Re: [Boost-users] [labmda & function] strange assembly errors with anunsupported compiler

From: Peter Dimov (pdimov_at_[hidden])
Date: 2007-01-07 16:51:58

Server Levent Yilmaz wrote:

> // A function object generator.
> // It returns a functor which in turn returns some
> // double member of A accessed via address offset
> boost::function<double(const A&)> getmem
> (
> const A* obj,
> const double* mem
> )
> {
>  ptrdiff_t shift = mem -
>     reinterpret_cast<const double*>(obj);
>  using namespace boost::lambda;
>  return *(ll_reinterpret_cast<const double*>(&_1)
>   + constant(shift) );
> }

This definitely sounds like a compiler bug. But your code isn't quite 
standard-conforming. You ought to use a pointer to member, not 
reinterpret_cast tricks.

boost::function<double(const A&)> getmem( double A::* pm )
{
    return pm;
}

> int main()
> {
>  A obj;
>   obj.a = 1.;
>  obj.b = 2.;
>  //
>  foo( getmem(&obj, &obj.b), obj );

    foo( getmem( &A::b ), obj );

> }