Re: [avr-gcc-list] assembler macros

[Jamie Lawson]

On Mon, 8 Nov 2004, Johannes Bauer wrote:

> Jamie Lawson wrote:
>
> >
> > #define _NOP() do { __asm__ __volatile__ ("nop") } while (0)
> >
> > What does the "do while(0)" do?
>
> The "do while(0)" thing is frequently being using in macros to open a
> new scope. Usually it's only used when more than one instruction should
> be execute. Imagine:
>

Ahh yes, I see. Thanks.

> However, in your code, I do not see why you would get an error. Line 100
> is the macro-line, I guess? Should the macro maybe read
>
> #define _NOP() do { __asm__ __volatile__ ("nop"); } while (0)
>
> instead of
>
> #define _NOP() do { __asm__ __volatile__ ("nop") } while (0)

You are correct here. It compiles without complaint with your fix.

> Greetings,
> Johannes

Regards,
Jamie Lawson