overloaded operator for type conversion error

Here is what my operator looks like:

Code:

---

istring.hpp
---------------

operator char*() const;

---

Code:

---

istring.cpp
---------------

IString :: operator char*() const
{
    return ((string*)buffer)->data();
}

---

here string is the regular STL string. I get the following error when I try to compile this:

"/h/IString/istring.cpp", line 71.39: 1540-0258 (S) A return value of type "char *" cannot be initialized with an expression of type "const char *".
make: 1254-004 The error code from the last command is 1.

Any ideas?

>Any ideas?
The string type's data() member function returns a const qualified type. Instead of operator char *, why not use

Code:

---

operator const char*() const;

---