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On 30/11/13 20:15, Russell King - ARM Linux wrote:
From: Russell King rmk+kernel@arm.linux.org.uk
The following errors were observed on ARM during a randconfig build. This patch addresses them by ensuring that the batadv_header structure is appropriately packed; this structure contains three 8-bit elements so there should be no undesired side effect from this packing.
net/batman-adv/main.c: In function 'batadv_init': net/batman-adv/main.c:425:279: error: call to '__compiletime_assert_425' declared with attribute error: BUILD_BUG_ON failed: offsetof(struct batadv_unicast_4addr_packet, src) != 10 net/batman-adv/main.c:426:267: error: call to '__compiletime_assert_426' declared with attribute error: BUILD_BUG_ON failed: offsetof(struct batadv_unicast_packet, dest) != 4 net/batman-adv/main.c:427:275: error: call to '__compiletime_assert_427' declared with attribute error: BUILD_BUG_ON failed: offsetof(struct batadv_unicast_tvlv_packet, dst) != 4 net/batman-adv/main.c:428:261: error: call to '__compiletime_assert_428' declared with attribute error: BUILD_BUG_ON failed: offsetof(struct batadv_frag_packet, dest) != 4 net/batman-adv/main.c:429:271: error: call to '__compiletime_assert_429' declared with attribute error: BUILD_BUG_ON failed: offsetof(struct batadv_icmp_packet, icmph.dst) != 4 net/batman-adv/main.c:430:277: error: call to '__compiletime_assert_430' declared with attribute error: BUILD_BUG_ON failed: offsetof(struct batadv_icmp_packet_rr, icmph.dst) != 4
Signed-off-by: Russell King rmk+kernel@arm.linux.org.uk --- net/batman-adv/packet.h | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/net/batman-adv/packet.h b/net/batman-adv/packet.h index 207459b62966..4039f25794e0 100644 --- a/net/batman-adv/packet.h +++ b/net/batman-adv/packet.h @@ -171,7 +171,7 @@ struct batadv_header { /* the parent struct has to add a byte after the header to make * everything 4 bytes aligned again */ -}; +} __attribute__((packed));
Russell,
this attribute was there in the past and then was removed on purpose because on some architectures it makes the compiler generating very inefficient code (you can check http://article.gmane.org/gmane.org.freifunk.batman/8317 for more details).
So we removed the __packed attribute and we took care of properly aligning all the structures by adding "alignment/reserved members" when needed.
I don't know the ARM architecture at all (I don't know if the other batman-adv developers do), so could you please provide here some more details about why that static check is failing? We would like to address this issue differently rather than re-adding the __packed attribute.
Thanks a lot.
Best Regards,
- -- Antonio Quartulli