void main(string[] args)
{
    ushort a = 0b1111111111111111;
    bool* b = cast(bool*)&a;
    setIt(*b);
    assert(a == 0b1111111100000000); // what actually happens
    assert(a == 0b1111111111111110); // what would be safe
}

Do I corrupt memory here or not ?
Is that a safety violation ?

On Tuesday, 4 June 2024 at 16:58:50 UTC, Basile B. wrote:

void main(string[] args)
{
    ushort a = 0b1111111111111111;
    bool* b = cast(bool*)&a;
    setIt(*b);
    assert(a == 0b1111111100000000); // what actually happens
    assert(a == 0b1111111111111110); // what would be safe
}

[...]

cast(bool*)&a is a safety violation.

The only safe values for a bool are 0 (false) and 1 (true). By creating a bool* that points to a different value, you have violated the language's safety invariants. Because of this, operations that would normally be safe (reading or writing through the bool*) may now result in undefined behavior.