Main-thread misuse

The main-thread misuse detector reports blocking work done on the main thread — the kind of call that causes stutter and, when it takes long enough, a hang. Each violation is filed as a non-fatal error report with the stack of the call.

Main-thread misuse detection is off by default.

Option key	BugseeOptionDetectAndReportMainThreadMisuse
BugseeOptions property	— (set by key)
Default	NO

Objective-C

BugseeOptions *options = [BugseeOptions defaultOptions];
[options updateLaunchOptions:@{
    BugseeOptionDetectAndReportMainThreadMisuse : @YES,
}];

[Bugsee launchWithToken:@"<your_app_token>" options:options];

Swift

let options = BugseeOptions.default()
options.updateLaunch([
    BugseeOptionDetectAndReportMainThreadMisuse: true,
])

Bugsee.launch(token: "<your_app_token>", options: options)

What gets flagged

Bugsee intercepts these Foundation calls and reports the ones made on the main thread:

Category	Calls	Domain
Disk read	+[NSData dataWithContentsOfFile:], +[NSData dataWithContentsOfURL:] and their options:error: variants	MainThreadMisuse::DiskRead
Disk write	-[NSData writeToFile:atomically:], -[NSData writeToURL:atomically:] and their options:error: variants	MainThreadMisuse::DiskWrite
UserDefaults	-[NSUserDefaults synchronize]	MainThreadMisuse::UserDefaults
Network	+[NSURLConnection sendSynchronousRequest:returningResponse:error:]	MainThreadMisuse::Network

Bugsee's own file access is never reported.

Objective-C entry points only

The detector intercepts the Objective-C methods above, so it does not see:

• Swift's Foundation calls such as Data(contentsOf:), data.write(to:) and String(contentsOfFile:), which do not go through these methods.
• -[NSData initWithContentsOfFile:] and -[NSData initWithContentsOfURL:].
• FileManager / NSFileManager, streams, POSIX file I/O, and a URLSession request waited on with a semaphore.

A clean result does not mean the main thread does no blocking work.

The report

Field	Value
Type	Error (non-fatal), with the error priority (BugseeOptionReportingDefaultErrorPriority)
Summary	Disk read on main thread, Disk write on main thread, UserDefaults access on main thread or Network operation on main thread
Domain	One of the domains above
Stack	The call stack at the violation. The issue is titled after its top frame, the violating call site

Each call site is reported once per session, identified by the first frame of the stack outside the SDK. Stopping Bugsee starts a new session.

On the simulator and Mac Catalyst, the detector installs nothing and reports nothing.