Re: [Boost-bugs] [Boost C++ Libraries] #4109: xpressive compile error (MingW GCC 4.5)

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #4109: xpressive compile error (MingW GCC 4.5)
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2010-04-20 00:51:26

#4109: xpressive compile error (MingW GCC 4.5)
----------------------------------------+-----------------------------------
 Reporter:  Duzy Chan <duzy@…>          |       Owner:  eric_niebler
     Type:  Bugs                        |      Status:  assigned    
Milestone:  Boost 1.44.0                |   Component:  xpressive   
  Version:  Boost 1.42.0                |    Severity:  Problem     
 Keywords:  is_pure template_arity      |  
----------------------------------------+-----------------------------------
Changes (by eric_niebler):

  * keywords:  is_pure => is_pure template_arity

Comment:

 After a bit of digging, it seems the problem is actually in MPL (and by
 admission, in xpressive's reliance on an implementation detail of MPL).
 The following program, which compiles on gcc-4.4 but not on gcc-4.5,
 demonstrates the problem:

 {{{
   #include <boost/mpl/aux_/template_arity.hpp>
   #include <boost/mpl/aux_/lambda_arity_param.hpp>

   template<class A>
   struct T : A::x
   {};

   template<
     class T
     BOOST_MPL_AUX_LAMBDA_ARITY_PARAM(
       int Arity = boost::mpl::aux::template_arity<T>::value
     )
   >
   struct S
   {};

   template<template<class A> class P, class X>
   struct S<P<X> BOOST_MPL_AUX_LAMBDA_ARITY_PARAM(1)>
   {};

   int main()
   {
     S<T<int> > s0;
   }
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/4109#comment:7>
Boost C++ Libraries <http://www.boost.org/>
Boost provides free peer-reviewed portable C++ source libraries.