Search code examples
c++returncstringc-strings

Return an empty C-String

Simple Question:

How do you return an empty C-String with as little code as possible?

I have code that needs to return an empty char*. I am looking for something along the lines of return "";. I know there are several ways to do this, but I am looking for the most efficient way possible.

Using return ""; gives warning: conversion from string literal to 'char *' is deprecated [-Wdeprecated-writable-strings]

Thanks!

Solution

  • Short Answer:

    const char *get_string() { return ""; }

    or

    char *get_string() { return const_cast<char *>(""); }

    or 

    char *get_string() { return NULL; }

    or

    std::string get_string() { return std::string(); }


    Detailed Answer:

    Implicit conversion from string literal to char * is supported in C and C++98/C++03, but apparently not in C++11. The deprecation warning is just there to let you know that this should be addressed, particularly if you want to be able to migrate your code C++11.

    The empty string literal ("") is not actually empty, it is a string containing a single null character (\0). When you use return "";, you are actually returning a pointer to the memory location of the const string literal so the function return type should be const char *.

    If you really must return a non-const pointer to a string literal, you can use the const_cast operator to cast away the const.

    A better practice would be to return NULL (or nullptr) for functions that are returning empty, non-const, C-style strings, but only if the calling code is checking for NULL pointers.

    Note that C++ has its own string type (std::string), and an even better practice would be to use this rather than a C-style string when possible.