What is std::safe_string?

Question

An answer to one of my questions included the following line of code:

label = std::safe_string(name); // label is a std::string

The intent seems to be a wrapper around a string literal (so presumably no allocation takes place). I've never heard of safe_string and neither, apparently, has google (nor could I find it in the 98 standard).

Does anyone know what this is about?

Answer 1

There is no such thing as std::safe_string

Answer 2

There is no standard safe_string. The safe_string you're seeing in that answerer's response is from what looks like a private STL extensions utility library.

Google for "stlext/stringext.h" and you'll see the same library referenced in a post on another forum.

Answer 3

After searching google code search (I should have thought of this first...) I found this:

//tools-cgi.cpp
string safe_string (const char * s)
{
    return (s != NULL) ? s : "";
}

Which converts NULLs to zero length strings. Although this is not standard it's probably some sort of extension in a specific STL implementation which was referred to in the answer.

Answer 4

It is not part of C++ standard (but perhaps it should be?)

I have been using the same kind of helper function to avoid a std::string throw an exception with a NULL char * string. But it was more something like:

// defined somewhere else as ""
extern const char * const g_strEmptyString ;

inline const char * safe_string(const char * p)
{
   return (p) ? (p) : (g_strEmptyString) ;
}

No overhead, and no crash of a std::string when I feed it a char * string that could be NULL but that, in that particular case, should behave as an empty string.