PR 22275 is about a change in the structure layout used by GCC when #pragma pack is mixed with zero-width bitfields. In particular, in GCC 3.3 and earlier, zero-width bitfields still forced the next element to be placed on an alignment boundary, just as they do in unpacked structures. In GCC 3.4 and later, zero-width bitfields no longer have this effect, when used within a structure.
I believe the older behavior was better. The entire purpose for a zero-width bitfield is to make an alignment request. So, we should assume that if the user wrote that, even within the scope of #pragma pack, they had a reason for doing so. #pragma pack should pack the things that are not explicitly aligned, but it should no more pack the field following a zero-width bitfield than it should a field that has an explicit alignment attribute. As a result, I believe that we should change the behavior back in GCC 4.1. We should not change GCC 3.4.x or GCC 4.0.x because that would be an ABI change within a single release branch. I know this was discussed previously to some extent, but I'm not sure if we reached consensus. I'm going to interpret silence as assent if nobody objects within a few days. So, any disagreements? Thanks, -- Mark Mitchell CodeSourcery, LLC [EMAIL PROTECTED] (650) 331-3385 x713
