On Wednesday, 5 June 2024 at 18:31:12 UTC, Basile B. wrote:
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:
```d
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][1] 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.
[1]: https://dlang.org/spec/function.html#safe-values
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.
I don’t think there’s any meaningful difference. If a program has
UB, it can do anything, including corrupt memory. If a program
corrupts memory, that’s UB. `@safe` means UB-free, which includes
free of memory corruption.
