C++11: smart pointer

#include <memory>
#include <vector>
#include <string>
#include <iostream>
#include <stdexcept>

class StrBlob {
public:
typedef std::vector<std::string>::size_type size_type;
StrBlob();
StrBlob(std::initializer_list<std::string> il);
size_type size() const { return data->size(); }
bool empty() const { return data->empty(); }
void push_back(const std::string &t) { data->push_back(t); }
void pop_back();
std::string& front() const;
std::string& back() const;
private:
std::shared_ptr<std::vector<std::string> > data;
void check(size_type i, const std::string &msg) const;
};

int main()
{
StrBlob b1;
{
StrBlob b2 = {"a", "an", "the"};
b1 = b2;
b2.push_back("about");
}
while (b1.size() > 0) {
std::cout << b1.back() << " ";
b1.pop_back();
}
std::cout << "\n";
try {
std::cout << b1.back();
} catch (std::out_of_range &ex) {
std::cout << "file: " << __FILE__ << " line: " << __LINE__
<< " throw exception: " << ex.what() << std::endl;
}
std::cout << "aaaaaa\n";
return 0;
}

StrBlob::StrBlob(): data(std::make_shared<std::vector<std::string> >()) { }

StrBlob::StrBlob(std::initializer_list<std::string> il)
: data(std::make_shared<std::vector<std::string> >(il)) { }

void StrBlob::pop_back()
{
check(0, "pop back on empty StrBlog");
data->pop_back();
}

std::string& StrBlob::front() const
{
check(0, "front on empty StrBlob");
return data->front();
}

std::string& StrBlob::back() const
{
check(0, "back on empty StrBlob");
return data->back();
}

void StrBlob::check(size_type i, const std::string &msg) const
{
if (i >= data->size()) {
throw std::out_of_range(msg);
}
}

// C++ primer 5th exercise 12.2(p.458)
// g++ xx.cpp -std=c++11