Re: Packing of Struct Fields

[Adam D. Ruppe via Digitalmars-d-learn]

On Saturday, 17 October 2020 at 13:00:59 UTC, Per Nordlöw wrote:
I understand that. I don't want the alignment of `S` to change. 
I want the padding after `s`

That padding is part of S. It is at the end, after its fields, 
but still part of it.

S's layout doesn't depend on what else is around it.

in `T` to be avoided and have `c` start at byte-offset 7.

Use a union.

    struct S
    {
        int i;                  // 4 bytes
        short s;                // 2 byte
        bool b;                 // 1 byte
    }
    static assert(S.sizeof == 8);
    static assert(S.alignof == 4);

struct T {
   union {
       S s;
       struct {
           align(1):
           ubyte[7] _ignore_me;
           char c;
       }
   }
}

static assert(T.alignof == 4);
static assert(T.sizeof == 8);
static assert(T.c.offsetof == 7);