[avr-gcc-list] Best practice for external variable (newbie-ish question)

[Matthew Smith]

Hi All

I am writing a small programme where I need a couple of variables to be
accessible to various routines, including an ISR.

I have declared the variables in the main body of the programme as
volatile, as I believe that this is required for access by the ISR:

volatile uint8_t foo;
volatile uint8_t bar;

1) Am I correct in thinking that I need to declare this in the ISR thus:

SIGNAL(SIG_OUTPUT_COMPARE1A)
{
        extern uint8_t foo;
        foo++;
        // Other stuff
}

2) Is this the correct way to access it in an ordinary routines, or
should I be doing something with references?

void startclock(void)
{
        extern uint8_t bar;
        // Various stuff
        bar=1;
}

Comments/suggestions would be greatly appreciated.

Cheers

M

-- 
Matthew Smith
Work: <http://www.kbc.net.au> | Home: <http://www.mss.cx>

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