------- Comment #48 from mmitchel at gcc dot gnu dot org 2006-02-13 22:42 ------- I'm going to comment on the behavior issue raised in the comments from David Moore, and then review the patch itself.
First, the C standard has nothing to say about this issue; even were it not for the fact that the change only occurs within the scope of #pragma pack, both behaviors are conformant. Second, the ABI standards have nothing to say about this issue, because (so far as I am aware) none of them discuss #pragma pack. If the current behavior (i.e., GCC 4.1 as of today) had been the behavior of GCC for all time, I would not be in favor of making a change -- even though I think the current behavior is peculiar. However, the current behavior is itself a change; we need to resolve the situation once and for all, and we might as well do what seems best. As Michael and I have agreed, it seems to make sense that the zero-width bitfield directives have meaning based on their types; that makes the GNU-extended language (including #pragma pack) more expressive. I understand the user perception/marketing issue around ABI stability, and that's very important to me as well. However, this is very much a corner case (given the fact that #pragma pack is involved), and I think there are sound technical arguments for the change. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22275
