boost::any test code compiles with Sun CC but not g++

Question

The following noddy test code:

#include <iostream>
#include <list>
#include <boost/any.hpp>
#include <boost/foreach.hpp>
#include <typeinfo.h>

using boost::any_cast;
using std::cout;
using std::cerr;
typedef std::list<boost::any> many;

template <typename T>
inline bool is_any(const boost::any& op)
{
  return (op.type() == typeid(T));
}

int main()
{
  many theStrangeList;
  theStrangeList.push_back("Can you really...");
  theStrangeList.push_back(std::string ("do random types in 1 container?"));
  theStrangeList.push_back(6.359);
  theStrangeList.push_back(7);

  BOOST_FOREACH(boost::any a, theStrangeList)
    {
      try
        {
          if (is_any<const char*>(a))
            {
              cout << any_cast<const char*>(a) << '\n';
            }
          else if (is_any<std::string>(a))
            {
              cout << any_cast<std::string>(a) << '\n';
            }
          else if (is_any<double>(a))
            {
              cout << "double = " << any_cast<double>(a) << '\n';
            }

        }
      catch (const boost::bad_any_cast& e)
        {
          cerr << e.what();
          cerr << "\n";
        }
    }


  return 0;
}

Compiles and works fine using Sun's CC compiler and default settings. However when using g++ I get the following :

$ g++ -I$BOOST_ROOT -o myany myany.cpp
myany.cpp:5:22: typeinfo.h: No such file or directory
/ilx/boost_1_41_0/boost/any.hpp: In constructor `boost::any::holder<ValueType>::holder(const ValueType&) [with ValueType = char[18]]':
/ilx/boost_1_41_0/boost/any.hpp:47:   instantiated from `boost::any::any(const ValueType&) [with ValueType = char[18]]'
myany.cpp:21:   instantiated from here
/ilx/boost_1_41_0/boost/any.hpp:122: error: ISO C++ forbids assignment of arrays

This is g++ version 3.4.3, so it might be different on a 4.x version, I'll try it later. Is this the reason why there isn't a 'is_any' template included with boost any, or is it a compiler bug?

I get the same result if I remove the template, as you would expect with an inlined function.

(related question)

Answer 1

Seems I only answered the second part of the question, so here I go with the first part as well:

Is this the reason why there isn't a 'is_any' template included with boost any?

There are no actual need to is_any, do the following instead:

if (const std::string* s = boost::any_cast<std::string>(&a))
{
   std::cout << "string = " << *s << '\n';
}
else if (const double* d = boost::any_cast<double>(&a))
{
   std::cout << "double = " << *d << '\n';
}

But this isn't extensible, prefer using boost::variant instead.

Is it a compiler bug?

It is a compiler bug in Sun CC. gcc is correct, the type of "Can you really..." is char[18], which doesn't satisfy the requirements of boost::any:

• A ValueType is CopyConstructible.
• A ValueType is optionally Assignable. The strong exception-safety guarantee is required for all forms of assignment.
• The destructor for a ValueType upholds the no-throw exception-safety guarantee.

Answer 2

For the first error try

#include <typeinfo>

not

#include <typeinfo.h>