Recursive expansion

[bearophile]

Jonathan M Davis:

> I believe that if a particular template is ever instantiated 
> more than 50
> times recursively, the compiler will error out on the 
> assumption that it's hit
> infinite recursion (it has to bottom out eventually, or would 
> just end up
> running until it ran out of memory if it actually does hit 
> infinite recursion;
> I don't know how arbitrary the choice of 50 was).

I think currently the limit is 500 (time ago it was smaller, but 
probably higher than 50):


template Foo(int n) {
     enum Foo = Foo!(n + 1);
}
pragma(msg, Foo!0);
void main() {}


It gives:
test2.d(2): Error: template instance test2.Foo!(500) recursive 
expansion

The 500 limit is quite arbitrary. I like GCC, that defined a 
limit, but with
-ftemplate-depth-n you are allowed to increase it to n.

Bye,
bearophile