Hi, Derek Xiang,
After I modified your code, I can debug your code as the screenshot.
As I said, if you create a project based on Quick Start tools, you have to load the GCT and setting the GCT correctly.

Enable GPIOF gated clock in GCT tools

//set up GPIOF8 pin as output

//add the code in while(1):
ioctlGPIO_SET_PIN(GPIO_F,BIT_8);
ioctlGPIO_CLEAR_PIN(GPIO_F,BIT_8);
