On Mon, Mar 10, 2014 at 02:12:27PM -0700, Gurucharan Shetty wrote: > struct ofpact has enums that are packed in case of __GNUC__. > This packing does not occur for visual studio. For 'struct ofpact_nest', > we are expecting that this structure is less than or equal to 8 bytes > which won't be true in compilers where enums are not packed. > > Signed-off-by: Gurucharan Shetty <gshe...@nicira.com> > --- > There must have been a reason why there was this BUILD_ASSERT in the > first place. But, I do not understand the reason. (Unit tests don't > fail after removing the OVS_PACKED_ENUM macro from the related enums > and this build assert.)
The goal of OFPACT_ALIGNTO is to make sure that every ofpact starts on an 8-byte boundary, which is in turn important because RISC machines often require 8-byte alignment for e.g. pointers. Since ofpact_nest contains nested ofpacts, the ofpact[] array inside it needs to be on an 8-byte boundary too. The build assertion checked for that, but it was too strict: any multiple of 8 bytes will work, but it required exactly 8 bytes. I think that the build assertion should be relaxed from "<offset> == OFPACT_ALIGNTO", to "<offset> % OFPACT_ALIGNTO == 0". Does that make sense? Thanks, Ben. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
