[avr-gcc-list] assembler macros

[Jamie Lawson]

Hi,

I've just returned to a year old avrgcc project to apply a small
modification and tried avr-glibc-cvs-20041028 (gcc-3.4.2, binutils-2.14 +
patches).

I had been using code such as

void settle_delay(uint8_t n) {

    uint8_t x;

    for (x = 0; x <= n; x++) {
        _NOP();
    }
}

which gives me the following error:

io.c: In function `settle_delay':
io.c:100: error: parse error before '}' token

In avr-glibc-1.0.4 I see _NOP() is defined as:

#define _NOP __asm__ __volatile__ ("nop")

In this post 1.0.4 avr-glibc I see _NOP() is defined as:

#define _NOP() do { __asm__ __volatile__ ("nop") } while (0)

How do I use this new version properly to avoid the error?

What does the "do while(0)" do?

Regards,
Jamie Lawson