Discussion

Once you go const, you (should) never go back. If you cast away const on an object whose original definition really did define it to be const, all bets are off and you are in undefined behavior land. For example, compilers can (and do) put constant data into ROM or write-protected RAM pages. Casting away const from such a truly const object is a punishable lie, and often manifests as a memory fault.

Even when it doesn't crash your program, casting away const is a broken promise and doesn't do what many expect. For example, this doesn't allocate a variable-sized array:

void Foolish( unsigned int n ) {


 const unsigned int size = 1;


 const_cast<unsigned int&>(size) = n;   // bad: don't do this


 char buffer[size];                       // will always have size 1


 // …


}

C++ has one implicit const_cast, the "conversion of death" from a string literal to char*:

char* weird = "Trick or treat?";

The compiler performs a silent const_cast from const char[16] to char*. This was allowed for compatibility with C APIs, but it's a hole in C++'s type system. String literals are ROM-able, and trying to modify the string is liable to cause a memory fault.