UIImage extension to create image from string - How to find EXC_BAD_ACCESS cause?

Question

I have created an UIImage extension to create an image from a string (using an icon font). Most of the time it works without any problem, but sometimes it caused the app to crash with a EXC_BAD_ACCESS. This happens both on devices an in the simulator.

How can I find out what is going wrong? Why does it work most of the time and fails only in rare cases?

The code runs on the main thread.

---

extension UIImage {

    static func image(withIconText text: String, font: UIFont, color: UIColor) -> UIImage {            
        #if os(iOS)
            let scale = UIScreen.main.scale
        #else
            // Watch
            let scale = 2.0
        #endif
        
        let attributes = [
            NSAttributedString.Key.font: font,
            NSAttributedString.Key.foregroundColor: color,
        ]
        
        UIGraphicsBeginImageContextWithOptions(CGSize(width: font.pointSize, height: font.pointSize), false, scale)
        
        let textSize = (text as NSString).size(withAttributes: attributes)
        let origin = CGPoint(x: (font.pointSize - textSize.width) / 2, y: (font.pointSize - textSize.height) / 2)
        let rect = CGRect(origin: origin, size: textSize)

        // Crash: Thread 1: EXC_BAD_ACCESS
        text.draw(in: rect, withAttributes: attributes)
        
        let image = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        
        return image ?? UIImage()
    }

}