Question

Xcode’s “thread list” pane shows English-like names for several special threads: com.apple.main-thread, com.apple.libdispatch-manager, com.dispatchfractal.opencl, com.dispatchfractal.opengl, com.apple.root.low-priority,… But for user-created threads that field is just blank.

Is there any way to set that “thread name” field programmatically from my application? For example, if I’ve got a thread devoted to network I/O, I’d like it to show up as “com.example.network-io” in the debugger; if I spawn five worker threads I’d like to be able to name them “worker A”, “worker B”, etc. Does Xcode pull its thread-names from some API that I could hook into myself? Maybe something like CFAssignDebuggerNameToCurrentThread? 🙂

Answer 1

Probably not exactly what you want but NSThread has setName: method that allows you to set thread’s name, you can attach meaningful name to the thread so you’ll get the following in debugger:

[[NSThread mainThread] setName:@"That is main thread!"];

Remember also that some apis (like grand central dispatch) operate with thread pools so you are not guaranteed on what thread your operation will be performed

Edit:
com.apple.main-thread, com.apple.libdispatch-manager etc are labels of corresponding dispatch queues. You can set label value when queue is created with dispatch_queue_create function and later get it from the queue using dispatch_queue_get_label function.

It seems there’s no API to change label value of the existing dispatch queue and I would not advise to change labels of the system queues anyway.