On Wednesday, 5 June 2024 at 01:18:06 UTC, Paul Backus wrote:
>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
}
[...]
>Do I corrupt memory here or not ?
Is that a safety violation ?
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.
Obviously the topic was created because of the recent move D made. Sorry for the "catchy" aspect BTW. Now I remember that D safety is unrelated to undefined behaviors.