core/net/mac/frame802154: Fix typo in PAN ID compression condition

[jnohlgard]

I stumbled upon this warning when trying out the new GCC 6.1 release:

../../../contiki/core/net/mac/frame802154.c: In function ‘frame802154_has_panid’:
../../../contiki/core/net/mac/frame802154.c:151:30: warning: self-comparison always evaluates to true [-Wtautological-compare]
       if(fcf->dest_addr_mode == fcf->dest_addr_mode) {
                              ^~

I believe this is a typo and that the correct fix is the supplied PR, but please validate this independently.

[simonduq]

I confirm this is a bug, and not the only one. It is something I had seen and fixed before but forgot to upstream it seems.

I think the test should be:
if((fcf->dest_addr_mode == 0) == (fcf->src_addr_mode == 0)) {
(because we don't want equality, we only want both 0 or both non-0)

Then, the next if if(fcf->dest_addr_mode == 0 && fcf->dest_addr_mode == 1) { should basically be removed together with its content.

The third one should also become:
if(fcf->dest_addr_mode == 0 && fcf->src_addr_mode == 0) {

[jnohlgard]

I rewrote the conditions based on table 2a in IEEE 802.15.4e-2012

[jnohlgard]

This condition could never be true

[simonduq]

Right this needs removing as mentioned in my previous comment

[simonduq]

👍

[jnohlgard]

OK to squash?

[alignan]

Yes, please do

[jnohlgard]

squashed

[simonduq]

Thanks!