DIP60: @nogc attribute

[Dicebot via Digitalmars-d]

On Friday, 25 April 2014 at 15:29:38 UTC, Steven Schveighoffer 
wrote:
> On Fri, 25 Apr 2014 11:12:54 -0400, Dicebot <public at dicebot.lv>
>> Which is the very reason why I was so insisting of defining 
>> exact set of cases when optimisation is to be guaranteed in 
>> spec (before releasing @nogc). Unfortunately, with no success.
>
> Well, @nogc is not released yet. Please tell me we don't have 
> to avoid breaking code based on git HEAD...

It has become a blocker for next release though. It has been 
repeated numerous times that such features need to be developed 
in own feature branches until design is considered at least 
somewhat solid =/

>>
>>> But what really is the difference between a function that is 
>>> marked as @nogc that compiles on compiler X but not compiler 
>>> Y, and some custom attribute that compiles on X but not Y?
>>
>> There are no user-defined attributes that can possibly fail on 
>> only some compiler. And compiler-specific attributes are part 
>> of that compiler documentation and never part of language 
>> spec. This is the difference.
>
> But such a situation would not violate a spec that says "@nogc 
> means there are no hidden GC calls." And the end result is 
> identical -- I must compile function foo on compiler X only.

It is invalid and useless spec on its own. It would have been a 
valid spec if it also had a chapter with definitive list of all 
cases when hidden GC calls can happen and when are guaranteed to 
be optimized away. Otherwise such spec is as useful as one that 
says "Maybe your code will compile".

> I agree there are likely no precedents for this.
>
> Another option would be to put such a compiler-specific 
> attribute around the code in question rather than a different 
> attribute than @nogc on the function itself. I think there's 
> really no avoiding that this will happen some way or another.

I think there should be both. Saying that you need to marry 
specific compiler forever once you want to use @nogc is pretty 
much same as saying "don't use @nogc".