Why does my C code, returning a string literal from a function, seem to work even though it\'s undefined behavior?

Understanding the Functionality of C String Literals in std::string Functions

In C , working with string objects presents certain nuances that require careful consideration. One such example is the use of C string literals within std::string functions, as demonstrated in the code snippet below:

<code class="cpp">std::string myFunction()
{
    return "it's me!!";
}</code>

Analysis of the Code

As you mentioned, the return statement in the std::string constructor implicitly initializes its internal string object with a const character array. The returned string object is then referenced by a temporary variable that gets deallocated upon the end of the function call.

However, subsequent uses of the string require access to its data. The c_str() method provides a pointer to the internal C-style string representation.

Understanding Undefined Behavior

Your concern about potential issues due to deallocating the string object is valid. In theory, the memory pointed to by the c_str() could be invalidated once the temporary string object is destroyed. However, in practice, the behavior observed differs.

The Role of the Operating System

The reason for this unexpected behavior lies in the role played by the operating system. When memory is de-allocated in C , the operating system doesn't always immediately erase its contents. Instead, it marks the memory as available for future use, making the contents still accessible temporarily.

Conclusion

While the code you provided may appear to work without errors, it falls under the category of undefined behavior in C . The exact outcome can vary depending on the specific operating system and runtime environment. To ensure robust and predictable code, it is important to follow best practices and avoid relying on undefined behavior.

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