Why Does Calling `c_str()` on a String-Returning Function Require an Intermediate Variable?

Understanding why c_str() on a String-Returning Function Requires an Intermediate Variable

In C , calling c_str() on a string to obtain a const char* pointer can be problematic if the string is returned directly from a function. This is because the returned string is a temporary object, and its lifetime ends once the function exits.

Consider the following code:

const char* charArray = SomeFunction().c_str();

In this scenario, charArray holds a pointer to the temporary object returned by SomeFunction(). When the function returns, the lifetime of the temporary object ends, leaving charArray dangling. Consequently, charArray stores garbage values.

To resolve this issue, an intermediate variable can be used to store the returned string before calling c_str(). This ensures that the string exists long enough for c_str() to obtain a valid pointer.

string str = SomeFunction();
const char* strConverted = str.c_str(); // strConverted stores the string's value properly

In this case, str is a local variable with longer lifetime than the function's temporary return object. When c_str() is called on str, it returns a pointer to the string's valid memory location, which is then stored in strConverted.

Therefore, it's crucial to use an intermediate variable when calling c_str() on a string returned from a function, as it ensures the availability of valid string data.

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