After discussions in multiple meetings, we finally reached a point back in April where I could merge Walter's bitfields DIP and submit it to Atila for the final decision.

The DIP was accepted based on the following rationale.

Bitfields are useful in the following cases:

1. minimizing memory consumption in a struct;
2. creating binary-compatible data structures between D and C or C++;
3. conforming a struct layout to external requirements, such as a hardware register.

This DIP adopts the C and C++ syntax because of its simplicity. A persistent objection to the proposal was that C's bitfield layout is implementation defined. Proposals to implement a D-portable layout and special-case the C-defined layout suffered from unattractive syntax, so were not adopted.

In practice, layouts are consistent on each platform, but can vary between platforms. This is irrelevant for Cases 1 and 2. For Case 3, in the rare cases where the layout may become a problem, it is easy to work around by specifying a bitfield to match any layout, and by employing shifting and masking as necessary.

This is a purely additive feature that should break no existing code.

https://github.com/dlang/DIPs/blob/master/DIPs/accepted/DIP1051.md