Thread: Subtracting a macro from a pointer

Hi all,

I am trying to subtract the value of a macro from a pointer but after this operation, I still get the same pointer address.

In particular, why the following code

Code:

	struct list_head *init_tasks = tasks;
	printk("init_task next task is: 0x%X\n", init_tasks->next);

gives the same result with this?:

Code:

	init_tasks = (uint8_t*)(init_tasks->next - (uint32_t)SEGMENT_OFFSET);
	printk("init_task next task (phys) is: 0x%X\n", init_tasks);

Could anyone let me know what I am doing wrong?

Thanks in advance.

What is the definition of SEGMENT_OFFSET ?

Also which compiler and OS is this for?

What is tasks??
Basically tasks->next = (uint8_t*)(init_tasks->next - (uint32_t)SEGMENT_OFFSET)
Are you implying this?
Not enough code. WTF is value of init_tasks for 2nd code segment.