Alisdair,

on Tue, 28 Nov 2023 17:07:44 +0700 you (Alisdair Meredith via Ext
<ext_at_[hidden]>) wrote:

> There is also the issue that `offsetof` returns an interesting value,
> but cannot be used to access the data member at that offset by any
> valid pointer arithmetic from the address of the complete object
> itself.

In C++ this might be subtly different, but the model in C is that if
you convert a pointer to the complete object to `unsigned char*`, this
gives you a valid pointer to an array that spans the whole object.
Within this array you can use the offsets that this macro provides.

Thanks
Jₑₙₛ

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