@noreturn?

[Timon Gehr]

On 05/15/2012 12:14 AM, Alex Rønne Petersen wrote:
> On 14-05-2012 23:59, Timon Gehr wrote:
>> On 05/13/2012 06:13 PM, Alex Rønne Petersen wrote:
>>> Hi,
>>>
>>> If memory serves me right, there were some proposals in the past to add
>>> a @noreturn attribute to the language. Where did this go?
>>>
>>> In writing unwinding mechanisms for my VM, I find myself actually
>>> needing some sort of @noreturn function attribute that would tell the
>>> compiler that the function does not return, rather than having to insert
>>> an assert(false); statement.
>>>
>>
>> What about making the compiler detect this pattern instead of adding an
>> attribute? I think it expresses exactly what you want to express, and it
>> does not require additional syntax.
>>
>> void foo()out{ assert(false); }body{ ... }
>
> While that might be an easier way to do it, I'm not sure if that would
> have unintended side-effects (admittedly, I can't think of any upfront).
>

Side effects:

- You wouldn't have to add the (completely redundant) assert(false) to 
the call site anymore.

- Ideally, the compiler will then optimize the code based on the 
pattern, namely, assertions that are unchecked in release mode. That may 
or may not be desirable.
  => Fix: Add 'hlt' to end of each method that has assert(false) out in 
release mode, and ban return statements from its body.

I think it could go either way, but having both @noreturn and out{ 
assert(false); } seems somewhat redundant to me.