DIP 1051--"Add Bitfields to D"--Formal Assessment

[Mike Parker]

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