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

29 Jul 2007

      ----- Mensaje original -----
De: Aleksey Gurtovoy 
Fecha: Sábado, Julio 28, 2007 11:14 pm
Asunto: Re: [Boost-users] [mpl] what is not a placeholder expression
Para: boost-users@lists.boost.org
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""JOAQUIN LOPEZ MU?Z""  wrote in message
[...]
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1. Whether I'm right in assuming that the code above
should compile without assertion failures.
Yes.
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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").
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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
   struct template_arity > : 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