Why does calling c_str() on a function that returns a string not work?

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SomeFunction().c_str() gives you a pointer to a temporary(the automatic variable str in the body of SomeFunction). Unlike with references, the lifetime of temporaries isn’t extended in this case and you end up with charArray being a dangling pointer explaining the garbage value you see later on when you try to use charArray.

On the other hand, when you do 

string str_copy = SomeFunction();

str_copy is a copy of the return value of SomeFunction(). Calling c_str() on it now gives you a pointer to valid data.

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