checkedint call removal

[John Colvin via Digitalmars-d]

On Wednesday, 30 July 2014 at 15:49:33 UTC, Daniel Murphy wrote:
> "Tofu Ninja"  wrote in message 
> news:dtjqnyucskwnqjvksawg at forum.dlang.org...
>
>> Question?
>> If an if condition throws or returns in its body is it ok for 
>> the optimizer to 'assume' that the condition is false after 
>> and make optimizations for it? If so then every one 
>> complaining that assert gets removed in -release should really 
>> just be using enforce.
>
> Yes.  In fact, it's required that an optimizer do this in order 
> not to be considered garbage.
>
>> The possibility for the optimizer to make the same 
>> optimizations for assert can be done for enforce, the only 
>> difference is that it does not get removed in -release....
>
> Not quite.  With enforce, it is impossible (ignoring hardware 
> or optimizer errors) for the condition to be false if the 
> enforce was not triggered. Because the assert is not checked, 
> the condition could be false and the code could do something 
> awful.
>
> Also, the optimizer can only use the enforce's assumption 
> _after_ it has checked the condition.  Since with assert it 
> doesn't need to check, it can go backwards and assume the 
> previous code will never produce a value that can violate the 
> assertion.
>
> if (y > 7) // x can't possibly be >= 5, so this can't be true
>  x = y + 1;
> assert(x < 5);
>
> if (y > 7) // the program will throw if >= 5, but that doesn't 
> mean it can't be true
>  x = y + 1;
> enforce(x < 5);
>
> Assert is much much more powerful.

So what is the recommended way of inserting a check of the sort 
that Ola would like?

debug enforce(expr);

perhaps? Seeing as that statement is completely missing outside 
of debug mode, the compiler can't do anything much about it.


P.S. What about version(assert)? Could the optimiser work with 
this:

if(x > 7) x++;
version(assert) auto testResult = x;
assert(x <= 7);