Nios II Eclipse Variable Watchpoint Not Working

Altera_Forum · ‎09-29-2010

I have never been able to get variable watchpoints to work correctly. For example, I have a function something like

int run_test()

{

int retval = 0;

if(a)

retval = 1;

if(!b)

retval = 1;

if(b && c)

retval = 1;

return retval;

}

In Eclipse, if I put a watchpoint on retval and check the Write box, I expect the program to stop any time retval is written. However, I often get to the bottom of the function, retval has been written to a 1, and the program never stopped to tell me where it was happening. Has anyone else had this problem, and is there maybe some setting I'm missing? Thanks.

Altera_Forum · ‎09-30-2010

You need to be using one of the more advanced version of the Nios core.

On the page where you select the level of pipelining, MMU, and other such things, I think there is a description that says which versions support variable watch points. Select that and I think it will work.

Altera_Forum · ‎09-30-2010

Data watchpoints won't work on items that the compiler assigns to a register, only on writes to real memory.

Even without the optimiser it is possible that 'retval' doesn't exist as a memory item (or at least the allocated item isn't used.

If you move 'retval' outside the function and define it as 'volatile int retval' then the writes are required to be generated and the watchpoint should trap.

Altera_Forum · ‎09-30-2010

Those are both excellent answers. Thank you, I will look into it.