Re: What's wrong with C++?

[Hyman Rosen <hyrosen@mail.com>]

On 10/6/2011 9:19 AM, Peter C. Chapin wrote:
> On Wed, 05 Oct 2011 04:13:22 +0200, Yannick Duchêne (Hibou57) wrote:
> The C++ compilers I've used where I've seen this happen (mostly while
> experimenting with metaprogramming) all produced an error message about
> "template instantiation depth exceeded" or something like that. None of
> them silently produced incorrect code.

I have unfortunately had the opposite experience with an older
version of Sun CC for Sparc. I was doing a kind of template
"recursion" as in the following code:

     struct Nil { };

     template <class First, class Rest>
     struct Cons { First first; Rest rest; };

     template <class T> void do_something(T) { }

     inline void apply_do_something(Nil) { }

     template <class First, class Rest>
     inline void apply_do_something(Cons<First, Rest> object)
     {
         do_something(object.first);
         apply_do_something(object.rest);
     }

The idea is that you build up a nested Cons structure of the
types you want to store, and then calling iterate on an object
of that type generates an inline expansion resulting in an
unrolled call of the do_something method on each field of the
structure, with no actual recursion at runtime.

Unfortunately, when my structure got nested too deeply, the
compiler silently terminated the recursion with an 'int'! It
took some strenuous debugging to figure that out, and I had to
abandon this approach altogether.