Re: [Boost-users] [mpl] what is not a placeholder expression

From: JOAQUIN LOPEZ MU?Z (joaquin_at_[hidden])
Date: 2007-07-29 07:49:26

----- Mensaje original -----
De: Aleksey Gurtovoy <agurtovoy_at_[hidden]>
Fecha: Sábado, Julio 28, 2007 11:14 pm
Asunto: Re: [Boost-users] [mpl] what is not a placeholder expression
Para: boost-users_at_[hidden]

> 
> ""JOAQUIN LOPEZ MU?Z"" <joaquin_at_[hidden]> wrote in message 
[...]
> > 1. Whether I'm right in assuming that the code above
> > should compile without assertion failures.
> 
> Yes.
> 
> > 2. What the behavior is for other versions of GCC and
> > compilers: reports most welcome!!
> 
> Basically, this is a GCC-specific problem caused by a
> non-conforming extension that was removed in 4.2.0
> (http://gcc.gnu.org/gcc-4.2/changes.html, search for
> "(undocumented) extension").
> 
> > 3. Whether this is a known problem specific to GCC
> > or, more generally, what the status of this issue is.
> 
> It is, and it's not a issue anymore starting with GCC 4.2.
> You should be able to work around it for older versions
> by providing a specialization of the
> 'boost::mpl::aux::template_arity' template along the
> following lines (untested):
> 
>    template<typename T,int n>
>    struct template_arity<foo<T,n> > : int_<-1> {};

Thank you thank you thank you for the very precise
and authoritative information! 

Best regards,

Joaquín M López Muñoz
Telefónica, Investigación y Desarrollo