Unused variables

[kolio]

Does anybody know how to avoid the unused variables from being mapped into memory?
Is there any level of optimization or another setting that can do this?
Of course, PCWH issues a warning, but the memory is still reserved.
I've checked it with PCH 4.068 (just downloaded) and 3.221.
And the question is NOT related to the "good programming warning-free style"

[ckielstra]

My first suggestion would be to remove all unused variables from your program but you will have figured that out yourself, so can you be a bit more specific as to why that's not possible?

One common 'unused variable' that I know of and is a pain in the *ss is the rs232_errors variable added by the compiler when you have the 'ERRORS' keyword in the rs232 configuration. The following trick was suggested by Bluetooth in this thread.

[kolio]

To be more specific:

1.There are two global variables declared:
volatile word StartTimer, StopTimer;

2.'StopTimer' is never referenced.

3.Output .ERR file:
...
>>> Warning 202 "source.c" Line 20(31,40): Variable never used: StopTimer
...

4.Output .SYM file:
...
1B7-1B8 StartTimer
1B9-1BA StopTimer
1BB MAIN.index
...

5.Output .STA file:
...
RAM used: 452 (29%) at main() level
479 (31%) worst case
...

6.If 'StopTimer' declaration is just deleted, then
output .STA file is:
...
RAM used: 450 (29%) at main() level
477 (31%) worst case
...

Is there any optimization level, where the unused variables will NOT eat up memory, but will be quietly or loudly (thru some warnings) discarded?

P.S. IMHO 'rs232_errors' has a good reason and shold be used instead of ignored. Handling framing and overrun errors is very important, but it's another story.

[Ttelmah]

It is also worth saying, that local variables that a not used, are not really 'mapped into memory'. CCS, is quite smart, and re-uses the memory space in subroutines, so though it may flag a variable as using a particular address, the same address will also be used in other routines above this. The warning, is a warning, not a terminal 'error', so just turning off this error number, may be all that is needed...

Best Wishes

[ckielstra]

What Ttelmah says is true for local variables but I don't think the memory is reused for global variables, at least it wasn't in the v3 compilers.

What I don't understand is why you want to have an unused variable in your source code? Doesn't sound like good programming practice to me, even in a library or something you would place it in conditional code (#ifdef).

[kolio]

Yeah, the good old versions 2.xx...
ckielstra, you're damn right, buddy and you sniffed the problem.
There will be too much #ifdefs, because the product has 7 (yet) firmware profiles and 4 slight h/w differencies (assemble or not some components). One way is just to make for each one a separate set of files, but then any new common feature or fixed bug should be tracked at 7 projects. The other way is to have one common set of files (library) and 7 projects with the specific functionality. And here comes the #ifdef issue...

So, probably according CCS folks, removing unused variables is no longer an optimization problem, but "do-it-yourself" for Ver >= 3.xx.
Don't misunderstand me, I'm using CCS since 2000, last week just bought newest PCH and now little bit dissapointed by them.