Re: Casting pointers

[Gary Willoughby via Digitalmars-d-learn]

On Wednesday, 26 August 2015 at 12:14:54 UTC, John Burton wrote:

This would be undefined behavior in c++ due to aliasing rules on pointers. It appears to "work" reliably in D when I try it, but that's obviously no guarantee that it's correct or will continue to do so.

Is this correct code in D? And if not, what should I do instead to cleanly and efficiently extract structured data from a sequence of bytes?

import std.stdio;

struct data
{
    int a;
    int b;
}

void main()
{
    byte[] x = [1, 2, 3, 4, 5, 6, 7, 8];

    data* ptr = cast(data*)(x);
    printf("%x %x\n", ptr.a, ptr.b);

}

This would perhaps be safer:

import std.stdio;

struct Data
{
    int a;
    int b;
}

void main()
{
    byte[] x = [1, 2, 3, 4, 5, 6, 7, 8];

    Data* data = cast(Data*)(x[0..Data.sizeof].ptr);
    printf("%x %x\n", data.a, data.b);
}