Is there a way to tell D to rearrange struct members or to not rearrange class members?

[Dejan Lekic]

On Friday, 27 June 2025 at 19:55:30 UTC, WraithGlade wrote:
> orthogonal to what I'm asking about. The Andrei book says that 
> D automatically rearranges members of `class`s in memory to 
> avoid wasting memory due to padding between members whose width 
> is less than the native CPU word size alignment, whereas 
> `struct`s are left as is (meaning the members aren't reordered 
> for alignment padding optimization).

So you were talking specifically about classes...

 From the https://dlang.org/spec/class.html#fields section:

> Implementation Defined: The D compiler is free to rearrange the 
> order of fields in a class to optimally pack them. Consider the 
> fields much like the local variables in a function - the 
> compiler assigns some to registers and shuffles others around 
> all to get the optimal stack frame layout. This frees the code 
> designer to organize the fields in a manner that makes the code 
> more readable rather than being forced to organize it according 
> to machine optimization rules. Explicit control of field layout 
> is provided by struct/union types, not classes.