can_fifo_getd.data appearing in symbol file, not called

[dclavette]

Hi All,

First post. I have been tracking down a bug and could use some help to see if others have ever experienced this.

I found an instance where a variable keeping track of my currentTime was smaller than a variable keeping track of a variable keeping track of my lastUpdateTime, i.e the last time this function was completed.

It was concluded that currentTime was overwritten with a smaller value since, at the end of the function, lastUpdateTime was set to currentTime.

Specifically, the last two bytes were changed. Looking in my symbol file I found that the the last two bytes of currentTime, declared in main (and therefore is never out of scope) shares it's lower two bytes with the variables can_fifo_getd.data and can2_fifo_getd.data.

We do not use these functions - can_fifo_getd or can2_fifo_getd. We do, however, use can_getd and can2_getd.

Using compiler version v5.061 using device DSPIC33FJ128GP706A.

Thank you!

[jeremiah]

You might check the ROM portion of the SYM file and see if those two functions also appear there. If so, then something in your code is making them seem like they are being used somewhere.

One potential reason is if you are using function pointers and you take the address to those functions anywhere. You might additionally check and see if any precompiler directives are in play such as #ORG.

As an example:

[dclavette]

jeremiah,

I have checked, those functions (can_fifo_putd and can2_fifo_putd) are not in ROM. Additionally, I am not using any #ORG directives.

Thanks for the suggestions.

[jeremiah]

Given that you cannot provide us a small compilable example of the problem and the description thus far, I would suggest contacting CCS support and suggest it as a possible bug. If the variables are showing up in the sym table but the functions are not, that is odd.

[dclavette]

jeremiah - here is a small, compilable example.

[Ttelmah]

That _isn't_ your problem.....


It is putting the local variable there, because it is not used.
The compiler knows it can place a variable in the same memory, provided
it is not used by one function inside the other. It has the declarations
for the fifo functions, and merrily says 'not used inside main', so I can
put them into the same memory space.
If you called the can_fifo_putd function from anywhere at all, it'd
immediately relocate the variable elsewhere.
So if I modify your example and call can_fifo_putd. it immediately
changes the symbol file to:

[jeremiah]

[Ttelmah]

As a comment, I note that you are using an int64 for 'time'. This means
you must be using a third party 'time' library, since the CCS functions
only use int32. Are you very sure there isn't an issue in this?. What
does it use as it's base time?.