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.
