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Re: [avr-gcc-list] volatile...

From: Dave Hansen
Subject: Re: [avr-gcc-list] volatile...
Date: Fri, 15 Dec 2006 10:22:44 -0500

From: Paulo Marques <address@hidden>

Graham Davies wrote:
"David Brown" wrote:
You are missing a number of points ...

Well, I think we're getting close to complete coverage now!

Well, since we are going for complete coverage, I'll add my 2 cents, then.

You've opened some new cans of worms here, but I'll only make one small comment


static uint16_t atomic_read_16(uint16_t *ptr)
        uint16_t ret;

        ret = (volatile)(*ptr);

Your cast to volatile here is not only unnecessary, it's wrong. You are actually casting the uint16_t intermediate value to signed int, which is then converted (back) to uint16_t. If you tried to model an atomic_read_32 on this function, you might not like the results.

On newer conmpilers (with C99 compliance) it shouldn't even compile (implied int no longer allowed).


OK, a second comment: I like to save SREG before the CLI, then restore SREG rather than blindly enabling interupts with SEI. That way, if I happen to call the function with interrupts disabled, they aren't unintentionally enabled early.

        return ret;



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