Re: [avr-gcc-list] Check whether two macros are equal to each other

[Joerg Wunsch]

Georg-Johann Lay <address@hidden> wrote:

>> Could anyone explain this to me? Is there any way around this
>> (still using macros)?

> With macros? No way here.

Well: no way *at the preprocessor level*.

However, moving the comparison to the *compiler level* could work.
The values of e.g. DDRD and DDRB are expressions that can be compared
by the compiler.  As the resulting comparison is constant at
compile-time, with optimization enabled, those code portions that can
never be reached (due to the compile-time constant comparisons) are
optimized away.

So, turn your

#if LED1_DDR == LED2_DDR

into

  if (LED1_DDR == LED2_DDR) {
    // ...
  } else {
    // both DDRs are not the same
    // ...
  }

-- 
cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)