RE: [Boost-Users] Problem with BOOST_STATIC_ASSERT

From: Randy Bowen (rbowen_at_[hidden])
Date: 2003-01-07 19:21:08

Some further follow-up on this.  I've created a minimal program that
exhibits the new problem behavior:

/******************************************/
#include <boost/type_traits.hpp>
#include <boost/static_assert.hpp>

template < typename ValueType >
struct A
{
        BOOST_STATIC_ASSERT(boost::is_integral<ValueType>::value);
};

extern "C" int main(int argc, char* argv[])
{
        return 0;
}
/******************************************/

The fact that this assertion fails is counter-intuitive to me, since
there is no instantiation to compile.  Note that this behavior seems
limited to the use of "is_integral" as the type predicate.  Constructing
a similar program using "is_POD" behaves as expected:

/******************************************/
#include <boost/type_traits.hpp>
#include <boost/static_assert.hpp>

template < typename ValueType >
struct B
{
        BOOST_STATIC_ASSERT(boost::is_POD<ValueType>::value);
};

struct C {};

extern "C" int main(int argc, char* argv[])
{
        //	B<int> Bint;	/*  OK to add	*/
        //  B<C> BC;		/*  causes error	*/

        return 0;
}
/******************************************/

Here, no error occurs until there is an attempt to instantiate B<C>.

Randy Bowen

-----Original Message-----
From: Randy Bowen 
Sent: Tuesday, January 07, 2003 1:40 PM
To: Boost-Users_at_[hidden]
Subject: [Boost-Users] Problem with BOOST_STATIC_ASSERT

I'm in the process of updating some applications from use of Boost
1.28.0 to 1.29.0, using MSVC7.  I've noticed that a number of static
assertions that used to compile now generate errors.  The assertions all
use is_integral to perform a type validation - e.g.:

      BOOST_STATIC_ASSERT(::boost::is_integral<value_type>::value);

This produces an error of the form:

c:\Perforce\Development\Web\cppinclude\domestic\Application
Framework\State Machine Engine\StringSerializer.h(145) : error C2027:
use of undefined type 'boost::STATIC_ASSERTION_FAILURE<x>'
        with
        [
            x=false
        ]
        c:\Perforce\Development\Web\cppinclude\domestic\Application
Framework\State Machine Engine\StringSerializer.h(143) : see reference
to class template instantiation
'sme::StringSerializer<_StringType,>::StringWriter<<template
parameter>>' being compiled
        c:\Perforce\Development\Web\cppinclude\domestic\Application
Framework\State Machine Engine\StringSerializer.h(169) : see reference
to class template instantiation 'sme::StringSerializer<_StringType,>'
being compiled

I believe that the data type is integral, and is complete at compile
time.  Any known reason why this would happen?

Randy Bowen