Non compile time evaluation for initializers

[Max Samukha]

On Fri, 26 Oct 2007 15:45:45 +0200, Lutger
<lutger.blijdestijn at gmail.com> wrote:

>Max Samukha wrote:
>> On Fri, 26 Oct 2007 10:52:25 +0200, Lutger
>> <lutger.blijdestijn at gmail.com> wrote:
>> 
>>> Lutger wrote:
>>>> Janice Caron wrote:
>>> ...
>>>> Suppose this is implemented, then how can you achieve constant folding 
>>>> with CTFE in initializers? Since it is not a compile time context 
>>>> anymore, all functions that substitue y will be evaluated at runtime.
>>> Nevermind, I responded too soon and overlooked the proviso that it's 
>>> only rewritten when it doesn't compile, sorry.
>> 
>> Then if a compile time function is messed up in a way that makes it
>> unevaluatable at compile time, it would be silently used at run-time,
>> which is not desired?
>
>Hmm yes, it's still an issue. Some functions are quite inefficient for 
>example if they are made to be evaluated at compile time, which doesn't 
>matter in that context but does for the runtime case.

As Reiner mentioned, the problem is that static variables should not
be initialized at compile-time at all. If you want CTFE put the
initializers in const context.

int foo()
{
   return 1;
}

static int x = foo; // module scope, static is optional; foo would be
evaluated on module construction

class C
{
   static x = foo; // ditto
}

void bar()
{
  static x = foo; // ditto
}

Then 'static' keyword here would mean 'global' and compile time
constructs would have to be changed to 'const if', 'const assert', etc
(Don't beat me please!)