DIP: add Bit Fields

[Dennis]

On Monday, 11 March 2024 at 18:12:58 UTC, Walter Bright wrote:
> On 3/9/2024 1:41 AM, Dennis wrote:
> which is 64 bits. That should produce the same result across 
> different C compilers, i.e. it shouldn't be a problem.

That's great, but it's not what the DIP says currently, which is 
that the layout (for non-int) is implementation defined matching 
a C compiler.

It makes the comparison with C's varying `int` size, but the 
difference is that in that case, D sticks to its guns and keeps 
`int` 32-bits even when C would make it 16-bit. Perhaps the DIP 
could say: the layout in D is defined as X, which follows what C 
compilers do in practice.

Then programmers can be comfortable relying on the layout.

> The D compiler itself would, so using it in the D front end 
> will effortlessly work with the C++ gdc and ldc backends.

Those are extern(C++) classes, and they already have working 
bitfields. They wouldn't be impaired by making bit fields in D 
consistent and predictable.