Re: Checking if a structs .init value is zero bits only

[Per Nordlöw via Digitalmars-d-learn]

On Wednesday, 28 March 2018 at 00:50:31 UTC, Ali Çehreli wrote:

On 03/27/2018 05:15 PM, Per Nordlöw wrote:

Is there a way to check if a struct `S` can be initialized using zero bits only, so that we can allocate and initialize an array of `S` in one go using `calloc`? If not, what should such a trait look like?

The following idea should work. One question that I'm not certain about is whether padding bytes inside .init can ever be non-zero in D. I assumed they are always zero. If not, the same idea must be applied recursively to individual members.

bool allZeros(T)() {
    // Yes, this can be implemented as a range algorithm. :)
    T t;
    foreach (b; (cast(ubyte*)&t)[0..T.sizeof]) {
        if (b) {
            return false;
        }
    }
    return true;
}

Yes, of course, thanks.

But my goal is (always) to have it done at compile-time.