• Dave P. (32/32) Oct 17 2022 [Adding bitfields to
• zjh (2/3) Oct 17 2022 For me, the more features, the better.
• test123 (2/14) Oct 17 2022 With d CTFE reflection, this is easy to workaround.

Dave P. <dave287091 gmail.com> writes:

[Adding bitfields to 
D](https://dlang.org/changelog/2.101.0.html#dmd.bitfields) for C 
interop is nice as it will automatically match the platform’s ABI 
for bitfields, but I don’t understand why we would want the 
implementation defined nightmare for regular D bitfields. One of 
the most annoying things about C bitfields is that if you use 
them,  you can’t just write your structs to disk or across the 
network as your format is immediately non-portable across 
different systems. That sucks as that’s exactly when you would 
want to save space with bitfields. Native D bitfields should 
avoid this problem.

However, you should be able to express that your struct including 
bitfields matches the layout of a C struct. I therefore propose 
that we tweak the syntax to require an extern(C) around bitfields 
matching C.

```D
struct A {
     extern(C) {
         int x:3, y:2;
     }
}
```
Or
```D
extern(C)
struct B {
     int x: 3, y:2;
}
```

And then have bitfields that aren’t extern(C) be illegal until 
the semantics are worked out. For example, [Adam’s 
ideas](http://dpldocs.info/this-week-in-d/Blog.Posted_2022_09_12.html#d-bitf
elds-could-be-good) could be good.

zjh <fqbqrr 163.com> writes:

On Tuesday, 18 October 2022 at 03:04:52 UTC, Dave P. wrote:
 [Adding bitfields to D]

For me, the more features, the better.

test123 <test123 gmail.com> writes:

On Tuesday, 18 October 2022 at 03:04:52 UTC, Dave P. wrote:
 [Adding bitfields to 
 D](https://dlang.org/changelog/2.101.0.html#dmd.bitfields) for 
 C interop is nice as it will automatically match the platform’s 
 ABI for bitfields, but I don’t understand why we would want the 
 implementation defined nightmare for regular D bitfields. One 
 of the most annoying things about C bitfields is that if you 
 use them,  you can’t just write your structs to disk or across 
 the network as your format is immediately non-portable across 
 different systems. That sucks as that’s exactly when you would 
 want to save space with bitfields. Native D bitfields should 
 avoid this problem.

 [...]

With d CTFE reflection, this is easy to workaround.