iOS：CGContextStrokePath（context）在iOS 12中使用EXC_BAD_ACCESS崩溃

Question

我正在尝试使用CALayer和CGContextStrokePath(context)来绘制签名，但是它仅在iOS 12中因以下错误而棘手崩溃：

  

malloc：已释放对象0x1196538c8的校验和不正确：可能   释放后修改。       损坏的值：0x4069e00000000000       （899,0x17190b000）malloc：***在malloc_error_break中设置一个断点进行调试

代码段：

- (void)drawLayer:(CATiledLayer *)layer inContext:(CGContextRef)contx {
    if (layer == canvasLayer) {
        //we don't want this to fire after the background layer update
        //and after the path has been released
        if (!touching) return;
        CGContextAddPath(contx, path);
        CGContextSetLineWidth(contx, 7.0f);
        CGContextStrokePath(contx);
    }
    else if (layer == bckLayer) {
        CGContextSaveGState(contx);
        CGContextTranslateCTM(contx, 0, backgroundLayer.bounds.size.height);
        CGContextScaleCTM(contx, 1.0, -1.0);
        CGImageRef ref = cacheImage.CGImage;
        CGContextDrawImage(contx, backgroundLayer.bounds, ref);
        CGContextRestoreGState(ctx);
    }
}