Linxutopia - Thinking in C++ - 3: The C in C++

Thinking in C++
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const_cast

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If you want to convert from a const to a nonconst or from a volatile to a nonvolatile, you use const_cast. This is the only conversion allowed with const_cast; if any other conversion is involved it must be done using a separate expression or you’ll get a compile-time error.

//: C03:const_cast.cpp
int main() {
  const int i = 0;
  int* j = (int*)&i; // Deprecated form
  j  = const_cast<int*>(&i); // Preferred
  // Can't do simultaneous additional casting:
//! long* l = const_cast<long*>(&i); // Error
  volatile int k = 0;
  int* u = const_cast<int*>(&k);
} ///:~

If you take the address of a const object, you produce a pointer to a const, and this cannot be assigned to a nonconst pointer without a cast. The old-style cast will accomplish this, but the const_cast is the appropriate one to use. The same holds true for volatile.

Thinking in C++
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