DIP 1006 - Preliminary Review Round 1

[ag0aep6g]

On 03/07/2018 03:01 PM, Paolo Invernizzi wrote:
> On Wednesday, 7 March 2018 at 13:32:37 UTC, ag0aep6g wrote:
[...]
>> I don't think anyone is asking for that. The request is for no UB in 
>> @safe code.
> 
> Are we asking to statically check things like:
> 
> Assign Expressions [1]
> Undefined Behavior:
>    if the lvalue and rvalue have partially overlapping storage
>    if the lvalue and rvalue's storage overlaps exactly but the types are 
> different

If it can't be guaranteed that some code has defined behavior, then it's 
not allowed in an @safe function (or it should not be allowed). We are 
not asking for all valid code to be @safe.

Guaranteeing no UB is exactly @safe's purpose. The spec says: "Safe 
functions are functions that are statically checked to exhibit no 
possibility of undefined behavior." [1]

> Is that doable, in practise?

If you think that's not doable, what do you think @safe should aim for?


[1] https://dlang.org/spec/function.html#function-safety