatch_get_current_queue() is still required.
        // 
        // If dispatch_get_current_queue() disappears, without a dispatch_queue_get_label() alternative,
        // Apple will have effectively taken away our ability to properly log the name of executing dispatch queue.

        dispatch_queue_t currentQueue = dispatch_get_current_queue();  // <- CRASHES HERE
        #pragma clang diagnostic pop

        queueLabel = dd_str_copy(dispatch_queue_get_label(currentQueue));

        threadName = [[NSThread currentThread] name];

Changed to:

#pragma clang diagnostic push
        #pragma clang diagnostic ignored "-Wdeprecated-declarations"
        // The documentation for dispatch_get_current_queue() states:
        //
        // > [This method is] "recommended for debugging and logging purposes only"...
        //
        // Well that's exactly how we're using it here. Literally for logging purposes only.
        // However, Apple has decided to deprecate this method anyway.
        // However they have not given us an alternate version of dispatch_queue_get_label() that
        // automatically uses the current queue, thus dispatch_get_current_queue() is still required.
        // 
        // If dispatch_get_current_queue() disappears, without a dispatch_queue_get_label() alternative,
        // Apple will have effectively taken away our ability to properly log the name of executing dispatch queue.

        //dispatch_queue_t currentQueue = dispatch_get_current_queue();
        #pragma clang diagnostic pop

        //queueLabel = dd_str_copy(dispatch_queue_get_label(currentQueue));

        threadName = [[NSThread currentThread] name];

And no longer crashes...

[desplesda]

I'm getting this error as well, and my workaround was the same.

I just tested this:

dispatch_queue_t backgroundQueue = dispatch_queue_create("Background Queue", DISPATCH_QUEUE_SERIAL);
dispatch_async(backgroundQueue, ^{
    dispatch_get_current_queue();
});

It crashes on the call to dispatch_get_current_queue(). So I don't think that the error is in CocoaLumberjack, but rather in GCD itself.

[desplesda]

A followup: if I get a queue using dispatch_get_global_queue, rather than creating a new one, the crash doesn't occur.

[sourabhletsgomo]

const double delayInSeconds = 1.0;
dispatch_time_t popTime = dispatch_time(DISPATCH_TIME_NOW, delayInSeconds * NSEC_PER_SEC);

__block GSCall *call_ = _call;
dispatch_after(popTime, dispatch_get_main_queue(), ^(void){

    [call_ begin];
});

after this it gives error

[dan55304]

I too have this problem. Is commenting out the queueLabel line the preferred solution? What's the effect of doing this?
** Update: I still get the crash even if commenting out the queueLabel line

[bpoplauschi]

#121 should fix this