static static

[Andrei Alexandrescu]

Yigal Chripun wrote:
> bearophile wrote:
>> Yigal Chripun:
>>
>>> Regardless of usefulness (or good design) of such variables, this sounds
>>> extremely dangerous. The compiler must not change semantics of the
>>> program based on optimization. optimizing away such variables most
>>> definitely alters the semantics.
>>
>> Maybe you have misunderstood, or I have explained the things badly. So 
>> I explain again.
>>
>> I have seen that LDC (when it performs link-time optimization, that's 
>> not done in all situations) keeps just one copy of constants inside 
>> the binary even if such constants are present in more than one 
>> template instance. In the situations where LTO is available I think 
>> this doesn't cause problems.
>>
>> Then I am half-seriously proposing a syntax like:
>> T foo(T)(T x) {
>>   static static int y;
>>   // ...
>> }
>>
>> Where the y is now static to (shared among) all instances of the 
>> templated function foo. This may be a little error-prone and maybe not 
>> that useful, but again here the compiler doesn't change the semantics 
>> of the program, because using a double static keyword the programmer 
>> has stated such intention.
>>
>> Bye,
>> bearophile
> 
> Oh. ok. I seems I completely misunderstood you. It wasn't clear to me 
> before that your were talking about constants. Of course it's perfectly 
> OK to optimize _constants_ like that.
> 
> IMO, static is harmful and should be avoided. some newer languages 
> recognize this and completely remove this from the language. I'd like to 
> see D going in that path rather than adding even more ways to use static.
> 
> regarding your concrete proposal - as others said, you can use global 
> variables for that or put this inside a struct if you want to limit the 
> scope.

One option that hasn't been mentioned:

private ref int myInt() {
     static int theInt;
     return theInt;
}

void fun(T)(T arg) {
     ... use myInt() ...
}


Andrei