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  • Any argument that could be made against packed structures could also be used to justify making bitfields an optional feature. Accessing members of packed structures would be slow on some processors, fast on others, but having compilers try to replace user-code workarounds for the lack of unaligned-access features with more efficient code is far more complicated than simply having compilers let programmers specify what they need. Commented May 25, 2016 at 15:18
  • @supercat: what are you arguing for (or against)? I don't get it. Commented May 28, 2016 at 13:56
  • I'm of the opinion that bitfields should be optional, but if bitfields are going to be a mandatory feature then it would make sense to extend them in a way that allows explicit control of struct layout. Otherwise, the net effect is that compilers have to do 90% of the work that would be needed for full control of layout, but programmers only reap 10% of the benefit. Commented May 28, 2016 at 17:11
  • @supercat: bit-fields are integers and follow the same bit layout ordering rules as integers: implementation defined. Struct members are ordered on character boundaries as declared, possibly with packing inserted. They are conceptually quite separate. [You'll need to ask another question if you want to expand on your proposal, but I don't think it would work at all.] Commented May 29, 2016 at 14:31