Formatting strings using safe printf-like functions

The printf family of functions is a threat to security. It is a very bad design to allow users to put their own strings as a type and format the specifiers. So what do we do when user-defined format is required? How shall we implement the std::string to_string(const std::string& format_specifier) const; member function of the following class?

class i_hold_some_internals 
{
    int i;
    std::string s;
    char c;
    // ...
}; 

Getting ready

Basic knowledge of standard library is more than enough for this recipe.

How to do it...

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