Converting std::basic_string into number... strange problem

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C++11

g++

Consider this code, compiled with g++ v.4.8.1-4 in Code::Blocks 10.05:

#ifndef ERROR_SAMPLE_H
#define ERROR_SAMPLE_H


#include <stdexcept>
#include <sstream>
#include <string>


// Class: my_traits_type
struct my_traits_type : public std::char_traits<char>
{};


// Class: my_string_type
using my_string_type=std::basic_string<char, my_traits_type>;


// Converts a std::basic_string<> into a T type.
template <typename T, typename CharT, typename Traits, typename Alloc>
T To(const std::basic_string<CharT, Traits, Alloc>& s)
{
	T value;

	std::basic_istringstream<CharT, Traits, Alloc> is(s);

	is >> value;

	if(!(is && (is >> std::ws).eof()))
	    throw std::invalid_argument("Function: To<>. Unallowed conversion.");

	return value;
}


#endif

and this simple main() function:

#include <iostream>
#include <string>
#include "error_sample.h"


int main()
{
	size_t value=0;

	std::string str_1("1");

	value=To<size_t>(str_1);

	std::cout << value << std::endl; // Prints 1.


	my_string_type my_string("1");

	value=To<size_t>(my_string); // Ouch! invalid_argument exception thrown.

	std::cout << value << std::endl;

	return 0;
}

If we now inspect into:

is >> value;

, we discover value equals to 2293515, in my case.

Can anybody explain what's going on here?

Thanks in advance.