strdup allocates a copy of the string on the heap, which you have to free manually later (with free() I think). If you have the option, it would be much better to return std::string. The static storage of out doesn’t help, because .str() returns a temporary std::string, which is destroyed when the function exits.
The documentation is correct. Use c_str() if you want a null terminated string. If the implementers happend to implement data() in terms of c_str() you don’t have to worry, still use data() if you don’t need the string to be null terminated, in some implementation it may turn out to perform better than c_str(). strings … Read more
The c_str() result becomes invalid if the std::string is destroyed or if a non-const member function of the string is called. So, usually you will want to make a copy of it if you need to keep it around. In the case of your example, it appears that the results of c_str() are used safely, … Read more